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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..0567c13 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #62008 (https://www.gutenberg.org/ebooks/62008) diff --git a/old/62008-0.txt b/old/62008-0.txt deleted file mode 100644 index dc441c3..0000000 --- a/old/62008-0.txt +++ /dev/null @@ -1,3484 +0,0 @@ -The Project Gutenberg EBook of Notes Upon Indigo, by John Hayes - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll -have to check the laws of the country where you are located before using -this ebook. - - - -Title: Notes Upon Indigo - -Author: John Hayes - -Release Date: May 3, 2020 [EBook #62008] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK NOTES UPON INDIGO *** - - - - -Produced by Ronald Grenier. (This file was produced from -images generously made available by The Internet Archive) - - - - - - - - - -Transcriber’s Notes: - -1. Footnotes have been moved to immediately after the associated - paragraph. - -2. Obvious typographical errors have been silently corrected. - -3. Spelling and hyphenation has been made consistent with the most - common usage. Quoted text from other works and authors was left - unchanged. - -4. Characters between underscores “_ _” are italicized. - - - - - NOTES UPON INDIGO. - - BY - - JOHN L. HAYES, - - - SECRETARY OF THE NATIONAL ASSOCIATION OF WOOL MANUFACTURERS, FELLOW - OF THE AMERICAN ACADEMY, AND CORRESPONDING MEMBER OF THE - ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA. - -From “The Bulletin of the National Association of Wool Manufacturers.” - - BOSTON: - - PRESS OF JOHN WILSON AND SON. - - 1873. - - -PART I. - -NOTES UPON INDIGO. - -PART I. - -A publication devoted to the interests of the woollen manufacture, -while giving due prominence to its first raw material, wool, cannot -neglect the secondary materials which enter into finished fabrics. The -attractiveness and utility of the largest class of these fabrics are -due to the hue given them by the dyer; and of all the coloring -materials one of the most precious is indigo. In former times, as it -still does at the East, it occupied with madder the place of one of -the two most important of all dyeing materials. Forced of late years -to give way to the marvellous products of modern chemistry, it will -doubtless resume its place under the influence of a more enlightened -economy and a more subdued taste. To contribute to the hastening of -this return is one object of this essay. The most usual reproach -against American fabrics is the want of stability in our dyes,—a -reproach without justice, if applied to American fabrics alone; for -the cheapening of dyestuffs is practised in all the so-called -manufacturing nations, and is contemned alone in the East, from which -we have derived our arts, and by the people whom we despise as -barbarous. To remove this reproach from American fabrics would be -worthy of no little temporary sacrifice on the part of our -manufacturers. - -The value of indigo as a dyeing material is due to the great stability -of the blue color, and the derivatives from blue, which it gives to -fabrics, especially of wool and cotton. It is not sufficient that a -dyed fabric should preserve its color when submitted to violent tests, -as when acted upon by vegetable or mineral acids or alkaline or soapy -baths: the only stable dyes are those which resist air and light, the -two destructive agents of vegetable colors. Indigo, from the -remarkable manner in which its color becomes fixed upon a fabric, to -be hereafter explained, possesses properties of resistance and -stability in a higher degree than any blue dye. And when we consider -that this blue has not only its own hue, but is the best foundation -for blacks, greens, purples, and even browns, the importance of these -properties cannot be over-estimated. Says M. de Kæppelin, a chemist -and manufacturer of Mulhouse, in one of a series of articles furnished -to the _Annales du gênie Civil_, 1864: “So high are the properties of -resistance and stability which indigo possesses, that it is perhaps to -be regretted for the art of the dyer and manufacturer of printed -calicoes, that the use of indigo becomes more and more rare, and that -the recent discoveries which modern science has placed at the service -of industry are daily eliminating it from our factories. I have -observed that whenever we have to dye stuffs of a high price, it is -indigo which always serves as a base for the foundation of all the -blue colors, or of those which are derived from blue. It is the same -for the fabrication of printed tissues, which serve for the poorer -classes, whose colors should have great stability without much -increase of cost. But of late years, especially, we find a tendency to -employ colors of little stability, and to prefer them, even in the -class of fabrics first referred to, to those which are more fast, on -account of their vivacity and freshness of tone. It is this tendency, -which the consumer partakes of even while complaining of it, that the -textile manufacturers ought to seek to combat. How often have I heard -the greatest manufacturers of Alsace deplore the obligation which they -felt that they were under of printing their tissues by means of colors -so fugacious and so little resistant as those composed from aniline. -We must hope, then, in the interest of that industry, that while -adopting the marvellous discoveries which science is every day making, -there shall be made a less general application of them, and that we -shall return to the fabrication of the styles which necessitate the -more constant employment of coloring materials,—less brilliant, it is -true, but more adherent to the tissues, and less alterable by air and -light. It seems to me, also, that taste would lose nothing; and that -printed stuffs, colored in a manner less brilliant, but more -harmonious, would be perhaps more appreciated, especially by those who -use them.” - -The tendency to substitute the brilliant for the stable dyes prevails -too much in our own manufacture. A very considerable cloth -manufacturer replied to our inquiry as to the extent to which he used -indigo: “I hardly use it at all; the dye of the indigo blue is not -bright enough to be popular.” On the other hand, we have heard our -leading manufacturer of carpets, whose cultivated taste has led him to -partake of M. de Kæppelin’s views, deplore the introduction of aniline -dyes, as a positive calamity to the textile industry. It is the -influence of the trade, the immediate consumers of fabrics, rather -than the judgment of manufacturers, which promotes the use of the -modern fugacious dyes. The dealers desire not only to imitate the -fashionable colors of European goods, but to secure the utmost -cheapness. One of our largest manufacturers of woollen goods, who had -made a special study of the best processes abroad, and was desirous of -bringing better dyed goods into more general consumption, urged one of -his largest customers, an extensive dealer, to allow him to dye the -waterproof cloakings which he was furnishing for his house, in fast -indigo colors, assuring him that he would charge simply the additional -cost of the indigo, without profit. The offer, which involved the cost -of only a few cents a yard, which would have been gladly paid by the -last consumer if the difference of value had been made known, was -declined. It is not improbable that the inferior goods which the -manufacturer was compelled to furnish were sold to the public as fast -dyed. Our manufacturers, therefore, may not have been responsible for -the predicament in which the most enthusiastic defender of our -protective policy found himself, as we have it from his own lips. -Being about to make a speech in Congress in defence of American -industries, he put on, for the first time, a coat declared to have -been made of American cloth. Sitting down, heated and perspiring from -the excitement of his effort, he found that beneath the arms whose -gestures had enforced his eulogies of American industry, the pretended -fast blue of his coat had become _red_, literally _blushing_ for its -unmerited praise. That fast-dyed goods of the highest excellence can -be and are furnished by American manufacturers, is shown by our army -cloths. The government specifications, copies of which are published -elsewhere in this number, require that all the blue woollen cloth, cap -cloth, and flannels furnished for the army shall be “pure indigo -dyed.” The requisition is strictly enforced. The admirable effect of -this regulation may be witnessed at any dress parade of a battalion of -United States soldiers. The persistency and uniformity of the hue -under constant wear—the cloth of the common soldier in its superior -dye often favorably contrasting with the finer but fancy dyed cloth of -the officer—is one of the circumstances which justify the assertion, -that our army is the best clothed in the world. The contrast is more -remarkable still with the _quondam_ blue cloth, converted by sun and -rain-into every shade of shabbiness, which we purchased in Europe for -our soldiers at the commencement of our late war. - - -ORIGIN AND EXTRACTION OF INDIGO. - -Indigo is a coloring material of vegetable origin, which owes its -color and its important applications to a direct blue principle, known -under the name of indigotine. It has been used as a dyestuff from time -immemorial, by the inhabitants of India; and it is from the East, the -cradle of the textile arts, that Europe has derived it. It was -probably received from India by the Greeks, among other products first -made known to them by the expeditions of Alexander the Great. -Dioscorides clearly refers to indigo in mentioning the two coloring -matters brought from India. Pliny mentions a coloring material, having -an admirable mixture of blue and purple, as coming from India, which -he calls _indicum_. That he refers to indigo is curiously manifest by -the test which he gives, by which the genuine drug might always and -_certainly be distinguished from the spurious_. This is by putting it -on live coals, when, says he, “the true _indicum_ will burn with a -flame of a most beautiful purple tint.” The purple vapor from burning -indigo is still a characteristic test. The Romans, it is apparent, -used indigo only as a pigment, not knowing what is still the most -important art connected with its use,—how to make it soluble so as to -be available in dyeing. - -That indigo as a commercial product was first obtained from India is -not only proved by the testimony of Pliny, and other ancient writers, -but is confirmed by a variety of circumstances, and particularly by -its name, which is known to have been _nil_ in the Hindu language, -from the earliest times of which there is mention of it. This name is -still given by the Hindoos to the color blue, and to all the plants -producing indigo. The Arabs and Egyptians, who obtained a knowledge of -indigo from India, adopted the Hindu name, the Arabs calling it _nil_ -or _nir_, and the Egyptians _nil_ or _niel_. The Portuguese preserved -the Indian name, with a slight modification, the substance being -called _aniliera_ in their language. The coloring substances -afterwards found in coal-tar having been first found in indigo, modern -science has adopted for them the name of _aniline_. - -It has been asserted that this substance was not known in Europe until -the time of the discovery of the passage to India round the Cape of -Good Hope. But Dr. Bancroft has shown that indigo was brought by -merchants from India to Alexandria, and thence to Venice, when that -city was the _entrepôt_ of Europe and the East. It doubtless -contributed to the excellence which the Italian states first attained -in the wool manufacture. The drug was called _endigo_ in Venice, and -it is from that city that we have derived its name and use. It was -imperfectly known in England under its Spanish name in the sixteenth -century, for we find in Hackluyt “Voyages” his instructions to a -traveller who was going to Turkey to ascertain “if _anile_, that -coloureth blue, be a natural commodity of those parts, and if it be -composed of an herbe.” - -The general introduction of indigo into Europe was impeded by -legislative enactments, prompted mainly by those employed in -industries which it threatened to displace. These were chiefly the -producers of and dealers in _woad_, formerly used exclusively for -dyeing blue, and the corporation of woad dyers. When dyers from Italy -and Flanders attempted to introduce the superior dyes of indigo, the -woad interests were sufficiently powerful to induce the Elector of -Saxony to denounce the use of the new dyestuff. It was pronounced in -the Diet of the Empire as “a corrosive color,” and “fit food only for -the devil,” _fressende teufels_. Similar propositions were made in -England and France, in which latter the free use of indigo was not -permitted until 1737. - -Although indigo as known in the arts is a product of vegetable origin, -we must not omit to notice that one source of its production is the -human body. It was discovered some years since that the blue color -sometimes found in diseased urines, and in certain suppurations, is -due to indigo. Dr. Schunck, in some papers read before the Royal -Society, has shown that it is a frequent constituent of urine secreted -by persons in a healthy state, and that, in fact, it is produced -generally when persons do not take sufficient exercise; and he has -several times succeeded in producing it by taking in his food a rather -large excess of sugar. He has found this substance also in the urine -of beef cattle. It must also be observed that the chemical actions of -indigotine with oxidizing agents, showing indigo to have a very close -relation to aniline and carbolic acid, both products derived from -coal-tar, have produced in the minds of chemists the conviction that -indigotine, like alizarine, the coloring principle of madder, will one -day be artificially produced from coal-tar. - -The plants which are known to furnish indigo are quite numerous, being -not less than sixty; they do not all belong to the same family, and -none of them contain the coloring principle already formed. The most -important belong to the leguminous family, from which most of the -vegetable dyes are derived, and to the genus _indigofera_. The species -cultivated and most esteemed are _Indigofera tinctoria_, _I. -disperma_, _I. anil_, _I. argentea_. - -[Illustration: Drawing of the Indigofera tinctoria plant] - -The principal source of the indigo of commerce is the _Indigofera -tinctoria_. The accompanying figure is a correct representation of the -plant, and we may dispense with a description of its botanical -characters, observing only that the plant has a half woody stem, and -rises to the height of from three to five feet. The plants exhale a -strong odor towards evening in the fields where they are cultivated. -The leaves have a disagreeable taste, and rapidly putrefy in water. -The plant originated in Campaja, or Guzerat, but is cultivated in -Hindostan, China, Java, and in the East Indies generally. It was -carried by the Spaniards to South America and the West Indies, and it -can be acclimated in all hot countries. The _Indigofera argentea_, or -indigo plant of Egypt, furnishes the indigo produced in that country -and Arabia. - -The culture of the plant and the production of commercial indigo is -carried on a vast scale in Lower Bengal. We have before us a large -map, placed at our disposal by an India merchant of Boston, showing -the location of each of the hundreds of factories of that important -centre of production. These factories have been developed by British -enterprise; and India thus receives some slight compensation for the -ruin of her cotton manufacture by the same influence. - -The propagation of the indigo plant in that country is made by sowing -in a thoroughly tilled silico-argillaceous soil. The seed of the plant -is sowed annually in the spring or autumn, according to the variety -used, some germinating more slowly, and requiring to remain in the -ground longer than others. The time of putting in the seed is also -governed by the nature of the soil and its position in respect to -neighboring rivers. In the lowlands subject to inundations, the indigo -ought to be all cut at the period of the rains and inundations, which -would destroy the crop in a brief time. Besides, during the rainy -period the planter has at his disposal sufficient water to commence -his operations of fabricating the indigo, which is the suitable time -for beginning the cutting of the plant. The time of cutting the -indigo plants is therefore regulated by the elevation of the land and -danger from floods. The high lands are always sowed several weeks -after those subject to inundations. - -The Chinese prick out the young plants in parallel rows, always -preserving the land quite clear of weeds. By taking away the blossoms -of the plant before their development, they increase the growth of the -leaves, and, consequently, the return of indigo; for it is in the -leaves principally that the coloring material is found. - -In certain localities the planters break off the leaves which have -acquired a bluish green tint. But more frequently the whole plant is -cut down close to the ground in the months of June or July, when the -flowers begin to open. The portion of the plant which remains pushes -up quite rapidly, and furnishes a second, and even third, and -sometimes, though rarely, a fourth cutting. The quality of the product -diminishes according to the number of the cuttings. - -The plant called _nil_, cut down to the root and gathered up in -packages, is worked up the same evening. The package is formed from -the product of a space of land embraced by a chain about three yards -long. The value of the first material changes with the value of the -soil. Thus, one soil produces a plant which has many stems and few -leaves, while another gives many leaves and few stems. The richness in -coloring material depends upon the quantity of leaves, but varies also -with an equal weight of leaves with atmospheric influences. Thus -regular dealers in the article observe a marked difference in the -quality of indigo in different seasons. - -M. A. Koechlin Schwartz has recently published some interesting notes -upon the preparation of indigo in Lower Bengal. In that country, which -furnishes excellent indigo, the factory includes, besides filters, -presses, a steam-engine, drying apparatus, and reservoir of water, two -lines of vats, arranged one above the other, from fifteen to twenty in -each line. These vats are built up with bricks, and covered with a -strong coat of solid and well made stucco. They are square, about six -yards on a side, and about a yard deep. The back row is about a yard -above the front one. The plant is fermented in the vats of the upper -row; when the operation of fermentation is terminated, a faucet is -opened, and the liquid is run into the lower vat. The water of the -Ganges, which is relatively pure, and thus well suited for this work, -is brought into basins of deposition, where it becomes clarified, and -is distributed by a common canal to the vats of the upper row. The -plants, cut in the morning and bound up into packages, come to the -factory after midday, and are thrown into the vat in the evening. A -vat contains one hundred packages carefully arranged, one beside the -other; heavy timbers are placed upon the plants, which are pressed -down by means of large wedges. It is necessary that the plants should -be pressed together very compactly, as without this the fermentation -does not take place to advantage. At nightfall the water is introduced -into the vats, and fills them so as completely to submerge the plants. -The fermentation is more or less prolonged according to the -temperature. Its duration varies from nine to fourteen hours. The -workmen judge as to the procedure of the operation by withdrawing a -little of the liquid in the lower vat. If it is of a clear pale yellow -when withdrawn, it will furnish a product less abundant but more pure -than if of a deep gold color. - -At the moment of its issue from the fermenting vat the liquid is of a -yellow color, more or less deep. The liquid is allowed to remain -undisturbed for a brief period, when twelve naked men, armed with long -bamboos, enter the vat to beat the water while it is still warm. -During this time the upper vat is emptied and cleaned out for the -succeeding operation. One vat requires seventeen workpeople (twelve -men and five women). They thrash the water for two or three hours. The -liquid passes by little and little to a pale green, and the indigo is -found on suspension in the form of small floccules. The liquor is -suffered to remain undisturbed for half an hour; it is then gradually -decanted by opening, one after the other, the discharging holes placed -at different heights. The water returns to the river, and the -precipitate, under the form of a thin _bouille_, is turned into a -reservoir. This _bouille_ is pumped up into a vessel, and made to boil -for a moment to prevent a second fermentation, which would injure the -quality of the product, by turning it black. It is suffered to rest -about twenty hours, and the next morning it is again subjected to -boiling, the ebullition being kept up three or four hours. The boiling -deposit is then turned off upon a large filter, through which the -water drips. This filter is composed of a vat constructed of masonry, -covered with stucco, about eighteen feet long by six feet wide and -three feet deep. This is covered with bamboos, upon which is a grating -of smaller reeds, and above by a stout strained cloth. There remains -upon the cloth a thick paste, of a deep blue and nearly black color. -The water which is run into the vat deposits some indigo which has -pressed through the filter. This is decanted after being allowed to -rest, and the turbid liquid is boiled the next day with the fresh -indigo. - -The paste of the filter is introduced into some small boxes of wood, -pierced with holes, and provided above and below with a strong cotton -cloth. The whole is again covered with a piece of stuff, and then with -a covering of wood, pierced with small holes, and it is placed under a -press, the force being gradually applied, so as to cause the water to -run out as much as possible. There is withdrawn from the box a cake of -the size of a cake of Marseilles soap. The water squeezed out flows -back into the filtering vat, to be boiled again with the fresh indigo. -The drying of the cakes ought to be done very slowly. - -The dry-house is a large building of masonry, quite high, and pierced -with many openings, provided with narrow blinds, to prevent the direct -light of the sun from penetrating into the interior. Care is taken -also to surround the dry-house with large shade-trees. The cakes take -from three to four days to dry, after which they are packed in small -boxes and carried to Calcutta, the great market of Bengal. - -The details above given apply to the factories managed by European -planters. The natives operate in nearly the same manner, but with less -care, and consequently their products are inferior. The average -product of indigo in Lower Bengal is stated at 4,000,000 kilograms, or -8,840,000 pounds per year. The most remarkable fact to be noticed in -these operations is, that the blue principle is developed by chemical -action from certain absolutely colorless principles existing in the -plant. The theory of the change effected is still somewhat in doubt, -because no chemist has studied the fresh plant, and observed upon the -spot the phases of the operation of the production of indigo on a -large scale. But the most accepted theory is that derived from the -researches of Dr. Schunck, upon the _isatis_ or woad-plant, which -produces indigotine in a much less degree than the true indigo plants; -viz., that the indigo exists in the plants combined with sugar, -forming a glucoside, to which he gives the name _indican_. This -compound, under the influence of fermentation in the manufacturing -process, is supposed to be unfolded into indigo and sugar. - -Without dwelling upon this question, which is beyond our province, we -observe that the plants of the genus _indigofera_ are used for the -production of commercial indigo, on account of the greater richness in -the coloring principle. Other plants, which furnish the same coloring -principle, indigotine, are more frequently used directly in dyeing to -furnish the blue principle than they are for the production of indigo. - -The most important of these plants, although there are others, such as -the _Polygonum tinctorium_ and the _Nerium tinctorium_, is the _Isatis -tinctoria_, which produces pastel, or woad. This, plant belongs to the -family of cruciferæ, and is a biennial. It is represented in the -accompanying figure. - -[Illustration: Drawing of the Isatis tinctoria plant] - -The leaves which surround the stem are collected in May or June of the -second year, when they begin to turn yellow. The wasted and dried -leaves are sometimes used directly for dyeing, but more generally the -leaves, after being cut and dried, are carried to a mill, and then -ground to a paste, after which it is formed into a mass or heap, and -being covered to protect it from rain, is left to undergo a partial -fermentation for about a fortnight. The heap is then well mixed and -formed into balls, which are exposed to the sun and wind to dry, and -thereby prevent the putrefaction which would otherwise take place. -Being afterwards collected in heaps, these balls again ferment, become -hot, and emit the odor of ammonia, which Hume tells us, in the History -of England, gave such offence to Queen Elizabeth that she issued an -edict to prohibit the cultivation of this plant. After the heat has -continued for some time, these balls fall into a dry powder, in which -form the woad is usually sold to the dyer. The best French woad comes -from Provence, Languedoc, and Normandy. In Germany, the pastel of -Thuringia is used almost exclusively; the packages have the trade-mark -of three towers, with the numbers 4, 5. In this country, owing -probably to the prejudices of practical dyers, who have generally come -from England, the Lancashire woad is almost exclusively used. The very -little imported of late years, ranging from two thousand to twelve -thousand dollars annually in value, is used for mixing with indigo in -the so-called woad vat, to be hereafter described. - - -COMMERCIAL INDIGOES. - -The following description of the indigoes of commerce is taken -principally from Schutzenberger’s excellent treatise on coloring -materials. It coincides very nearly with that given by Napier from -Dumas and Chevrueil. Indigoes are classed, according to their origin, -into three groups. - -1. Indigoes of Asia (from Bengal, Oude or Coromandel, Manilla, Madras, -and Java). - -2. Indigoes of Africa (Egypt, Island of France, Senegal). - -3. Indigoes of America (Guatemala, Caraccas, Mexico, Brazil, and the -West Indies). - -The three varieties in most esteem are those of Bengal, Java, and -Guatemala. - -_Indigoes of Java_.—These are distinguished by the great purity of -their coloring material. They contain the minimum of extractive -organic matter. If, in spite of this, they do not give a high yield of -indigotine; this is owing to a mixture of silicious mineral substances -with their paste. The paste is soft. It adheres strongly to the -tongue, and its density is feeble. They are generally of a pure blue, -light or ash colored in the kinds which are less rich, and of a -magnificent violet blue in the superior qualities. The last take a -beautiful copper color when scratched by the nail. They are placed in -the very first rank among all indigoes in respect to fineness and -beauty, if not in richness in the blue coloring principle. Their -purity, complete absence from carbonate of lime, and the small -quantity of foreign organic materials which they contain, cause them -to be much sought for, for the preparation of _carmine_ of indigo. The -consumption of the Javan indigoes in this country is so small as not -to be appreciated. - -_Bengal Indigoes_.—These are the indigoes _par excellence_, for in -them are found the most varied qualities, from the most beautiful and -rich to the most ordinary. The superior qualities are of a deep violet -blue, with a fine and uniform paste; they adhere to the tongue, are -easily pulverized, and take a beautiful coppery tint when scratched by -the nail. The fresh fracture shows a magnificent purplish blue -reflection. Their yield in indigotine does not surpass seventy-two per -cent. - -After these come the reddish-violet indigoes with a purplish hue, and -a fracture more uniform and shiny. They are also more dense and hard -than the superior qualities. The reddish hue does not proceed from the -greater or less amount of coloring material contained, but from the -presence of a greater quantity of brown and red extractive matter. -These qualities are not to be despised, for the kinds which give the -best results in the dyeing vat are found in these indigoes. It would -seem, in fact, says the author whom we are following, “that the browns -and reds of indigo play an important part in vat dyeing, that they are -able to become dissolved and to fix themselves upon the tissues at the -same time as the indigotine, and thus operate to reinforce the hue. -The fact is, that dyers generally prefer the reddish indigoes to the -other varieties.” Among the Bengal indigoes there is found a clear -blue variety, less rich in coloring matter, but also more exempt from -organic substances. The impurity is constituted by mineral matters. It -is less dense, adheres strongly to the tongue, and does not take a -coppery hue, like the other varieties, when scratched by the nail. - -The worst qualities of the Bengal indigoes, as in all the species, are -the clear blues, shading on to gray or green. This coloration denotes -a great quantity of extractive matter different from the indigo brown -which characterizes the red varieties, and completely inert. These -indigoes are hard, dense, adhere little or none to the tongue, and do -not show coppery reflections when scratched. - -The most skilful connoisseurs distinguish forty-three varieties of -Bengal indigo. The most important are the following:— - -1. _Superfine blue, light or floating_.—Color bright blue; light, -friable, and spongy; adherent to the tongue, soft to the touch, -showing coppery reflections when rubbed by the nail; paste uniform and -pure. - -2. _Fine blue_.—Like the preceding, but the color a little less vivid. - -3. _Violet blue_.—A little less light and friable. Has a violet blue. - -4. _Superfine violet_. - -5. _Superfine purple_. - -6. _Fine violet_. - -7. _Good violet_. - -8. _Red violet_. - -9. _Ordinary violet_. - -10. _Good soft red_. - -11. _Good red_. - -12. The indigoes, _fine coppery, good coppery, ordinary coppery, and -low coppery_. - -_The Indigoes of Oude and Coromandel_.—These are made in the interior -of Hindostan. Those of the best quality correspond to the middling -Bengal indigoes, and are met with in square masses, having an even -fracture, but are more difficult to break; the inferior qualities are -heavy, of a sandy feel, having a blue color, bordering on green or -gray, or even black; often in large squares, and covered with a slight -crust or rind of a greenish color. They are the most difficult to -break of all the indigoes of commerce. - -_Madras Indigoes_.—They have a grained fracture, and are of a cubical -figure. The superior qualities have no rind. The qualities are fine -blue, mixed violet blue, and ordinary. They are all lighter, and less -rich in coloring matter than the Bengal indigoes. - -_Manilla Indigoes_.—These occur in cubical blocks, flat squares, or in -irregular pieces. They are light, with a fine paste, and of a clear -blue. They effervesce with acids, showing the presence of carbonate of -lime incorporated in their paste. They are consequently poor in -coloring material, and are hence almost exclusively used as a bluing -material in washing fabrics. - -_American Indigoes_. _Guatemala_.—These indigoes are produced now -altogether in Hunduras, although they still retain in commerce the -name of Guatemalan. They are generally found in small pieces, -irregular in form and size, and come in envelopes of skin containing -about half as much as the Bengal chests. Putting aside the difference -in exterior form, these indigoes approach very closely to those of -Bengal. The same qualities are found, only they are more frequently -mixed. The clear blue is more rare, and, when it is found, it is -poorer in coloring matter. In purchasing these indigoes it is -necessary to beware of the reds, which often contain a strong -proportion of the brown extractive matter. It is not rare to find -among the Guatemalan indigoes beautiful specimens of the blue violet, -equal to the richest Bengal variety. Unfortunately, this superior -variety is generally mixed with inferior kinds, as to have less value. -The American indigoes are classified as follows:— - -_Guatemala floro_.—Bright blue, paste uniform, soft and light. This -variety, in Bancroft’s time, was the most esteemed of all indigoes. - -_Guatemala sobresaliente_.—Less light, the paste firmer and the blue -less beautiful. - -_Guatemala corte, or copper-colored_.—Paste less firm and heavier, -coppery red. - -_Caraccas_.—These resemble very much the Guatemala varieties. The -qualities are designated by analogous names, but they are, in general, -less esteemed than the preceding. - -_Mexican_.—They hold an intermediary rank between the Caraccas and -Mexican. - -_Brazil_.—These indigoes are in small rectangular parallele-piped -masses, or in irregular lumps of a greenish gray color externally, and -having a smooth fracture, a firm consistency, and a copper-colored -tint of greater or less brilliancy. - -_The indigoes of Africa and Egypt_.—These have only been manufactured -within the last twenty years; they are in flat squares. The paste is -fine and quite light, and the color pure blue or bordering on violet. -The varieties are distinguished as fine blue and good violet and red. - -_Indigoes of the Isle of France and Senegal_. Rare in commerce, but -of good quality. - -The indigoes of the inferior qualities, characterized by a salt-like -color, bordering more or less upon green; by a coarse, uneven, and -very dense paste; by not adhering to the tongue, and by not showing a -coppery color when scratched,—can never be employed to advantage, -notwithstanding their low price. The purchaser of these qualities must -be guided solely by the results of analysis; for an article is found -in commerce whose richness in indigotine does not exceed twelve to -fourteen per cent. The presence of so high a proportion of foreign -matter prevents the chemical change which the indigo ought to undergo -in the dyeing vat; and this foreign matter, added to the deposits of -the dyeing vats, causes great loss of the coloring matter. These -indigoes should be used as little as possible, especially in the cold -vats used for dyeing cotton and linen. The middle varieties of the -Bengal and Guatemala indigoes, and, above all, the red varieties, -produce in the cold vats the most advantageous results. The lower -qualities above spoken of present less inconvenience in the hot vats -used for dyeing wool; and it is for this purpose that they are -generally used. In considering the previous observations, the wool -manufacturer may arrive at this conclusion: that while he can, with -less loss than the maker of cotton fabrics, make use of the lowest -qualities of indigo, he will obtain _the best results from the middle -qualities of the reddish Bengal indigoes_. - -The skilled dealers in indigo recognize not only the above -distinctions, founded upon the country of production, color, and -physical qualities, but they observe whether the article has any of -the following defects, which are designated by certain well-understood -terms: such as whether the indigo is _sandy_,—when brilliant points -are observed in the interior, which are in reality particles of sand; -_spotted_, that is to say, of unequal tint, and marked by small -blackish points; _ribboned_, marked by transversal bands of a paler, -and sometimes red color; _burnt_, the pieces having a scorched -appearance, due to rapid drying, and separating into small black -fragments under the pressure of the hand; _crumbly_, when in pieces of -irregular figure, proceeding from fractures of the squares; _cold_, -when the indigo does not adhere to the tongue. The above -classification is presented with a full knowledge that these -distinctions are by no means recognized in the ordinary commerce in -this article. It is not, however, without interest as an illustration -of the minute attention given to this subject in Europe, where a -higher manufacture requires a nicer investigation of the qualities of -materials employed. - - -DETERMINATION OF THE RICHNESS AND PURITY OF INDIGOES. - -It is evident that the commercial form and the high price of this drug -favor fraud, and the desire to illicitly introduce foreign substances -into the paste. It is important, therefore, that the purchaser should -carefully ascertain the actual value of the article which he is to -use. He should know not only the proportion of indigotine contained, -which varies in the commercial indigoes from twelve to seventy-five -per cent, but the hardness and density. A good indigo ought to have -qualities which can be recognized by the eye and touch alone. The -first and the only examination ordinarily made by purchasers is in -respect to the physical qualities of the article. Different pieces are -selected, and their fresh fracture is attentively observed. The -purchaser observes whether the squares are like each other, and if the -parts of the same piece present the same tint. He determines the -porosity by the simple means of applying his tongue to the fresh -fracture. The more rapid the adherence of the tongue, the more porous -the indigo. By scratching the piece with his finger-nail, he -determines the extent of the coppery reflection,—an important test. - -From all these characters, taken together, the purchaser can form -quite a correct idea of the value of indigoes in general; and the -greater number of dyers, both in Europe and this country, are -satisfied to make their purchases with only this physical examination. -The most experienced dealers in this country make no other examination -than the physical one. An eminent indigo broker in Boston has -permitted me to copy the following memoranda for the physical -examination of indigo from his notebook. - -The chief signs of good indigo are its lightness, feeling dry when -touched, and, when broken, appearing of a beautiful violet blue. Good -indigo swims in water; if thrown upon burning coals it emits a -violet-colored smoke, and leaves but little ashes. - -In selecting indigo the large regularly formed cakes should be -preferred,—those of a fine, rich blue color, extremely free from the -white adhesive mould[1], and of a clean, neat shape. When broken, it -should be of a bright purple cast, of a close and compact texture, -free from specks or sand, and when rubbed with the nail should have a -beautiful shiny coppery appearance; when burnt in a candle it should -fly like dust; that which is heavy and dull colored should be -rejected. Indigo is estimated and classed in commercial language, as -follows: fine blue, ordinary blue, fine purple, inferior purple, and -violet, strong copper, and ordinary copper. It is purchased by the -factory maund (74⅔ lbs. The Bazaar maund is 82²⁄₅₀ lbs.), packed in -cases containing on an average 2¼ cwt., dammered (pitched) and covered -with gunny bagging. - - ------------------------------------------------------------- - [1] Many experienced purchasers in this country pay no regard to - this mould, as it weighs scarcely any thing.—Ed. - ------------------------------------------------------------- - -Still, in making large purchases, as a measure of wise precaution the -chemical test should be added. This is used to ascertain the -proportion per cent of indigotine which a given indigo has. The -determination of the quality of indigotine contained is not alone -sufficient to fix the value of an indigo. With an equal yield of -indigotine, the indigoes are always to be preferred which have a light -and soft paste; and for the preparation of the indigo vat the -preference should be always given to the violet red rather than to the -clear blue indigoes. - -The chemical works which treat of this subject give elaborate details -of a great number of processes for determining by chemical tests the -amount of indigotine, or the coloring material in indigoes. To give -these numerous processes would only confuse the reader. In our own -confusion upon this subject we submitted the descriptions of these -various processes to one of the most eminent and practical of American -chemists, Dr. Charles T. Jackson, an official State Assayer for the -State of Massachusetts, who has had much experience in testing indigo, -with a request that he would describe the process which he approves -and practises. He has obliged us by the following communication:— - - Boston, Nov. 21, 1872. - No. 47 Court Street, Room 4. - -John L. Hayes, Esq. - -Dear Sir,—In reply to your inquiry as to the simplest method of -analyzing indigo, I would say that I first ascertain the amount per -cent of earthy matters and metallic oxides, in the samples brought to -me, by burning a weighed quantity in a counterpoised platinum -crucible, until all organic matters are removed or consumed, and then -weighing the ashes obtained. The ash is then subjected to analysis in -the usual way, and lime, alumina, peroxide of iron, and some other -earthy impurities are separated. - -Then, to determine the amount of coloring matter, or indigotine, I -make use of a standard sample of pure reduced indigo, which is -dissolved in the most concentrated sulphuric acid, and diluted with -water after solution. Then I ascertain how much bleaching powder -(chloride of lime) is required to dissolve the solution. This is the -quantity required for absolutely pure indigo. - -Now, the indigo of commerce does not contain more than say from forty -or fifty per cent of pure indigotine, and of course will require a -smaller quantity of bleaching powder to decolor it; or the quantity of -bleaching powder to decolor a given weight of pure indigo may be -weighed out, and the sample to be compared having been dissolved in -strong sulphuric acid, and diluted with water, is to be poured in and -stirred or shaken well until the point of decoloration is ascertained. -In this case it is best to weigh out at least twice as much of the -sample to be tested as was used of pure indigo, and to measure the -solution in a graduated glass vessel,—an alkalimeter, for example,—so -that by measure we may know exactly how much of the sample we add to -the solution of bleaching powder. Thus the relative coloring values of -the samples may be readily ascertained. - -If you have no purified indigo on hand, you can make a good -comparative trial of your samples against a perfectly good sample of -Bengal indigo, which may be kept for a standard of comparison. Very -useful practical results may thus be obtained. - -It is well, however, to keep on hand a standard sample of pure indigo, -prepared from reduced or white indigo, as directed by Berzelius (vol. -vi. page 3, French ed., 1832), and in Muspratt’s Chemistry applied to -the Arts (Dyeing, Indigo). - -In the analysis by reduction of indigo, the process is simply as -follows: Reduce the indigo to fine powder, and weigh it; weigh out an -equal quantity of pure quicklime (made from pure white marble). -Measure in a graduated vessel a certain volume of water. Slack the -lime with a portion of this water. The rest of this water is to be -used in rubbing up the indigo in a mortar. Then the slacked lime is to -be mixed with the indigo, rubbing the substances well together. -Introduce the whole into a large flask; 1½ to 2 litres (about 3 to 4½ -pints) of water is required for 1 gramme (or about 15 grains of -indigo). The flask and contents are then to be exposed to a heat of -from 176° to 190° F. for some hours. This is best effected in a water -bath. By this digestion the lime is made to combine with the indigo -brown, and the coloring matter is set at liberty. Dissolve in the -liquor a little protosulphate of iron, exempt from copper, and reduced -to a fine powder. The flask is to be corked and well shaken, and -allowed to cool. When the sediment is settled, decant the clear -solution by means of a syphon into a graduated glass. The coloring -matter oxidizes by exposure to the air; and to favor this oxidation -and to keep the lime in solution, add muriatic acid to the liquor. -When the liquor has become clear, filter and collect the precipitate -on a weighed filter, which wash with hot water, and dry at a -temperature of 212° F. Thus we can learn, by weighing the filter -again, how much indigotine is contained in the sample. - -If we make use of 200 measures of water, and have drawn off 50 -measures of the solution to oxidate, and this 50 measures has produced -10 grains of indigo, the whole sample evidently contained 40 grains of -indigo blue. - -This method serves both for an assay of the sample and the production -of a standard sample of pure indigotine. The operation may be carried -on upon a larger scale for the manufacture of a standard sample. - -Yours truly, - -C. T. Jackson. - -Dr. Jackson adds the following note:— - -In the processes given I have not referred to the qualitative analysis -or testing for all the kinds of adulterations, but have given only -valuation of the coloring power of indigo. - -I have had occasion to search indigo for Prussian blue, an occasional -adulterant. This is ascertained by caustic potash, which becomes in -part an oxide if Prussian blue is present. This acidulates with -muriatic acid, and, tested with sulphate of iron, proves, by formation -of Prussian blue, the presence of the ferrocyanide of potash in the -solution, and hence Prussian blue in the indigo. Lime and clay are the -usual adulterants, and oxide of iron is often present accidentally or -from the clay adulterants. Starch and flour are rarely used, as they -add little to the weight. - -C. T. J. - - -COMMERCE IN INDIGO. - -Before proceeding to a consideration of the practical applications of -indigo in manufacturing, we must pause to make some general -observations upon the commerce in indigo. - -The first European impulse given to this commerce was made by the -Spanish and Portuguese. They not only imported indigo from the Indies, -but established its fabrication in their colonies. To them we owe its -production in Guatemala, Caraccas, and Brazil. The French exported -from the Island of San Domingo, only, in 1774, 2,350,000 pounds weight -of this commodity. British influence was exerted in favor of the -development of this article in the American colonies, and, in 1773, in -the space of twelve months, over a million pounds of indigo were -exported from South Carolina. The production in India was at that time -of little importance. It was not until 1783 that the attention of the -English was directed to the culture of indigo in India for European -consumption, that produced by the natives being all consumed in their -own manufactures. In the hands of the English this product rapidly -rose to be the most important of India, in a commercial view, except -that of rice. The small cost of a factory, and the comparatively small -capital required for this production, caused the indigo culture to be -preferred to sugar planting. The importation and sale of this -commodity at the East India House, in 1792, amounted to 581,827 lbs., -while the importation into Great Britain from other parts of the world -amounted to 1,285,927 lbs. In 1806 the importation from the East -Indies, and sales at the East India House, amounted to 4,811,700 lbs., -and produced in sterling money £1,685,275. In the year 1862–63, the -export from India, and the destination of supplies, were as follows:— - - Destination. Quantity. Value. - ---------------------------------------------------- - United Kingdom 8,537,133 lbs. $1,627,035 - America 134,064 26,949 - Arabian and Persian Gulfs 343,037 33,385 - France 1,922,120 371,396 - Germany 85,680 15,504 - Suez 295,269 51,730 - Other places 9,577 815 - ---------------------------------------------------- - Total 11,326,880 lbs. $2,126,814 - -The value of exports in 1866 was £1,861,501. In the same year the -imports of indigo from the whole of Central America, including -Honduras, was 672,480 lbs. The consumption of indigo in Great Britain -did not increase during the ten years ending with 1867. This -stationary demand, notwithstanding the fall in the price of the drug -and increase of population, is attributed by McCulloch principally to -the decreasing use of blue cloth. It is more probably due to the -substitution of cheaper dyes. The average home consumption in Great -Britain for seven years ending in 1867, was 1,675,072 lbs. per year. - -The importation into this country for the twenty years last past is -shown by the following table, kindly prepared at our request by the -chief of the Bureau of Statistics:— - -_Statement of Imports of Indigo into the United States during the -Fiscal Years ended June 30, 1853–1872._ - - INDIGO. - Fiscal - Year - ended - June 30 FREE OF DUTY. DUTIABLE. - -------------------------------------------------- - Pounds. Dollars. Pounds. Dollars. - 1853 1,387,847 947,367 - 1854 1,965,789 1,282,367 - 1855 2,097,397 1,151,516 - 1856 1,732,290 1,063,743 - 1857 1,533,037 1,010,509 - 1858 1,647,767 945,083 - 1859 1,773,868 1,441,429 - 1860 1,707,116 1,413,790 - 1861 185,039 160,138 719,563 505,766 - 1862 2,501,052 3,281,441 - 1863 885,834 1,008,187 178,364 219,169 - 1864 684,813 623,406 897,821 671,899 - 1865 741,438 601,283 415,575 324,207 - 1866 798,855 609,160 44,660 41,268 - 1867 1,069,506 816,974 - 1868 870,164 775,751 - 1869 1,574,449 1,649,550 - 1870 1,270,579 1,203,664 - 1871 1,994,172 2,052,222 - 1872 1,526,869 1,484,744 - - EDWARD YOUNG, _Chief of Bureau_. - Bureau of Statistics, Nov. 16, 1872. - -The extraordinary quantity imported in 1862, we hardly need remark, -was due to the demand for consumption in army cloths. Indigo imported -directly, was made free of duty in 1861. The duty which appears by the -above table to have been charged since that period, was upon indigo, -the product of India, imported by way of England, which was subject to -an extra duty of ten per cent. - -The indigo consumed in the United States is generally supplied by the -Boston and New York Calcutta houses, who have either an American -partner resident in Calcutta, or who employ a resident American as -agent. Indigo, like other Calcutta goods, is sold through the agency -of brokers, who receive on this article a commission of one per cent. -The value of the article is known almost daily in these cities by -telegrams, giving exact information of the state of the trade, -transmitted from Calcutta as often as every five days. Some of the -brokers publish monthly circulars, showing the stock of indigo with -other Calcutta goods on hand in our market. The regular trade reports -issued by the India merchants show that The higher qualities of indigo -do not come to our market. The following is an extract from a report -of Whitney, Brother, & Co., of 1871:— - - Indigo for Continent fine 350 to 362 rupees. - „ „ „ good 330 „ 345 „ - „ „ „ middling 310 „ 325 „ - American consuming fine 280 „ 300 „ - „ „ good 250 „ 275 „ - „ „ middling 200 „ 240 „ - „ „ low and ordinary 150 „ 170 „ - -At the present moment there is great depression in the trade in this -article. The last telegrams show a decline of price in the Indian -trade in this article of from fifty to seventy-five per cent from the -prices of last year; and the apprehension is even entertained that -indigo is going out of use, the dreaded competitors being the aniline -dyes, and particularly the Nicholson blue. We maybe presumptuous in -giving our opinion on the question, but we hazard the prediction that, -notwithstanding the temporary popularity of the cheap substitutes, a -reaction will take place in favor of that “wonderful and most valuable -production,” whose importance as a dye has been held in India for -thousands of years and Europe for two centuries, “greatly to exceed -any other.”[2] - - ------------------------------------------------------------- - [2] The “Dictionnaire Universel du Commerce,” &c., published in - 1861, contains an exhaustive article on the commerce in indigo, - by M. S. Beekrode. From the statements of this writer, it appears - that the consumption of indigo was estimated, in 1835, as follows:— - - Great Britain 1,214,380 kilograms (2,683,779) lbs. - France 912,915 „ (2,017,542) „ - United States 130,000 „ (277,300) „ - Other countries 2,435,473 „ (5,382,395) „ - --------- ----------- - Total 4,692,768 kilograms (10,362,016) lbs. - - The approximate consumption in 1859 is stated as follows:— - - Great Britain 800,000 kilograms (1,768,000) lbs. - France 800,000 „ (1,768,000) „ - United States 400,000 „ ( 884,000) „ - Russia 860,000 „ (1,900,600) „ - The Zollverein 1,250,000 „ (2,762,500) „ - Switzerland 150,000 „ ( 331,500) „ - Austria 400,000 „ ( 884,000) „ - Other countries 300,000 „ ( 663,000) „ - --------- ----------- - Total 4,960,000 kilograms(10,961,600) lbs. - - The average production in 1859 is estimated as follows:— - - Bengal, Madras, &c. 3,500,000 kilograms (7,735,000) lbs. - Java 550,000 „ (1,215,500) „ - Central America 300,000 „ ( 663,000) „ - Other sources 100,000 „ ( 221,000) „ - --------- ----------- - Total 4,450,000 kilograms (9,834,500) lbs. - - As the maximum annual consumption in 1859 is set down at - 5,000,000 kilograms, the author concludes that the average - production at that time did not surpass the requirements of the - dyers of the whole world. - ------------------------------------------------------------- - - -FORMER PRODUCTION IN THE CAROLINAS. - -As pertinent to the commercial branch of our subject, we must briefly -notice the remarkable facts of the sudden growth and equally sudden -and extraordinary extinction of the production of indigo in the -Carolinas. Indigo was for many years the second great staple of South -Carolina. So highly was this staple estimated that the historian of -the State declares that “it proved more really beneficial to Carolina -than the mines of Mexico or Peru are or ever have been to Old or New -Spain.” Its introduction was the happy result of a woman’s culture and -energy. In the early part of the last century, the indigo plant had -been extensively cultivated in the West India Islands, which then -furnished the chief supply of Europe. The governor of Antigua, George -Lucas, whose home plantation was at Wappoo in Carolina, having -observed the fondness of his daughter, Miss Eliza Lucas, afterwards -the mother of General Charles Cotesworth Pinckney, for the culture of -plants, was in the habit of sending to her tropical seeds to be sowed -on his plantation at Wappoo. Among others, he sent her some seeds of -the indigo plant cultivated in the West Indies. She planted them for -two years; but the seeds failed to germinate, or were killed by the -frost. On the third year’s trial, in 1741 or 1742, she was successful. -Governor Lucas, on hearing that the plants had ripened and produced -seed, sent from Montserrat a person skilled in making indigo. Vats -were built on Wappoo Creek, and there the first American indigo was -manufactured. The attempts of the expert to conceal his processes were -defeated by the vigilance of Miss Lucas. The process of manufacture -was made known. Seeds from the Wappoo plantation were freely -distributed and successfully planted; and the culture of indigo became -common. In 1747, a considerable quantity of indigo was sent to -England, which induced the merchants trading with Carolina to petition -parliament for a bounty on Carolina indigo. In 1748, an act of -parliament was passed granting a bounty of sixpence per pound on -indigo raised on British-American plantations and imported directly to -Britain from its place of growth. This act stimulated the planters of -Carolina to double vigor in the production of this new material for -export. “Many of them,” says Dr. Ramsay, “doubled their capital every -three or four years by planting indigo.” In the year 1754, the export -of indigo from the province amounted to 216,924 lbs., and in the years -1772 and 1773 the export had risen to 1,107,661 lbs. The production -was greatly checked by the war of the Revolution. Near the close of -the century the large importations from India lowered the price, so as -to make the planting unprofitable. In the mean time, the culture of -cotton had sprung up under the protective tariff of 1789. The grounds -suitable for indigo planting were equally fitted for cotton, and were -for the most planted with the new staple. It is curious to observe how -the former was displaced by the latter staple. The export of indigo -from Charleston in 1797 was 96,121 lbs.: in 1800, it fell to 3,400 -lbs. During the same years, the exports of cotton rose from one -million to six and a half million pounds. The production of American -indigo appears to have revived from time to time up to 1829. A writer -of that period in Silliman’s Journal of Science estimates—although it -would seem on doubtful authority—the production of indigo in the -United States at 20,000 lbs. The price of the American article had -fallen, owing to the great quantity of extractive which it contained, -to fifty cents per pound, while the Bengal indigo was worth $1.15 per -pound. We have no data as to its production at the present time, but -infer, from the fact that no reference has been made to this product -in the Government Agricultural Reports for many years past, that the -production, if any, is too unimportant to be noticed. - - -INDUSTRIAL APPLICATION OF INDIGO. - -All the applications of indigo require that the material should first -be reduced to an impalpable powder. It is better to grind it with -water, to prevent the loss of material in the form of powder, although -the dry pulverization is necessary when the indigo is to be used for -the manufacture of the sulphate. To facilitate the grinding the -material into a paste, it should be previously soaked in hot water -from one to three hours. The grinding on a small scale may be done by -a very simple apparatus. This is a hemispherical vessel of copper or -cast-iron, eighteen inches in diameter, furnished at the edge with two -handles. The workman, sitting astride a bench, places the vessel -before him, in which he places three heavy cast-iron balls, the indigo -which has been softened, and a sufficient quantity of water. Holding -the basin by the handles, he gives it a circular oscillatory movement, -in such a manner that the balls, following this movement, crush the -indigo which surrounds them; after which the contents are poured into -another vessel, water is added, and the material is stirred. The -portions incompletely ground are made to reunite themselves at the -bottom by means of regular blows with a hammer on the rim of the -vessel. The upper liquid is decanted, and the deposit is submitted to -a new manipulation in the basin. - -In large establishments the grinding is done by machinery. An -apparatus highly recommended, consists of two circular plates of -cast-iron, arranged horizontally and slightly separated, one from the -other, which are rapidly rotated by power, in inverse, directions. The -interior surfaces of these disks are provided with deep grooves -radiating in a curved line from the centre to the circumference, and -diminishing in depth in the same direction. The indigo which has been -previously softened enters between the two plates by an opening in the -centre of the upper one, and escapes in a thin paste by the -circumference. - -The application of indigo to the coloring of textile fabrics requires -the complete dissolving of the substance, for which the mechanical -division is only a preliminary. There are only two known means of -dissolving this substance: 1. By reduction; 2. By the action of -concentrated sulphuric acid. The first means allows indigotine to be -regenerated; and, when the dyeing is completed, it is pure indigotine -which adheres to the colored fibre. By the second means, or dissolving -by sulphuric acid, the coloring material enters into a new -combination, from which it can never be separated: it becomes a new -substance, endowed with new and special properties. - -_The fixing of Indigotine by means of Reduction_.—In this method the -operator avails himself of one of the most remarkable qualities of -indigotine: this is the facility with which this body takes up -hydrogen, and becomes transformed into a colorless substance, which is -soluble in favor of alkaline or alkaline-earthy bases, and is -susceptible of reproducing indigotine by simple oxidation in contact -with air. This hydrogenized substance is called white indigo. Blue -indigo, or indigotine, is insoluble except by concentrated sulphuric -acid; and this insolubility gives it its superiority to all other blue -dyes. Not being soluble, it cannot, as blue indigo, attach itself to -the material to be dyed; but in the soluble form of white indigo it -can perfectly penetrate the fibre. If by any means of oxidation we can -transform the white indigo into blue indigotine, the latter becomes -insoluble, and is imprisoned in the pores of the fibre. This is, -briefly, the whole theory of the use of indigo in dyeing or printing, -although the reaction may be applied in different ways to the coloring -of fibres, such as— - -1. The indigo is dissolved by means of an alkaline reduction in a vat, -and the fibre is immersed in the bath. This is the common blue vat. - -2. The solution prepared beforehand is painted by a hair pencil and -printed by a stamp or roller upon only certain parts of the tissues. -This is the pencil blue. - -3. The white indigo is precipitated under the form of a paste, in -combination with a metallic oxide having strong reducing power, such -as hydrated protoxide of tin, which prevents the too rapid reoxidation -of the indigotine. The thickened paste is printed, and the tissue is -placed in an alkaline bath (lime or soda), which, displacing the oxide -of tin, forms a soluble combination of white indigo. The latter can -then penetrate the fibre, and afterwards become fixed by reoxidation. -This is the printer’s solid blue. - -4. The finely ground, but not dissolved indigo, is placed upon the -tissue in such conditions that it can be dissolved and reduced in -place. This done, the fixing of the indigotine is effected by -oxidation. This is the method for China blue or _bleu faïence_. - -Without dwelling upon the details of these methods, we hasten to a -consideration of the most important of all the applications of indigo:— - - -DYEING BY THE INDIGO VAT. - -_The Copperas Vat_.—For dyeing cotton, the method of reduction found -by experience to be the most convenient and practical is founded upon -the action of the hydrate of the protoxide of iron in the presence of -lime. The hydrated protoxide of iron is obtained from sulphate of iron -(green vitriol, or copperas) with freshly burned lime. Certain -precautions should be observed in the use of these materials. The -copperas used for the preparation of these vats should be free from -sulphate of copper, because the oxide of copper which would be formed -in the vats rapidly oxidizes the reduced indigo, and causes its -precipitation in the bath. The copperas ought not to contain red oxide -of iron, nor sulphate of alumina. The coppery or oxidized vitriol may -be purified by boiling the solution with pieces of iron, which -precipitates the iron and neutralizes the oxide. The lime ought to be -pure, containing no magnesia; when slacked lime has been exposed to -the air, even for a short time, it absorbs carbonic acid, and becomes -converted into chalk. The lime, therefore, should always be newly -slacked. The ingredients, then, of a copperas vat are water, pure or -purified green vitriol, indigo ground into a homogeneous impalpable -paste, and pure and freshly slacked lime. The proportions used in -different establishments are exceedingly variable. Those which answer -for a laboratory vat, or a small vat used for precipitating the white -indigo immediately for printing, are: indigo, one part; sulphate of -iron, two parts; slacked lime, three parts. These proportions are not -enough for the large vats used in dyeing pieces. In them it is -necessary to make the quantities of lime and sulphate of iron larger -than the theory of the vat requires. The excess of lime and hydrate of -iron serve the purpose, whenever the vat is stirred, to repair the -losses of indigo caused by its oxidation from contact with the air. -Schutzenberger gives the proportions generally used by the dyers of -France, as follows:— - - Indigo 1 part. - Crystallized sulphate of iron 3 „ - Freshly slacked lime 3 „ - -Others, he says, use more lime than copperas, as in the following -proportion:— - - Indigo 2 parts. - Sulphate of iron 5.5 „ - Quicklime 6.5 „ - -M. de Kæppelin, who is especially familiar with the cotton dyeing in -Mulhouse, describes the ordinary vats for cotton dyeing as bound with -iron, and placed on the level of the ground. They hold from 3,000 to -4,000 litres (1,055 gallons) of liquid. In preparing them the dyer -fills them about three-quarters full of water, and pours in a milk of -lime, prepared with 45 kilograms (100 lbs.) of freshly slacked lime; a -fine liquid paste having been previously made from 15 kilograms (33 -lbs.) ground in water. This is added to the lime in the vat by -portions, the liquid in the vat being stirred up by a rake after each -portion of the indigo paste has been added. The indigo becomes -dissolved in about twenty-four hours, when the vat can be used. After -describing the manner in which the frame, or _champignon_, containing -the goods to be dyed is arranged and immersed in the vat, this author -continues: “It will be understood that the vat is composed according -to the degree of intensity of the color which is sought to be -obtained, and that hues more or less deep may be obtained by means of -more or fewer repeated immersions of the fabric to be dyed. After each -immersion the _champignon_ is lifted out of the vat, and the fabrics -are left to _ungreen_ themselves by contact with the air. (It must be -observed that, although soluble indigo is called white, because it is -without color when carefully prepared in the laboratory, the goods, -when first taken from the ordinary vat, are of a green color.) Exposed -to the air, the soluble indigo is precipitated in the state of blue -indigo upon the fibres of the tissue. This oxidation, or -_dehydryzation_, may be hastened by plunging the tissue into a vat -containing a solution, very much diluted with water, chloride of lime, -bichromate of potash, or sulphuric acid. The first two act as -oxidizing agents; the last facilitates the restoring of the blue -indigo by depriving it of the lime which is in excess in the solution -of indigo which the tissue has imbibed from the vat.” - -He adds further: “To facilitate the formation of blue indigo in the -interior of the fabrics, the stuff to be dyed may be previously -impregnated by a saline solution, which has the property of -precipitating the white indigo from the alkaline solution, and of -fixing itself more rapidly upon the tissue. Oxide of copper and oxide -of manganese possess these properties in a high degree, and are used -in many establishments to hasten the dyeing process, and produce an -economy in raw materials. The pieces of cloth are placed in a solution -of sulphate of copper, in the proportion of 15 to 20 grams to the -litre (2.11 pints), and lightly thickened with starch. The fabrics, -thus impregnated by a kind of mordant, before receiving the blue dye -are first passed through a weak bath of milk of lime, which fixes the -oxide of copper upon the tissue. The blues thus obtained are more -intense, and have a peculiar lustre. This process is used in Austria -and Germany, where cotton fabrics are printed on both sides of the -tissue.” - -Coming to the English authorities, Dr. Grace Calvert, in his recent -lectures before the Society of Arts, speaking of the cold vat for -dyeing cotton, says: “The oldest, and still most generally employed -method of preparing cold vats, consists of putting into a vat -containing about 2000 gallons of water 60 lbs. of indigo, very finely -powdered, 180 lbs. of slacked lime, and 120 lbs. of sulphate of -protoxide of iron, or green vitriol (free from any trace of copper -salt), the two latter substances being added from time to time. The -greater part of the lime used unites with the sulphuric acid of the -iron salt, to produce sulphate of lime or gypsum; and the liberated -protoxide of iron removes the oxygen from the indigo, becoming -converted into saline oxide, whilst the reduced indigo dissolves in -the excess of lime employed.” - -He adds the following facts, which may be of practical value:— - -“Messrs. R. Schloesser & Co., of Manchester, have introduced within -the last year or two a marked improvement, in the preparation of cold -vats, which removes the great objections of the bulky precipitate of -sulphate of lime, the formation of an oxide of iron, and the loss of -indigo by its combination with the oxide of iron. The bath remaining -much more fluid, the pieces are less apt to be spotted, and a better -class of work is produced. To carry out their process, they add to the -ordinary 2,000 gallon vat 20 lbs. of ground indigo, 30 lbs. of iron -borings, 30 lbs. of _their remarkable powdered zinc_, and 35 lbs. of -quicklime; the whole is stirred up from time to time, for twenty-four -hours, when it is ready for use. If the bath is not considered -sufficiently strong, a little more lime and zinc are introduced. The -chemical theory of the process is, that the zinc, under the influence -of the lime, decomposes the water, combining with its oxygen, and the -hydrogen thus liberated removes oxygen from the indigo which then -dissolves in the lime.” - -An excellent description of the processes employed at Manchester, -England, in preparing and working the copperas, or cold vat, is given -in Ure’s “Dictionary of Manufactures.” “The ingredients necessary for -setting the vat are copperas, newly slacked quicklime, and water. -Various proportions of these ingredients are employed, as, for -instance: 1 part by weight of indigo (dry), 3 parts of copperas, and 4 -of lime; or, 1 of indigo, 2¹⁄₂₃ of copperas, and 3 of lime; or, 8 of -indigo, 14 of copperas, and 20 of lime; or, 1 of indigo, ¾ of -copperas, and 20 of lime; or 1 of indigo, 4 of copperas, and 1 of -lime. The sulphate of iron should be as free as possible, from red -oxide of iron, as well as sulphate of copper, which reoxidize the -reduced indigo-blue. The vat, having been filled with water to near -the top, the materials are introduced, and the whole, after being well -stirred several times, is left to stand for about twelve hours. The -chemical action which takes place is very simple. The protoxide of -iron, which is set at liberty by the lime, reduces the indigo-blue; -and the indigo, which is then dissolved by the excess of lime, forming -a solution, which, on being examined in a glass, appears perfectly -transparent and of a pure yellow color, and becomes covered, whenever -it comes in contact with the air, with a copper-colored pellicle of -regenerated indigo-blue. The sediment at the bottom of the vat -consists of sulphate of lime, peroxide of iron, and the insoluble -impurities of the indigo, such as indigo-brown in combination with -lime, as well as sand, clay, &c. If an excess of lime is present, a -little reduced indigo-blue will also be found in the sediment in -combination with lime. The dyeing process itself is very simple. -The vat having been allowed to settle, the goods are plunged into the -clear liquor, and, after being moved about in it for some time, are -taken out, allowed to drain, and exposed to the action of the -atmosphere. While in the liquid, the fabric attracts a portion of the -reduced indigo-blue. On now removing it from the liquid, it appears -green, but soon becomes blue on exposure to the air, in consequence of -the oxidation of the reduced indigo-blue. On again plunging it into -the vat, the deoxidizing action of the vat does not again remove the -indigo-blue which has been deposited within and around the vegetable -or animal fibre, but, on the contrary, a fresh portion of the reduced -indigo-blue is attracted, which, on removal from the liquid, is again -oxidized like the first, and the color thus becomes a shade darker. By -repeating this process several times the requisite depth of color is -attained. This effect cannot, in any case, be produced by one -immersion in the vat, however strong it may be. The beauty of the -color is increased by finally passing the goods through diluted -sulphuric or muriatic acid, which removes the adhering lime and oxide -of iron. After being used for some time, the vat should be refreshed -or fed with copperas and lime, upon which occasion the sediment must -first be stirred up, and then allowed to settle again, so as to leave -the liquor clear. The indigo-blue, however, is in course of time -gradually removed, and by degrees the vat becomes capable of dyeing -only pale shades of blue. When the color produced by it is only very -faint, it is no longer worth while using it, and the contents are then -thrown away. In dyeing cotton with indigo, it seems to be essential -that the reduced indigo-blue should be in contact with lime. If potash -or soda are used in its place, it is impossible to obtain dark shades -of blue.” - - -FERMENTING VATS FOR WOOL DYEING. - -The application of indigo-blue to wool and woollen tissues is always -made by means of vats, which have special names; as, the pastel or -woad vat, the urine vat, German vat, molasses vat, &c. The reduction -or _hydrogenation_ of the indigo-blue is the result of a peculiar -fermentation, which is developed within an alkaline liquor by means of -nitrogenized substances and bodies rich in sugar or hydrocarbonized -substances. It is known that in these conditions, especially where the -temperature is slightly raised, the sugar is converted into butyric -acid, and at the same time carbonic acid and hydrogen are set free. We -find here the source of the nascent hydrogen which fixes itself upon -the indigo-blue, and transforms it into white indigo, which is soluble -in the alkalies of the vat. It has recently been observed that the -butyric fermentation proceeds from the development of minute -infusoria. These animalculæ live without any supply of oxygen, and, in -fact, are killed in its presence. They therefore live at their ease in -the vat of reduced indigo, where no oxygen is permitted to enter. - -The ingredients most usually employed for furnishing the -hydrocarbonaceous substances for fermentation are bran and ground -madder, although molasses is sometimes used. The nitrogenized material -is found in the woad or pastel, which is often added in very large -proportions to the fermenting vats. It is observed by the chemists who -have studied this subject most carefully, that the preparation of -vats, founded upon the principle of fermentation, does not repose upon -principles so sure and constant as those of the copperas vat, and that -many unforeseen accidents interpose to disturb the work of an -inexperienced dyer. The phenomena in fermentations are often complex. -It is admitted that in these phenomena theory has not said its last -word, and that empiricism is often more fortunate than science. In -conducting the operations of the warm fermenting vat, the conceit of -the practical dyer, so often remarked upon, is not without foundation. -By practical experience and the traditions of his art he has acquired -a knowledge of the almost insensible modification in conditions which -can change or arrest the chemical reaction. It is the knowledge of the -workman, a knowledge almost instinctive, which can never be -communicated to the books, and which is most respected by those most -profoundly informed in theory. - -_The Woad or Pastel Vat_.—In former times woad, already referred to, -was the only material known to the dyers of Europe for producing the -blue color of indigo. For dyeing wool, the use of woad, now abandoned -wholly in cotton dyeing, has been retained to the present day, -generally for the purpose of exciting fermentation, and without regard -to its effect in imparting color to the material to be dyed; for the -woad grown in England, and used in the dye-houses of that country, -contains no trace of coloring matter. The woad, or pastel, grown in -the warmer districts of France contains about two per cent of -indigotine, which is regarded in that country as an important addition -to the coloring material, especially for improving the tone of the -color. Various substitutes, such as rhubarb leaves, turnip and carrot -tops, and weld, have been tried, but without advantage, with the -exception, perhaps, of weld, which is still used by some dyers. Some -chemists regard the use of woad as the remnant of a prejudice; but the -better opinion is, that this material possesses peculiar -fermentiscible qualities, whose exact action science has yet to resolve. - -According to Schutzenberger, the most recent and highest French -authority, the dimensions of the pastel vat are about 6½ feet in -diameter, by 9 in depth. 100 kilograms (221 lbs.) of pastel, in balls, -is placed in the vat, which is then filled with boiling water. To this -is added 10 kilograms (22 lbs.) of madder, 3 to 4 kilograms (about 6½ -to 8¾ lbs.) of bran, and 4 kilograms of quicklime, which has been -slacked, and in the form of a _bouilli_. Sometimes weld is also added. -After three hours of rest, the vat is well raked, and the operation is -repeated every three hours. There is gradually developed a -characteristic ammoniacal vapor, and a blue scum, with veins of deeper -blue, forms on the surface; and the liquid, when agitated in the air, -rapidly becomes blue. These symptoms indicate the dissolution of the -indigotine of the woad; then there is added 10 kilograms (22 lbs.) of -indigo which has been previously ground in water, and the vat is -stirred. If the fermentation appears to be proceeding too actively, -which is recognized by the disengagement of gases, it is checked by -the addition of a proper dose of lime. On the other hand, the -fermentation is made more active by increasing the dose of bran. The -first dyes are not so good as those subsequently obtained, as the woad -absorbs from the bath certain brown or yellow materials, kept in -solution, and furnished as well by the pastel and madder as by the -indigo itself. 100 kilograms of wool require from 8 to 12 kilograms of -indigo. The vat is kept up by successive additions of indigo and lime, -made in the evening. - -Another kind of pastel vat, prepared much like the last, receives an -addition of a dose of potash. M. de Kæppelin describes it as the one -at present in general use in France. Into a vat containing from 3,000 -to 4,000 litres (791 to 1,055 gallons) there is placed 75 kilograms -(166 lbs.) of pastel in loaves, or which has undergone a kind of -fermentation; or, what is preferable, 80 to 100 kilograms (176 to 221 -lbs.) of pastel or woad gathered without fermentation, and 10 -kilograms (22 lbs.) of indigo, ground to a paste with water. This -mixture is well stirred, and there is added 4 kilograms (about 9 lbs.) -of Avignon madder, and the same quantity of carbonate of potash. After -the vat has been well raked there is added 2 kilograms (4½ lbs.) of -slacked lime, and some pails of bran. The vat is well covered, either -with a wooden lid, or woollen cloths. The fermentation is allowed to -proceed, and after five or six hours the vat is uncovered and raked -with much care for half an hour. This operation is repeated every -three hours, until it is recognized that the indigo is well dissolved. -In this case the bath ought to be of a beautiful yellow color, and be -covered with a light blue irised film, veined with yellow at the least -movement given to the liquid. If the fermentation proceeds too -rapidly, a little lime is added to moderate it. - -For keeping up a vat like this, and to obviate the different -inconveniences to which it is subject, the dyer sometimes adds lime, -or sugar, and carbonate of ammonia, sometimes madder, or bran, or even -tartar-lees. These last additions are made to saturate the excess of -lime which the vat contains. In this case the yellow veins and the -beautiful blue scum which cover the surface disappear, or become pale; -a piquant odor is disengaged, and the liquor becomes blackish. When -lime or sugar are added, it is for the purpose of retarding the -fermentation of the woad. Sugar might even entirely take the place of -pastel for effecting the reduction of the indigo, and many -establishments in France are commencing to use it for this purpose. A -good vat, well supplied with successive additions of indigo, pastel, -bran, and madder, in proportions necessary to effect and prolong the -fermentation necessary for the dissolution of the indigo, may be kept -up many years. - -Schutzenberger observes that the vats of fermentation are subject to -certain maladies, the two most frequent of which are due, one to an -excess, and the other to an insufficient quantity of lime. “In the -first case, the liquid takes a tint more and more free of color, loses -its _fleurée_ (surface scum) and odor; the fermentation is then -arrested by the precipitation of the active matters. This -inconvenience is remedied, if seen in time, by adding sulphate of -iron, which eliminates the too great excess of lime. In the second, -the fermentation becomes too active, passes into a putrid -fermentation, and the liquid assumes a reddish tint; a fabric dyed -with indigo in this state becomes very soon discolored. The sole means -of safety is to heat the bath up to 90° and to add lime. If this does -not accomplish the purpose of arresting the putrefaction the vat is -lost.” - -The following account of the method of dyeing woollen goods with -indigo by means of the woad vat is given by Dr. Ure, as that carried -on in Yorkshire, the great centre of the woollen manufacture of England. - -“The dye-vats employed are circular, having a diameter of six feet six -inches, and depth of seven feet, and are made of cast-iron -five-eighths of an inch in thickness. They are surrounded by -brickwork, a space of three inches in width being left between the -brickwork and the iron, for the purpose of admitting steam, by means -of which the vats are heated. The interior surface of the brickwork is -well cemented. In setting a vat the following materials are used: 5 -cwt. of woad, 30 lbs. of indigo, 56 lbs. of bran, 7 lbs. of madder, 10 -quarts of lime. The woad supplied to the Yorkshire dyers is grown and -prepared in Lincolnshire. It is in the form of a thick, brownish -yellow paste, having a strong ammoniacal smell. The indigo is ground -with water in the usual manner. The madder acts in promoting -fermentation, but it also serves to give a reddish tinge to the color. -The lime is prepared by putting quicklime into a basket, then dipping -it in water for an instant, lifting it out again, and then passing it -through a sieve, by which means it is reduced to a fine powder, called -by the dyers _ware_. The vat is first filled with water, which is -heated to 140° F., after which the materials are put in, and the whole -is well stirred until the woad is dissolved or diffused, and it is -then left to stand undisturbed overnight; at six o’clock the next -morning the liquor is again stirred up, and five quarts more of lime -are added; at ten o’clock five pints of lime are again thrown in, and -at twelve o’clock the heat is raised to 120° F., which temperature -must be kept up until three o’clock, when another quart of lime is -introduced. The vat is now ready for dyeing. When the process of -fermentation is proceeding in a regular manner, the liquid, though -muddy from insoluble vegetable matter in suspension, is of a yellow or -olive yellow color; its surface is covered with a blue froth or -copper-colored pellicle, and it exhales a peculiar ammoniacal odor; at -the bottom of the vat there is a mass of undissolved, matter of a -dirty yellow color. If there is an excess of lime present, the liquor -has a dark green color, and is covered with a grayish film, and, when -agitated, the bubbles which are formed agglomerate on the surface, and -are not easily broken. Cloth dyed in a liquid of this kind loses its -color on being washed. This state of the vat is remedied by the -addition of bran, and is of no serious consequence. When, on the other -hand, there is a deficiency of lime, or, in other words, when the -fermentation is too active, the liquor acquires first a drab, then a -clay-like color; when agitated, the bubbles which form on its surface -burst easily, and when stirred up from the bottom with a rake it -effervesces slightly, or _frits_, as the dyers say. If the -fermentation be not checked at this stage, putrefaction soon sets in, -the liquid begins to exhale a fetid odor, and when stirred evolves -large quantities of gas, which burns with a blue flame on the -application of a light. The indigo is now totally destroyed, and the -contents of the vat may be thrown away. No further addition of woad is -required after the introduction of the quantity taken in first setting -the vat, the fermentation being kept up by adding daily about four -pounds of bran with one quart or three quarts of lime. Indigo is also -added daily for about three or four months. The vat is then used for -the purpose of dyeing light shades, until the indigo contained in it -is quite exhausted, and its contents are then thrown away.” - -This author adds: “Woollen cloth, before being dyed, is boiled in -water for one hour, then passed immediately under cold water. If it be -suffered to lie in heaps after being boiled it undergoes some change, -which renders it afterwards incapable of taking up color in the vat. -In dyeing, the cloth is placed on a net-work of rope attached to an -iron ring, which is suspended by four iron chains to a depth of about -three feet beneath the surface of the liquor. The cloth is stirred -about in the liquor by means of hooks for about twenty or thirty -minutes. It is then taken out and well wrung. It now appears green, -but, on being unfolded and exposed to the air, rapidly becomes blue. -When the vat has an excess of lime the cloth has a dark green color -when taken out. It is then passed through hot water, and dipped again -if a darker shade is required.” - -_The Indian Vat_.—This presents much analogy to the woad vat, as the -fermentation of vegetable matters effects the transformation of the -indigo-blue. According to Dr. Calvert, the Indian vat, probably so -called from its origin in the East, is taking the place in England of -the old woad vat for dyeing wool and woollens. He describes its -preparation as follows: 8 lbs. of powdered indigo is added to a bath -containing 3½ lbs. of bran, 3½ lbs. of madder, and 12 lbs. of potash, -which is maintained for several hours at a temperature of 200° F. It -is then allowed to cool to 100° F., when fermentation ensues. After -about forty-eight hours the indigo is rendered soluble, being reduced -by the decomposition of the sugar and other products contained in the -bran and the madder root during the process of fermentation. The -distinguishing feature of this vat is the use of _potash_. The Indian -or potash vats are spoken of by the best authorities as more easy to -manage than the woad vat. They are less subject to accidents, and -yield their coloring material more readily to the fibre, while three -times as much wool can be dyed in the same time. On the other hand, -they do not last so long, and require to be renewed at the end of -twenty-five or thirty days. Besides, the fibres dyed in the potash vat -have a darker shade than those dyed in the woad vat, owing to the -large quantity of the coloring matter of the madder dissolved by the -potash, which becomes fixed on the stuff with the indigo-blue. - -_The Urine Vat_, but little used except for domestic dyeing, is -founded upon the same principles as the other fermenting vats. This -excretion, when putrefied, contains at the same time the nitrogenized -principles which work as ferments and the alkali in the form of -ammonia necessary for dissolving the indigo. - -According to Dr. Calvert, improvements have been made of late years in -the fermenting indigo vats by which the expense of madder is avoided. -They are now prepared by adding to water, at a temperature of 200° F., -2 buckets of bran, 26 lbs. of soda crystals, 12 lbs. of indigo, and 5 -lbs. of slacked lime. After five hours the bath is allowed to cool to -100° F., when fermentation ensues, and the indigo is dissolved in the -alkali. This is, in fact, the German vat, soda taking the place of the -potash, and the only fermenting material consisting of bran. - -_The German Vat_ is largely used by the dyers in the north of France, -and is considered as more advantageous than the Indian vat, because -the employment of soda is more economical than that of potash, while -the vat can be maintained as long as two years. The vats used by them -are prepared as follows: The water is heated to a temperature of 95°, -and receives 20 pails of bran, 11 kilograms (about 24 lbs.) of -crystals of carbonate of soda, 5.5 kilograms (11 lbs.) of indigo, and -4½ lbs. of slacked lime. After twelve hours, the temperature having -been kept at 40° or 50°, fermentation commences, the liquid becomes of -a greenish blue color, and disengages bubbles of gas. Indigo, soda, -and lime are put in from time to time in the proportions above -indicated, and also from six to eight pounds of molasses. At the end -of the third day the vat is fit for use. - -M. de Kæppelin, writing in. 1864, informs us that the reduction of -indigo by means of molasses, is at present largely employed in the -great establishments for dyeing woollen cloth at Sedan, Louviers, and -Elbœuf. - -The vat used is of very large dimensions, and from twenty-two to -twenty-six pounds of indigo are dissolved in it; an equal weight of -molasses is used, and three or four times the same weight of potash -made caustic by a proportionate addition of lime. - -The space reserved for this subject in our present paper will not -permit us to enter upon a description of the processes used in the -American dye-houses. This, as well as the applications of indigo in -printing, and the uses of sulphate of indigo, must be deferred to -another number. - -Let us, in concluding the first part of our paper, at the risk of -repetition, bring out in bolder relief a statement which presents the -philosophy of all the various processes of the indigo vat, and at the -same time, a conclusive argument for the use of this material, in -preference to all cheaper substitutes. Indigo cannot enter into a -fibre until it is dissolved. It cannot be dissolved so long as it is -in a blue state. When reduced by any of the processes above described -to the white state, it is easily dissolved, and can enter the pores of -the fibre. Upon exposure to the oxygen of the air it takes up an -equivalent of oxygen; it returns to the blue state, and, being then -insoluble, it cannot be washed away from the fabric, and being -saturated with oxygen it cannot be changed by air or light. This -theory of the application of indigo involves a lesson to -manufacturers, dealers, and consumers, especially of woollen fabrics. -The theory, as well as experience, dating back to the dawn of the -textile arts in the East, establishes that this material is -incalculably superior to any other, in permanence at least, for -imparting to woollen fibre a blue color, or as a foundation for most -of the darker colors. By far the largest proportion of all cloths are -of dark colors,—blue, black, green, brown, gray, or mixed,—and can -advantageously receive in all or a portion of the fibre constituting -them a direct dye or bottom for other dyes from indigo. It may be -safely stated that, as a whole, no cloths in the world are -manufactured from such good wool as those produced in the United -States. We might expect that the shoddy goods of Yorkshire should be -further falsified by fugacious dyes; but is it not a shame that our -admirable wool should be deprived of half its value by parsimony in -dyeing? The slightest shortcomings in dyeing are revealed in wear. The -writer cannot forbear referring to an illustration directly before his -eyes. He is wearing a garment, reduced now to the retired service of -an office coat, made of an admirable cheviot cloth of American -manufacture. The cloth originally was selected not only for its -excellent texture, but as an illustration of philosophical principles -applied in the formation of color. The tissue was made by weaving -three yarns of distinct colors,—blue, yellow, and red. Either of those -hues alone would have been glaring and conspicuous, but, by the law of -color, the combination of blue, red, and yellow makes black, and the -new cloth at a distance had the effect of a dark mixture. Upon -exposure to ordinary wear, the yellow and red have retained their -pristine hues; the blue, not being indigo dyed, has faded; and the -original dark mixture, although sound in fabric, has become of a -yellowish brown. The extra expense of a permanent dyeing material -forms so small a proportion of the whole cost of a finished garment, -that it ought not to be generally spared. The reform cannot be made by -the manufacturers; it must be made by the dealers, and especially by -that class of producers which has risen in our day into such great -importance,—the manufacturers of ready-made clothing. If they would -demand of the manufacturers, and furnish to their customers cloths -more permanently dyed, it would be another step in the direction to -which these establishments are tending,—the supply of the chief -portion of the woollen clothing of the people. The manufacturers would -gladly aid them; for it is the growing sentiment of American -manufacturers that all their productions should be, in the proverbial -phrase adopted from the dye-house, as expressing the highest -excellence,—_true blue_. - - -BIBLIOGRAPHY. - -Citations of authorities having been but partially made in the -preceding article, the writer, for the purpose of giving his sources -of information, and for the convenience of those who wish to pursue -the subject further, appends a list of the more important works which -he has consulted:— - -Schutzenberger’s Traité des Matières Colorantes, t. ii. (the most -recent and best modern authority); Bancroft’s Philosophy of -Permanent Colors, vol. i.; Edinburgh Encyclopædia; Berzelius, -Traité de Chimie, t. vi; Chevrueil, Leçons de Chimie Appliquée à -Teinture, t. iii.; Dumas, Chimie Appliquée aux Arts, t. viii; -Wurtz, Dictionnaire de Chimie, 1872, art. Indigo; Indigo et son -Emploi, par De Kæppelin; Annales du Génie Civil, 1864, t. iii.; -Lectures of Dr. Grace Calvert, Chemical News, Aug. 9 and 23, 1872; -O’Neill’s Dictionary of Dyeing and Printing; Napier’s Chemistry -Adapted to Dyeing; Muspratt’s Chemistry Applied to the Arts, -articles Indigo and Dyeing; Ure’s Dictionary of Manufactures, ed. -of 1860; Proceedings of Royal Society, vol. xvi.; Proceedings of -Literary and Philosophic Society of Manchester, vol. iv.; McCulloch’s -Dictionary of Commerce, ed. 1869; Dictionnaire Universel du -Commerce, &c., ed. 1861; _South Carolina Production_.—Ramsay’s -History; Drayton’s South Carolina; Silliman’s Journal, vol. xviii. -A more complete bibliography is given in Schutzenberger’s work. - - -PART II. - -PART II. - -We entered upon the subject of indigo, which we have treated at some -length in our last issue, as much in the interest of the people as of -manufacturers, for we were deeply impressed with the conviction that -no improvement in our manufacturing processes would confer more -benefit upon the masses than imparting stability of color to the -clothing of the people. When one has a deep conviction upon a subject, -upon which others have equal opportunities for judging, he may be sure -that he is not alone in his impressions. He is moved by one of those -waves of thought which, operating simultaneously upon many minds, -gives that uniformity to public opinion at which we so often wonder. -We are gratified to find, from responses to our last article, that we -are not alone in our conviction of the importance of reviving “true -blue” dyes. The head of a mercantile house, the extent of whose -_clientèle_ in mills both of wool and cotton is hardly surpassed, has -assured us that we have not overstated the reform in dyeing which we -have advocated. He had long shared in our convictions. Pointing to the -throng of men in the crowded street, where we were conversing, he -remarked that there was hardly a man in the crowd whose clothing would -not have been improved by indigo dye. “The failure to use indigo -dyes,” he emphatically said, “costs the laboring people of this -country millions of dollars every year. The fault is not to be charged -to our own manufacturers alone; for the blue coat which I wear, and -which I bought in Paris, annoys me by the crocking caused by its -aniline dye.” In one very large mill of which he is director as well -as selling agent, he is putting his principles in practice. All the -heavy blue cloths intended for popular consumption are faithfully -dyed, and each bears a stamp, “Warranted indigo dyed.” The ready-made -clothing establishments which largely consume these goods have already -found their advantage in purchasing them, and a similar stamp is -attached to each article made from this cloth. - -Some of our most celebrated cotton fabrics have won and still retain -their reputation by the use of indigo dyes. The ginghams are a signal -illustration. The blue check is formed by weaving cotton yarns dyed -blue in the cold indigo vat with undyed yarns. These goods can be -washed indefinitely without change. - -Another illustration is the famous A.B.A. Amoskeag tickings, an -article of such excellence that the question of the right to use -trade-mark A.B.A. gave rise to the leading American case in this -branch of law.[3] A prominent feature in these goods was and still is -the permanence of the dye in the blue stripe, produced by the cold -indigo vat. Still another illustration is the blue and white “shirting -stripe” first made by Mr. Samuel Batchelder, at the Hamilton Mills, -now so generally adopted for sailors’ shirts. The indigo dye enables -the color to resist the roughest possible usage. - - ------------------------------------------------------------- - [3] See the case stated at length in our article on Trade-marks, - Bulletin, vol. i. p. 102. - ------------------------------------------------------------- - -To recur to the application of indigo dyeing to wool and woollens. We -have been unable, although we have written more than fifty letters of -inquiry upon the subject, to learn of any peculiarity or improvements -in the American processes of wool dyeing with indigo.[4] Our dyers are -for the most part foreigners. For this reason, or because the art of -indigo dyeing has long since reached perfection in the best -establishments abroad, they rigidly pursue the old European methods. -The best dyers regard the successful management of the warm fermenting -vats for wool as the highest test of their art. We have already spoken -of the complicity of the phenomena in fermentations. Practical dyers -endow the fermenting vat with a sort of personality. “An indigo vat,” -says one to us, “is more like a sick man than any thing in the world: -you have to watch it as you would a sick patient, and give it physic -or ferments to stir up the system and purify it.” [5] The diagnosis of -a sick vat requires that sort of instinctive knowledge which -experience gives to the practised physician. The impatience of our -young Americans will not permit them to serve the long apprenticeship -necessary to acquire the proper experience. The artisans not -thoroughly trained will naturally prefer the dyes and processes -introduced by modern science, which require but little skill in their -application. It is a curious fact that the influence of the national -government has been largely instrumental in preserving the old system -of indigo dyeing. Thanks to the Quartermaster-General’s Bureau, or the -man of science, General Meigs, who presides over it, indigo dyed -cloths have been persistently insisted upon for the army. The late war -gave a new impulse to indigo dyeing. A skilled dyer, whom we have -consulted, was constantly employed in Connecticut, on a tour of -professional inspection of a dozen or more different establishments -making army goods. No doctor, he says, ever found in hospital practice -more complications of disease than he found in the ailing vats. Among -other difficulties there was a deficiency of imported woads, although -the cultivation of excellent woad immediately sprung up in -Connecticut. In the mean time carrot and rhubarb tops were used as -substitutes for the fermenting material of the woad. Carrot-tops grown -expressly for that purpose brought as high as twenty-five cents per -pound. Since the war the requisitions for indigo dyed woollen goods -have not relaxed, and the art is not likely to be lost. - - ------------------------------------------------------------- - [4] A reply by Mr. D. R. Whitney, an extensive indigo importer, - to a letter of inquiry, enables us to correct some errors in our - former article, under the head of “commerce in indigo.” The value - of export from India in 1862–63, stated in dollars, through a - typographical error, should have been pounds sterling; thus, - instead of $2,126,814, read £2,126,814. It is stated in our first - article that the telegrams show a decline of price of indigo in - the Indian trade of from 50 to 75 per cent; “per cent” should - read “rupees,” which would make a decline of from 25 to 30 per - cent. The reason for the decline, as stated by Mr. Whitney, is - the unusually large crop of this year. The average crop of indigo - in Bengal is about 100,000 maunds. The crop of this year is - 135,000 maunds, about 30 to 35 per cent above the average. - - According to Mr. Whitney, the consumption of Bengal indigo in the - United States was 2,458 cases of 270 lbs. to a case on an - average, in 1871; and in 1872, 1,802 cases. Guatemala indigo, - 3,132 serroons in 1871, and 2,578 serroons in 1872. - - [5] See notes on “sickness” of vats in Appendix. - ------------------------------------------------------------- - -With the real difficulties which attend the process, it is hard for -indigo dyeing to sustain itself in the face of cheap substitutes of -easy application, such as the Nicholson blue. It is exceedingly -difficult to piece dye with indigo and preserve a uniform hue upon the -cloth. Hence indigo dyes are generally given in the wool. The wool -absorbing the foreign material of the dye is more difficult to work in -the operations of carding and spining. In other words, a finer and -costlier wool is required. A great _desideratum_ therefore is a means -of piece dyeing with indigo so as to preserve a perfect uniformity of -hue throughout the piece. This, we are happy to say, has been recently -successfully accomplished by one of the largest and most faithful of -our cloth-making establishments. It would be premature, before the -patents are secured for this invention, to explain the ingenious and -expensive apparatus devised for this purpose, which constitutes in -fact a battery of vats so arranged that the operation may be -continuous. The experiments authorize the statement that bottom dyes -of indigo, so desirable for a great variety of colors, can be applied -with no other additional cost than that of the dyeing material. When -this establishment, as it proposes, stamps upon the cards which -designate goods, already so admirable in material and texture, -“Warranted indigo dyed,” we shall regard it as an era in the American -card-wool manufacture. - -The old European woad vat process is that used in all our -establishments. Mr. Henderson of the Washington Mills, whose -experience as a practical dyer of wool is exceptionally large, informs -us that he has found no work so instructive upon this process as -Napier’s “Chemistry of Dyeing” (published by Henry Carey Baird, of -Philadelphia, 1869). Napier’s description of the process is extracted -from Dumas’s “Lectures on Dyeing.” The appreciation expressed by so -competent a judge induces us to reprint Dumas’s description in an -appendix to this article. - -That we may give at least a general view of the whole subject, we will -proceed to consider indigo in some relations not yet adverted to. - -In Part I. of our notes we have treated only of the application of -this substance in dyeing by means of reduction through the indigo vat. -Indigo may be applied by means of reduction in the printing of -fabrics, as well as in dyeing them. A true scientific arrangement -would compel us next in order to consider this other application of -indigo by means of reduction. But the more natural and practical order -is to pursue the subject of dyeing, and to consider next the -applications of the derivatives from indigo in dyeing proper. - - -SULPHURIC DERIVATIVES,—SAXON BLUE, &C. - -The powerful action of sulphuric acid upon indigo, and the bright and -lively blue color thereby produced, had been observed by chemists long -ago; but no person appears to have applied this color upon cloth, -until it was done about the year 1740, by Counsellor Barth, at -Grossenhein, in Saxony. The vividness of the dye, and the facility -with which it was applied, brought it into great vogue under the name -of Saxon blue, from its origin. Its popularity in former times is -evinced by the words of the old song, “The Blue Bells of Scotland:”— - - “In what clothes, in what clothes is your Highland laddie clad? - His bonnet’s of the Saxon blue, his waistcoat of the plaid.”[6] - - ------------------------------------------------------------- - [6] First sung by Mrs. Jordan, about the year 1799. - ------------------------------------------------------------- - -The Saxon blue consists simply of a solution of indigo, the Guatemala -blue indigo being preferred, in sulphuric acid suitably diluted with -water. The result of this reaction is not a single chemical substance, -but two acids giving different tints, one called _sulpho-purpuric_ -acid or _phenicine_, and the other _sulpho-indigotic_ acid; the first -giving to wool a reddish-violet color, and the other a pure blue. A -third compound has been indicated by Berzelius, the nature of which -has not been determined. Whether one or the other of the two named -acids, or the two combined, shall be produced by the reaction between -the sulphuric acid and the indigo, depends upon the duration of the -contact, the temperature of the mixture, and the nature and proportion -of the acid used. - -Persoz gives the following general receipt:— - - “1 part by weight of indigo, finely rubbed. - 1 „ „ „ „ Nordhaussen acid. - 1 „ „ „ „ ordinary sulphuric acid. -Leave for forty-eight hours, then heat until a drop turned into -water will dissolve without producing a precipitate. Leave to cool, -and dilute with water till the strength is brought to 18 Beaumé.” - -Napier says that he has found the following method of preparing -sulphate of indigo, in quantities for use, very satisfactory: “The -indigo is reduced to an impalpable powder, and completely dried by -placing it on a sand bath or flue for some hours at a temperature of -about 150° F. For each pound of indigo six pounds of highly -concentrated sulphuric acid are put into a large jar, or earthen pot, -furnished with a cover. This is kept in as dry a place as possible, -and the indigo is added gradually in small quantities. The vessel is -kept closely covered, and care taken that the heat of the solution -does not exceed 212°F. When the indigo is all added, the vessel is -placed in such a situation that the heat may be kept up at about -150°F., and allowed to stand, stirring occasionally, for forty-eight -hours. These precautions being attended to, we have uniformly found -that any failure occurring was clearly traceable to the impurity of -the indigo or weakness of the acid used.” - -The processes for producing and separating the two acids derived from -the combination of sulphur and indigo are minutely given by Berzelius, -in vol. i. of his “Traité de Chemie,” who states this curious fact -illustrative of the peculiar affinities of wool with certain dyeing -substances. Wool or flannel thoroughly scoured, when immersed in the -blue solution of indigo with sulphuric acid, acts as a base: it -combines gradually with the acid blue, and becomes itself colored of a -deep blue. When saturated with color, it is withdrawn. Fresh wool is -introduced until the bath yields no more color. If sublimed or -perfectly pure indigo is used, there remains in the bath nothing but -free sulphuric acid. The wool thus plays the part of a base with which -the blue acids combine. The dyed wool is afterwards washed and treated -in feeble alkaline bath (ammonia), which redissolves the blue. This -method of purifying the Saxon blue is still practised by French -manufacturers. - -The combination of indigo with sulphuric acid, sometimes improperly -called sulphate of indigo, is known by the dyers here and in England -under the name of _chemic_. The name of _chemic_ blue or green is also -given the dyes formed from the indigo extract hereafter spoken of. It -is largely used for making certain greens required in Scotch plaids. - -The old Saxon blue or simple solution of indigo with sulphuric acid is -now seldom prepared by the manufacturers themselves. It is now -generally prepared for them, and furnished commercially under the name -of _indigo extract_. The finer qualities used for fine dyeing and -printing are known under the name of _carmines_ of indigo, _neutral -extract_, _soluble indigo_, _ceruline_, &c. - -The production of indigo carmines, which are simply alkaline -sulphindigotates or sulpho-purpurates, is founded upon their -insolubility in a liquid charged with a salt. - -If, for example, we dissolve one part of indigo in four parts of -fuming acid, and dilute the liquid with sixty or eighty times its -weight of water, it will contain, besides the _sulphindigotic_ acid, -an excess of sulphuric acid. By adding one part of crystals of soda so -as to neutralize the bath, there will be formed not only -sulphindigotate of soda, but sulphate of soda: as the former is -insoluble in the saline liquid, the presence of the sulphate of soda -causes the precipitation of the sulphindigotate in deep blue -floccules. These are collected on woollen filters and washed to remove -the sulphate of soda and a green coloring material, probably a -modified chlorophyl, which the paste often contains, and which has the -singular property of fixing itself on silk, but not on wool. - -The carmines are divided according to their richness in indigo into -simple carmine (4.96 per cent of indigo, water 89, saline materials -57), double carmine (10.2 per cent indigo, water 85, salts 4–8), -triple carmine (12.4 per cent indigo water, 73.7, salts 13.9). A -species of solid carmine known as Boiley blue or purple is in high -repute in France. - -The carmines may be tested by dyeing a specimen of wool in an -acidulated bath to which cream of tartar has been added. The presence -of the green matter, so objectionable to silk-dyers who make much use -of these carmines, is detected by rubbing a small quantity of the -carmine on a piece of glazed paper, which, when the color dries, gives -a color varying from blue to a rich copper color: if any green -coloring matter is left, it shows itself by a green aureola around the -blue color. The method of applying the carmines in dyeing wool and -silk,—for they are not adapted to cotton fabrics,—as given by M. de -Kæppelin, is as follows:— - -The operation is conducted in small wooden vats, provided with -openings for manipulation, and pipes for inducting steam to heat the -baths to the proper temperature. It consists of two parts, that of -mordanting and dyeing. The former is thus conducted. - -For each kilogram of tissue which has been previously scoured and -bleached, there are provided 200 grammes of cream of tartar and 250 -grammes of alum. These are dissolved in the bath of water of the vat, -the temperature is raised to boiling heat, and the tissue is immersed -in the bath f of an hour while it is worked over through the opening -for manipulation. The pieces are then taken from the bath, to which is -added a solution of the carmine in water containing a quantity of -coloring matter proportionate to the intensity of the blue sought for. -The solution ought to be prepared with care and passed through a silk -sieve, so that the small insoluble grains which might have been left -through bad fabrication may be left on the sieve. After the pieces -have been manipulated in the colored bath, so as to exhaust the color -and obtain the required blue, they should be rapidly washed in running -water and dryed in the shade. Silk stuffs are dyed in the same way; -but the alum should be previously applied cold by means of a saturated -solution of alum, in which the stuffs should be immersed for an hour. - - -COLORS NOT FAST. - -In regard to all the combinations of indigo with sulphuric acid, -including the carmines, it must be observed that their application -does not constitute true indigo dyeing: the colors are not fast. It is -not pure indigotine which is fastened on the tissues as in the vat -dyeing, but another compound of indigo with the sulphur. Berzelius -observes that “the color of soluble indigo is fully as alterable and -fugacious as that of the colors extracted by the decoction of -vegetable materials. By a long exposure to the sun the indigo blue is -destroyed: it becomes green during evaporation, and changes its -nature.” The carmines as well as the sulphur acids are easily -decolorized by reducing agents, such as hydrogen and sulphuretted -hydrogen, although they gradually assume their original color when -exposed to the atmosphere. We are informed by some of the older -dealers that imported cloths and merino stuffs known as “Saxony” were -formerly largely sold in our shops, but that, notwithstanding their -attractiveness to purchasers, they were objectionable on account of -the instability of their color. - - -APPLICATION OF INDIGO IN PRINTING STUFFS. - -Our notes would be incomplete without some reference to the uses of -indigo in printing fabrics. In pursuing this branch, we are -embarrassed on the one hand by the consideration that the subject is -too technical for the general reader, and on the other by the -consciousness that it would be presumption in us to attempt to -instruct those skilled in the art. It may not, however, be without -benefit in producing a higher appreciation of science for the general -reader to observe how science comes in play, even in the printing of a -single color; while to the skilled reader our notes may possibly be of -value as a vehicle for conveying some receipts taken from works not -easily accessible. - - -PRINTING STUFFS OF WOOL AND SILK, AND STUFFS WITH COTTON WARPS. - -This branch of our subject is directly allied to the one last -considered, the application of the compounds of sulphur and indigo; -for indigo is applied to printing wool and silk principally in the -form of indigo carmines. These applications are less numerous than -they were formerly, since they have been replaced by Prussian blue, -and more recently by the aniline blues, which are now generally used. -When the carmines are used, it is for making sky blues, and they enter -into the composition of some greens and browns. The salts of alumina -and vegetable acids are used to fix the indigo carmine upon tissues of -wool and silk. Some receipts recommended by M. de Kæppelin, himself a -practical printer, are given in a note.[7] - - ------------------------------------------------------------- - [7] BLUE NO. 1. - Indigo carmine 400 grammes. - Alum 100 „ - Oxalic acid 150 „ - Boiling water 1¼ litre - Gum water prepared in proportion of - 1 kilogram to the litre 1¼ litre - - GREEN NO. 1. - Gum water as above 12 litres. - Cuba lac 12 „ - Alum 1 kilogram, 500 grammes. - Oxalic acid 2 „ - Indigo carmine 4 „ - - BOUILLON FOR THE GREENS AND BLUES. - Boiling water 12 litres. - Alum 600 grammes. - Oxalic acid 750 „ - Gum water 12 „ - - SKY BLUE FOR WOOLLEN STUFF WITH COTTON WARP. - - First solution.—Boiling water 4 litres. - Cyanuret of iron and potash 800 grammes. - Second solution.—Boiling water 2 „ - Tartaric acid 300 „ - - Third solution.—Cold water 3 „ - Sulphuric acid 300 „ - - Pour in the first solution, then the second and third, agitating the - color with a spatula after each new addition. - - The following mixture is afterwards applied to the stuff:— - - Gum water 12 litres. - Water 6 „ - Blue No. 1 for wool 3 „ - ------------------------------------------------------------- - -In printing tissues of wool with cotton warp, the carmines are not -used alone. They are combined in certain proportions with cyanites of -iron and potash, to obtain upon the cotton a blue color of equal -intensity with that produced by the carmines upon wool. It is also -necessary to previously mordant the fabrics by means of a solution of -oxide of tin or caustic soda which is precipitated on the fibres by -passing through a bath of water, to which sulphuric acid has been added. - - -APPLICATIONS OF INDIGO IN PRINTING COTTON FABRICS. - -Before entering upon methods used in large establishments, it may not -be without interest to observe the processes still used in Java for -printing calicoes, which the natives prefer to any imported from -Europe. In Java there are no factories, and the women in each family -make and dye or print all the cotton cloths required for their own -consumption. They apply by means of a brush or pencil, which they use -with great skill, to the cotton tissue which they wish to cover a thin -coating of wax mixed with a little resin, the wax being applied to all -the parts where the design, which has been first traced upon the -cloth, requires that the fabric should remain uncolored. They then -immerse the stuff several times in an indigo vat until they have -obtained the desired tint. The stuff is afterwards washed and dried -for a new application of the wax, carefully applied with a pencil as -before. The cloth is then immersed in a bath of a different color, -made with madder or catechu, but always of some dye which is perfectly -stable; and the operation is repeated according to the number of -colors desired. By these successive applications of wax and immersions -into different vats, they succeed in producing very complicated and -harmonious colors, while no European goods compare with them in -stability of dye. - -In the European, and our own manufacture, the blue bottoms upon -vegetable fibres, made by immersion in the indigo vat, are combined -with white impressions, or others variously colored, by two distinct -methods. Sometimes there is printed upon the cloth before dyeing in -the indigo vat a preparation called a reserve or resist, which -prevents the indigotine from being deposited in the places where it is -applied. Sometimes, on the contrary, the indigo, which has been -uniformly fixed upon the fabric, is destroyed in certain places marked -out by printing upon them certain chemical agents, called _discharges_. - -The _reserves_ are mechanical, resisting the penetration of the dye, -such as wax and pipe clay, or chemical. The last, through these acid -or oxidizing properties, cause the precipitation of the indigotine -before it has touched the fibre or penetrated into its pores. Such are -the salts of copper and bi-chlorate of mercury. Other bodies perform -the part both of mechanical and chemical reserves. The salts of zinc -or alumina, for instance, which are frequently used, produce at the -same time a deposit of indigo white and a gelatinous covering of -hydrated oxide of zinc or aluminium. The composition of a good reserve -is declared to be principally a question of good proportions of the -constituent parts, varying with the strength of the vat and the -intensity of the blue which is desired to be reserved. The first -condition is that it hardens immediately after immersion in the vat: -if it softens, on the contrary, it will cause the running of the -color. In other words, the acidity of the impression should be -proportionate to the strength and alkaline character of the vat. The -white reserve, that most generally used, is composed of pipe clay, -gum, verdigris, and sulphate of copper. The styles of work produced by -dipping with reserves are generally of a cheap and low class. The -system is clumsy and expensive, and is only tolerated because of the -want of a method of directly applying indigo, which will yield the -deepest shades. - -Certain styles, formerly in great vogue, called _Lapis_, and forming -one of the richest branches of the cotton-printing industry, are -founded upon the use of reserves; and in these styles, by very simple -means which we shall not attempt to describe, different colors -produced from madder, catechu, &c., are produced upon the fabric so -perfectly surrounded by blue that the eye cannot detect the slightest -want of continuity. This fabrication has the greatest perfection in -Russia. The imitation cashmere fabrics of cotton imported from that -country, formerly much in fashion for dressing-gowns, are specimens of -this fabrication. The great stability of the colors is a remarkable -feature of these goods. - -The system of resists or reserves possesses the inconveniences of not -producing impressions of great firmness, and of requiring very strong -vats. When the strength of the vat is partially exhausted, they may be -thrown aside. These inconveniences are obviated by the system of -discharges (_enlevages_). In this system the cloths are vat dyed of a -uniform blue. The strength of the vat is of less importance, and it -can be used until the indigo is quite exhausted. The means of -destroying the indigo which has been fixed upon the fibre are founded -on the use of active oxidizing agents, which transform the insoluble -indigotine into soluble isatine. The agent generally used is chromic -acid. As this acid cannot be incorporated with the thickening to be -printed, as the thickening would produce oxide of chrome, the cloth is -passed through a strong solution of chromate of potash, and dried in -the shade. The required pattern is then printed on the cloth with a -mixture whose principal elements are acids which are susceptible of -setting free the chromic acid on the tissue, which then acts upon the -indigo producing a white pattern. The acid generally employed for -freeing the chromic acid is oxalic acid, thickened with British gum, -dextrine, or starch, with the addition of pipe clay. To prevent -running, nitric, sulphuric, or tartaric acid are sometimes used.[8] - - ------------------------------------------------------------- - [8] Schutzenberger gives the following receipts:— - - PREPARATION FOR DISCHARGE. - - Water 2 litres. - Yellow chromate 500 grammes. - - WHITE DISCHARGE ON BLUE BOTTOM. - - Tartaric acid 3 kilograms. - Oxalic acid 250 grammes. - Burnt starch 4 kilograms. - Nitric acid 500 grammes. - Water 4 litres. - - De Kæppelin gives the following:— - - WHITE DISCHARGE ON BLUE. - - Water 2 litres. - Starch 1 kilogram, 800 grammes. - Oxalic acid 500 grammes. - Tartaric acid 250 grammes. - Sulphuric acid 375 grammes. - - The pieces, having been dyed blue, are then placed in a solution of - bichromate of potash in water, which is prepared in the ratio of 50 to - 60 grammes to the litre, according to the intensity of the blue. The - pieces thus prepared must be dried away from direct solar light or too - much heat. In fact, under the action of these agents, the bichromate - would be decomposed and the tissue altered. The pieces are often - rolled up to prevent this effect. After the pieces are printed, they - are passed into a vessel containing water and holding chalk in - suspension in sufficient quantity to give it a milky aspect. The - temperature of the bath is raised to 60° R. The excess of acid of the - color applied is saturated by the chalk, and the excess of bichromate - of potash with which the tissue is impregnated is dissolved in the - bath. The pieces are afterwards washed and passed through slightly - soapy water. - ------------------------------------------------------------- - -By the method of discharges the white designs upon blue are brought -out with a distinctness which it is impossible to obtain by resists, -while the most delicate work of the graver can be exactly reproduced -upon the tissue. - - -APPLICATION OF INDIGOTINE BY PRINTING. - -The first step in the art of printing indigotine upon calicoes was the -application of what is called pencil blue. Instead of immersing the -fabrics in an indigo vat, the indigo white formed in a very strong -indigo vat was thickened and applied locally to certain places on the -cloth. The preparation was painted upon the cloth by means of pencils -made of willow sticks, the ends of which were broomed up into a kind -of brush. The style was hence called pencil blue. The methods now used -to apply white indigo locally are of two kinds. The china blue -process, and the solid blue process, sometimes called fast or -precipitated blue. The china blue process derives its name from the -resemblance of its color to the blue on the old china ware. It has -great depth of tint, and permanency. It is scarcely used now, except -for certain articles requiring great depth of color, such as certain -furniture goods, and by the Germans and Swiss for the manufacture of -calicoes for exportation to India. - -We do not venture to condense the descriptions at our hand of the -processes for applying the china blue and the solid blue, and -translate those furnished by chemists of high authority. After the -method indicated by Darwin in his recent works, we present them in -smaller type, with the perhaps unnecessary suggestion that they may be -passed over by the general reader. - -_China blue_.—The theory of this printing blue, says Schutzenberger, -is very simple. The indigo, reduced to an impalpable powder and -thickened, is printed by a plate or roller. After drying, the tissue -seems dyed blue, more or less deep, according to the proportion of -coloring material used; but it is only a blue of application, which -can be removed with the thickening, by the slightest washing. The -object is now to reduce and redissolve the indigotine in place to -enable it to penetrate the fibre at the end of a consecutive -oxidization, and without producing a running of the color or altering -the purity and distinctness of the contours of the design. I owe to M. -Ed. Schwartz some valuable hints upon the fabrication of this style, -which is also described with much care and details in the treatise on -printing by M. Persoz. - -The reduction of the indigo is obtained by alternate passages of the -printed tissue into vats containing,—the first, quicklime slacked; the -second, sulphate of iron; the third, soda. The operation is terminated -by a passage through a bath of sulphuric acid, which removes the oxide -of iron and precipitates the indigo white by hastening its oxidation. - -The success depends upon the composition of the color printed, and -above all upon the strength of the vats of immersion and the duration -of the treatment. - -The operator uses six vats,—for instance, two lime vats, provided each -with 12 kilograms of lime; a copperas vat at 70 Beaumé; a caustic soda -vat marking 140 Beaumé; a sulphuric acid vat with 500 grammes of acid -(_par mesure d’eau_); and finally a vat of pure water. - -The receipts for printing are:— - -1. THE BLUE PREPARATION. - - Ground indigo 4 kilograms. - Acetate of iron 10 litres. - Sulphate of iron 1 kilogram. - Water 10 litres. - Gum Senegal 6 kilograms. - -Pass through a sieve; leave some time at rest, and stir whenever used. -Caraccas indigo is preferred because it can be broken into a finer -powder and gives a finer paste. - -2. COLORS FOR ROLLER PRINTING NOS. 1, 2, 3, 4. - -The blue preparation above 1, 1, 3, 4. -Acetate of iron containing 700 grammes of gum per litre 2, 1½, ½, ½. -Gum water at 600 grammes per litre 16, 2½, ½, ½. - -These proportions can be varied according to the tint desired. - -The piece is treated a quarter of an hour in the first lime vat by -giving it a light movement from above to below; it is left a quarter -of an hour in repose in the sulphate of lime vat; a quarter of an hour -in the second lime vat; a quarter of an hour in the copperas vat; five -minutes in the caustic soda; half an hour in the sulphuric acid, and -then thoroughly rinsed. - -To each lime vat there is given 2 kilograms of lime per piece of -cloth. To the vitriol vat there is added 50 kilograms of sulphate of -iron for each dozen pieces. The soda vat is renewed after 5 pieces by -the addition of 12 kilograms of salt of soda, which has first been -made caustic. The acid vat receives 25 kilograms of acid after 5 -pieces, and ought to be renewed whenever it becomes saline. The other -vats must be cleared out whenever the deposit becomes too great for -success. - -M. Ed. Schwartz recommends as important conditions, (1) the perfect -causticity of the tissue, and an average strength of 140 Beaumé; (2) -the neutrality of the sulphate of lime vat. For this end old iron -should be boiled in it. - -After leaving the sulphuric acid vat the pieces are rinsed in the -water vat, then in river water, and afterwards should be soaked in a -sulphuric acid bath at 40 Beaumé, for the purpose of dissolving the -last traces of the peroxide of iron adhering to the fibre. The fabric -is then washed in water and finally passed through a soapy water at -40° R. - -_Solid or precipitated blue, Schutzenberger’s receipt_.—The process -consists in printing indigo white precipitated in a vat, in a thick -paste to dissolve it on the tissue by a passage through an alkaline -bath (lime or soda), and of reprecipitating it by oxidizing it as soon -as it has entered the fibre. - -It is then the china blue process, minus the reduction which is made -before printing, and consequently minus the sulphate of iron vat. - -Indigo white is too alterable to be printed with success, so it is -generally precipitated in combination with a stannic hydrate (hydrate -of a salt of tin), which gives it body and preserves it from a too -rapid oxidation. - -The stannic indigotate in paste, or as it is generally called -precipitate of indigo, is prepared by turning into the clear portion -of a strong copperas vat an acid solution of protochlorate of tin, and -filtering it upon woollen filters,—as much as possible away from the -air. It would be better to prepare a strong tin vat by heating a -mixture of indigo, caustic soda, and protochlorate of tin, and to -precipitate by chlorohydric acid.[9] - - ------------------------------------------------------------- - [9] Mr. T. P. Shepard gives in his valuable “Receipts for Calico - Printing,” published in 1872, the following:— - - NO. 52. INDIGO PRECIPITATE FOR FAST BLUE AND GREEN. - - 10 pounds quicklime, slacked with - 6½ gallons water; then - 2 pounds ground indigo finely rubbed in water are stirred in; then add - 6 pounds copperas dissolved in 5 gallons of water; then add - 5 gallons hot water and - 15 gallons cold water. - - Stir well from time to time, until the liquid has assumed a yellow - color and deep blue veins or streaks appear on its surface. When this - moment arrives, draw off the clear liquor, and precipitate every ten - quarts of it with - - ½ pound tin crystals, dissolved in ½ pound muriatic acid. - - To the remainder of the mixture of lime and indigo, 15 gallons of - water may be added, and the whole stirred; and when settled, the - indigo may be precipitated from the clear liquor as before. This - operation may be repeated a second time before all the indigo is - exhausted. - - The indigo precipitate is to be collected on a muslin filter, and - well squeezed out. - ------------------------------------------------------------- - -The deposit is made into a paste with gum water; a salt of tin is -often added to prevent oxidation. It is important to prevent the -transformation of the indigo white into indigotine before printing. -This indigotine would not fix itself on the fabric. Moreover, after -printing, it is necessary to hasten the dissolution of the indigo -white to enable it to penetrate the fibre. It is sufficient for this -end to pass it through milk of lime. The stannic combination is -immediately destroyed; the colorable matter unites itself with the -lime, and the color passes into a pale gray with apple green. The -indigo white becomes momentarily soluble; but the presence of the -excess of lime and the thickening, as well as the attractive affinity -of the thickening, prevent any running. - -The piece on issuing from the lime water is placed in running water, -when reoxidation commences, which this time fixes the color. The piece -is finally passed through a sulphuric acid bath to absorb the lime, -and washed. - -By adding to the color a salt whose base precipitates in the milk of -lime and oxidizes in the running water, and replacing the simple acid -bath by an acid bath with yellow prussite, the intensity of the blue -is increased through the formation of Prussian blue. - -Although we have seen beautiful effects from the application of the -solid blue of indigo on prints at our Pacific Mills, the colors -produced by Prussian blue and aniline are so much more brilliant and -easy of application that the use of indigo in printing goods for -ordinary consumption is likely to decline rather than increase. It -will be otherwise if we should ever manufacture for the East India -markets. Here is a field still open for our manufacturers. Mr. Watson, -in his beautiful work on “The Costumes of the People of India,” -remarks that “British manufacturers have hitherto failed to appreciate -Oriental tastes and habits, and hence supply but an insignificant part -of the clothing of the two hundred million persons that form the -population of what is commonly spoken of as India.” The great defect, -he observes, is the want of stability of color in the cotton fabrics -introduced,—this stability being an imperative demand in the Oriental -markets. - -The applications of indigo to cotton fabric are altogether secondary, -in our mind, to its relations to the woollen manufacture. If we have -felt called upon to say a word in behalf of the most ancient and best -ally which the fibre of wool has ever had, it is because the vividness -of color of the new products of coal, and the fascination which the -application of the recent discoveries of science always possesses, is -threatening the eclipse of the more ancient sober and solid dyes. Let -the new colors have their place as auxiliaries, not as substitutes for -the ancient dyes. Let them serve to give a bloom[10] to goods, but let -the foundation be the good old dyes which the experience of ages has -proved to be the most unalterable by light and air. The recent -wonderful discovery of alizarine, or artificial madder, in coal tar -products, has led practical men to expect too much from science. The -opinion is quite prevalent among manufacturers that artificial -indigotine has already been obtained from the same source. And some -manufacturers are sanguine that the difficulties of indigo dyeing will -thus be resolved. It is not improbable—for what is impossible to -modern chemistry?—that this result will yet be partially obtained. But -we have looked over all the recent foreign chemical reviews, and -personally consulted some of our best chemists, and we can find no -authority for the prevailing opinion that artificial indigotine has -been produced. If the production of artificial indigotine should be -realized, the only benefit would be the possible cheapening of the -material. The difficulties of the indigo vat would still remain; for -we cannot too often repeat, that in the very difficulties of the -process, or in the insolubility of blue indigotine by ordinary agents, -consists the excellence of the dye. - - ------------------------------------------------------------- - [10] _Guernsey Blue_.—The darkest of the Nicholson Fast Blues. On a - bottom of barkwood, camwood, madder, or inferior _indigo_, produces - an indigo blue which will stand all the acid tests the same as - colors made from indigo. - - _Serge Blue_.—It will be found very serviceable to give bloom to - goods dyed with indigo, and by itself shows a very good indigo test - with nitric acid.—_Instructions for Working the Atlas Works Aniline - Dyes_. - ------------------------------------------------------------- - - -APPENDIX. - -DYEING WOOL IN THE WARM INDIGO VAT. - -[_Extract from Dumas’s Lectures on Dyeing_.] - -The value attached by practical wool-dyers to the following induces us -to publish it without condensation:— - -Indigo Blue.—We give a solid dye of indigo blue to wool by plunging it -into an alkaline solution of indigo white, and then exposing it to -contact with the air. The solution of indigo white is prepared in a -vessel usually from eight to nine feet in depth, and six to seven feet -in diameter. This size is very convenient for the requisite -manipulations, and presents a large volume of water, which, when once -heated, is capable of preserving a high temperature for a long time. -This vessel should be made of wood or copper. It always bears the name -of vat. These vats are covered with a wooden lid, divided into two or -three equal segments. Over this lid are spread some thick blankets. -Without this precaution the bath would come in contact with the -atmospheric air, a portion of the indigo would absorb oxygen and -become precipitated. There would also be a great waste of heat. - -A most necessary operation, and one which has to be frequently -repeated, consists in stirring up the deposit of vegetable and -coloring matter which is formed in the vat, and intimately mixing it -in the bath. For this purpose we employ a utensil called a _rake_, -which is formed of a strong square piece of wood, set on a long -handle. The workman takes hold of this with both hands, and, dipping -the flat surface into the deposit at the bottom of the vessel, he -quickly draws it up until it nearly reaches the surface, when, giving -it a gentle shake, he discharges the matter again through the liquor -of the bath. This manœuvre is repeated until the whole of the deposit -seems to be removed from the bottom of the vessel. Before the tissue -is dipped into the dye-bath, it should be soaked in a copper full of -tepid water; it is then to be hung up and beaten with sticks. In this -state it is plunged into the vat; it thus introduces less air into the -bath, while it is more uniformly penetrated by the indigo solution. -The cloth is now kept at a depth of from two to three feet below the -surface of the liquid, by means of an open bag or piece of network -fixed in the interior of an iron ring, which is suspended by cords, -and fixed to the outside of the vat by means of two small iron hooks; -the bag is thus drawn backwards and forwards without permitting it to -come in contact with the air. When this operation has been continued -for a sufficient length of time, the cloth is wrung and hung up to dry. - -Flock wool is also, for the purpose of dyeing, enclosed in a fine net, -which prevents the least particle from escaping, and which is fixed in -the bath in the same way as in the foregoing case. - -The many inconveniences attending the use of wooden baths, which -necessitate the pouring of the liquor into a copper for the purpose of -giving it the necessary degree of heat, have led to the general -employment of copper vessels. These are fixed in brickwork, which -extends half way up their surface, whilst a stove is so constructed at -this elevation that the flame shall play around their upper part. By -this means the bath is heated and kept at a favorable temperature -without the liquor being obliged to be removed. - -The potash vats are usually formed of conical-shaped coppers, -surrounded by a suitable furnace. These may be constructed with less -depth, inasmuch as there is less precipitation induced in the liquor. -By using steam for heating the vats, we might dispense with the -employment of copper vessels, and so return to those of wood. - -The vats employed for dyeing wool are known under the names of the -pastel vat, the woad vat, the potash vat the tartar-lee vat, and the -German vat. - -Pastel Vat.[11]—The first care of the dyer in preparing the vat should -be to furnish the bath with matters capable of combining with the -oxygen, whether directly or indirectly, and of giving hydrogen to the -indigo. We must, however, be careful to employ those substances only -which are incapable of imparting to the bath a color which might prove -injurious to the indigo. These advantages are found in the pastel, the -woad, and madder. This latter substance furnishes a violet tint when -brought into contact with an alkali, and by the addition of indigo it -yields a still deeper shade. - - ---------------------------------------------------------------------- - [11] The distinction between pastel and woad is not very clear. - Schutzenberger says: “Pastel, woad, and satis tinctoria is a _plant_ - of the family of the crucifera. It would seem, however, that the term - _pastel_ as used by the old French dyers is applied to the leaves of - the woad which have been fermented, formed into paste, and afterwards - into balls, and which contain much blue coloring matter. And the term - _woad_ as distinguished from _pastel_ is applied to the unfermented - plant.” - ---------------------------------------------------------------------- - -In preparing the Indian vat, we ordinarily employ one pound of fine -madder to two pounds of indigo. The madder is here especially useful, -by reason of the avidity of some of its principles for oxygen. - -The pastel vat, when prepared on a large scale, ordinarily contains -from 18 to 22 lbs. of indigo; 11 lbs. of madder would suffice for this -proportion, but we must also bear in mind the large quantity of water -which we have to charge with oxidizable matters. I have invariably -seen the best results from employing 22 lbs. to a vat of this size. -Bran is apt to excite the lactic fermentation in the bath, and should -therefore not be employed in too large a quantity; 7 to 9 lbs. will be -found amply sufficient. - -Weld, which is often used, is rich in oxidizable principles; it turns -sour, and passes into the putrid fermentation with facility. Some -dyers use it very freely; but ordinarily we employ in this bath an -equal quantity of it to that of the bran. Sometimes weld is not added -at all. - -In most dye-houses the pastel is pounded before introducing it into -the vat. Some practical men, however, maintain that this operation is -injurious, and that it interferes with its durability. This is an -opinion which deserves attention. The effect of the pastel, when -reduced to a coarse powder, is more uniform; but this state of -division must render its alterations more rapid. When the bath has -undergone the necessary ebullition, the pastel should be introduced -into the vat, the liquor decanted, and at the same time 7 or 8 lbs. of -lime added, so as to form an alkaline lye which shall hold the indigo -in solution. Having well stirred the vat, it should be set aside for -four hours, so that the little pellets shall have time to become -thoroughly soaked, both inside and out, and thus be prepared for -fermentation. Some think coverings are to be spread over the vat, so -as to preserve it from contact with the atmosphere. After this lapse -of time, it is to be again stirred. The bath at this moment presents -no decided character; it has the peculiar odor of the vegetables which -it holds in digestion; its color is of a yellowish-brown. - -Ordinarily, at the end of twenty-four hours, sometimes even after -fifteen or sixteen, the fermentative process is well marked. The odor -becomes ammoniacal, at the same time that it retains the peculiar -smell of the pastel. The bath, hitherto of a brown color, now assumes -a decided yellowish-red tint. A blue froth, which results from the -newly liberated indigo of the pastel, floats on the liquor as a thick -scum, being composed of small blue bubbles, which are closely -agglomerated together. A brilliant pellicle covers the bath, and -beneath we may perceive some blue or almost black veins, owing to the -indigo of the pastel which rises towards the surface. If the liquor be -now agitated with a switch, the small quantity of indigo which is -evolved floats to the top of the bath. On exposing a few drops of this -mixture to the air, the golden-yellow color quickly disappears, and is -replaced by the blue tint of the indigo. This phenomenon is due to the -absorption of the oxygen of the air by the indigogen from the pastel: -in this state we might even dye wool with it without any further -addition of indigo; but the colors which it furnishes are devoid of -brilliancy and vivacity of tone, at the same time that the bath -becomes quickly exhausted. - -The signs above described announce, in a most indubitable manner, that -fermentation is established, and that the vat has now the power of -furnishing to the indigo the hydrogen which is required to render it -soluble,—that contained in the pastel having been already taken up; -this, then, is the proper moment for adding the indigo, which should -be previously ground in a mill. - -We stated above that the liquor of the vat should be previously -charged with a certain quantity of lime; we also find in it ammonia -generated by the pastel; but a part of these alkalies become saturated -by the carbonic acid gas along with the proper acids of the madder and -of the weld, as well as by the lactic acid produced by the bran during -fermentation. The ordinary guide of the dyer is the odor, which, -according to circumstances; becomes more or less ammoniacal. The vat -is said to be either soft or harsh; if soft, a little more lime should -be added to it. The fresh vat is always soft; it exhales a feeble -ammoniacal odor accompanied with the peculiar smell of the pastel; we -must, therefore, add lime to it along with the indigo; we usually -employ from five to six pounds, and, after having stirred the vat, it -is to be covered over. The indigo, being incapable of solution except -by its combination with hydrogen, gives no sign of being dissolved -until it has remained a certain time in the bath. We may remark that -the hard indigoes, as those of Java, require at least eight or nine -hours, whilst those of Bengal do not need more than six hours, for -their solution. We should examine the vat again three hours after -adding the indigo. We ordinarily remark that the odor is by this time -weakened; we must now add a further quantity of lime, sometimes less, -but generally about equal in amount to the first portion; it is then -to be covered over again, and set aside for three hours. - -After this lapse of time, the bath will be found covered with an -abundant froth and a very marked copper-colored pellicle; the veins -which float upon its surface are larger and more marked than they were -previously; the liquor becomes of a deep yellowish-red color. On -dipping the rake into the bath, and allowing the liquid to run off at -the edge, its color, if viewed against the light, is of a strongly -marked emerald-green, which gradually disappears, in proportion as the -indigo absorbs oxygen, and leaves in its place a mere drop rendered -opaque by the blue color of the indigo. The odor of the vat at this -instant is strongly ammoniacal; we also find in it the peculiar scent -of the pastel. When we discover a marked character of this kind in the -newly formed vat, we may without fear plunge in the stuff intended to -be dyed; but the tints given during the first working of the vat are -never so brilliant as those subsequently formed; this is owing to the -yellow-coloring matters of the pastel, which, aided by the heat, -become fixed on the wool at the same time as the indigo, and thus give -to it a greenish tint. This accident is common both with the pastel -and the woad vats; it is, however, less marked in the latter. - -When the stuff or cloth has been immersed for an hour in the vat it -should be withdrawn; it would, in fact, be useless to leave it there -for a longer time, inasmuch as it could absorb no more of the coloring -principle. It is therefore to be taken from the bath and hung up to -dry, when the indigo, by attracting oxygen, will become insoluble and -acquire a blue color. Then we may replunge the stuff in the vat, and -the shade will immediately assume a deeper tint, owing to renewed -absorption of indigo by the wool. By repeating these operations, we -succeed in giving very deep shades. We must not, however, imagine that -the cloth seizes only on that portion of indigo contained in the -liquor required to soak it. Far from such being the case, experience -shows that, during its stay in the bath, it appropriates to itself, -within certain limits, a gradually increasing quantity of indigo. We -have here, then, an action of affinity, or perhaps a consequence of -porosity on the part of the wool itself. - -Woad Vat.—These vats are extensively employed at Louviers, and in the -manufactories of the north of France. The bath is prepared in the same -manner as in the foregoing case; the finely cut root is introduced -into the copper along with 2 lbs. of pounded indigo, 9 lbs. of madder, -and 15½ lbs. of slaked lime. The liquor is, after the necessary -ebullition, poured upon the woad. This substance contains but a very -small quantity of coloring principle; we must, therefore, add some -indigo when preparing the vat, so as to indicate the precise instant -when the mixture arrives at the point of fermentation so necessary for -imparting hydrogen to the coloring principle, and for rendering it -soluble. We must also use a larger quantity of lime, since the woad -contains no ammonia resulting from previous decomposition, such as we -find to be the case with the pastel of the south. When the vat is in a -suitable state of fermentation, a rusty color becomes manifest, in -addition to the signs already described in speaking of the pastel vat; -besides the ammoniacal odor, the bath always retains the peculiar -smell of the woad. The pounded indigo is now added, and we proceed, in -the manner already detailed, to reduce it to a state of solution fit -for dyeing. - -The vats prepared by means of pastel have greater durability than -those made with the woad; but it is thought that the colors given by -the latter are more brilliant than those obtained from the former dye. - -Modified Pastel Vat.—This vat is about 7 feet in depth, and 6½ feet in -diameter. It is made of copper, and heated by steam. The lid is -composed of three segments, each of which is formed of two planks, -about an inch thick, and strongly secured together by bolts. - -The beating is performed in the usual way, with sticks before the -first dipping, after having moistened the cloth in tepid water. This -operation is not subsequently repeated. - -This vat is prepared with 13 lbs. of indigo, 17½ lbs. of madder, 4½ -lbs. of bran, 9 lbs. of lime, and 4½ lbs. of potash. Having filled the -vat, we heat it to about 200° Fah., and, as soon as the water is -tepid, introduce 441 lbs. of pastel. The liquor becomes of a -yellowish-brown color; small bubbles appear upon its surface, -ordinarily at the end of four hours if the vat be heated by steam, but -not until after eight or twelve hours where heat is applied by the -common fire; in the latter case the mixture should be stirred every -three hours. When the liquor displays the signs of fermentation, we -add the above-mentioned ingredients, and cover the vat over; it is -then to be set aside, stirring it every three hours, or oftener if the -fermentative action be very rapid. Each time that it is stirred we are -to add from 2 to 4 lbs. of lime; if fermentation proceed quickly we -even use more, but in the contrary case less. After about eighteen -hours, we plunge into the vat three pieces of common cloth, measuring -from twenty to twenty-five ells in length each; when they have -received six or seven turns, they are to be taken out again. The -object of this is to remove the excess of lime from the bath. The vat -is then set aside for three hours, when it is to be stirred, and 13 -lbs. of indigo, with 2 lbs. of madder, added to it. We now again apply -heat to the mixture. - -If the vat contains a superabundance of lime, it will be unnecessary -to add more; otherwise we throw in a further quantity. During the -night it should be covered with a cloth, and a workman left to watch -it. It is usually stirred once before the morning; but if it be -deficient in lime, it will require this manipulation to be more -frequently repeated, and also fresh lime added to it. On the following -day the stirring should be continued every three hours, and so on for -the next thirty hours, taking care to heat the vat from time to time. -On the morning of the fourth day the dyeing may be commenced. - -The temperature should be maintained at a pretty uniform point; if it -be too hot, the blue takes a red reflection, by reason of the madder -contained in the liquid. A vat thus prepared will last three months; -we may even work it for double that period, but after the third month -it appears to lose some of its indigo. - -We maintain the power of the vat by introducing every night 2¼ lbs. of -madder. Some indigo is also added twice or three times a week. These -additions are made in the evening. After the former, the vat is left -at rest for forty-two hours; with the latter only for twenty-four, at -the same time observing the precautions already indicated. At the end -of three months, or sooner when we wish to stop the working of the -vat, we exhaust the indigo; for this purpose we continue to charge it -every night for the space of a month with madder, and dip into it -white cloths, or more particularly woollen tissues, which become more -or less loaded with the indigo. We must continue this plan until these -matters take up no further color. The dippings are to be performed -twice a day at first, but once only towards the termination. Many -dyers make use of this bath for preparing a new vat, but it is better -to throw this away and make it up afresh with common water. - -Indian Vat.—These vats are of more simple and of more ready -construction than the pastel or woad vats. We are to boil in water a -quantity of madder and of bran, proportioned to the weight of indigo -which we wish to employ. After two hours’ ebullition, we turn into -this bath some tartar-lees, which are also to be boiled for an hour -and a half or two hours, so as to charge the bath with whatever -soluble matter they may contain; after this ebullition the bath should -be allowed to cool, and the indigo, which has been previously ground, -is then to be introduced. Supposing that we wish to employ 21 lbs. of -indigo, the following would be the proportions used in preparing this -vat: 41 lbs. tartar-lees, 13 lbs. of madder, and 5 lbs. of bran. These -vats are usually mounted in coppers of a conical shape; a small fire -should be kept up around them, so as to maintain a moderate and -uniform heat. The indigo will usually be found dissolved at the end of -twenty-four hours, often even after twelve or fifteen hours. The -liquor has a reddish color in the new vats, and a green tint in those -which are in a working state. The frothy surface, as well as the -brilliant-colored pellicle, becomes manifested in this as in all other -preparations of a like kind. - -This species of vat has to be renewed much more frequently than the -woad and pastel vats, from the indigo being more difficult to dissolve -after a certain lapse of time. A moderate heat should be maintained in -all these vats. - -Potash Vat.—This species of vat is extensively employed at Elbœuf for -the dyeing of wool in the flock. It presents in all respects a perfect -analogy with the Indian vat; in fact, the action of the tartar-lee in -the latter preparation depends entirely on the carbonate of potash -which it contains. The ingredients used in the preparation of the -potash vat are bran, madder, and the subcarbonate of potash of commerce. - -We obtain the deep shades in this species of vat with greater celerity -than in all others, a fact which undoubtedly depends on the greater -power which potash has of dissolving indigo than is possessed by lime. -Experience proves that the potash vat has the advantage in point of -celerity of nearly a third; but this is balanced by the inconvenience -resulting from the darker shade, which we must attribute to the large -quantity of coloring matter of the madder dissolved by the alkaline -lee, and which becomes fixed on the stuff with the indigo. - -To render this vat in its most favorable state, the indigo should be -made to undergo a commencement of hydrogenation before turning it into -the mixture; for this purpose we prepare in a small copper a bath -analogous to that in the vat, to which the pounded indigo is added. -This bath is maintained for twenty-four hours at a moderate heat, -taking care to stir it from time to time. The indigo assumes a -yellowish color, becomes dissolved, and in this state is turned into -the vat; we thus avoid many delays and losses in its preparation, and -indeed it would be desirable if a similar plan were adopted with all -these compounds. - -German Vat.—This vat is of nearly similar dimensions to that used for -the woad, being three times the size of the potash vat. Its diameter -is about 6½ feet, and its depth 8½ feet. Having filled the copper with -water, we are to heat it to 200° Fah.; we then add 20 pailsful of -bran, 22 lbs. of carbonate of soda, 11 lbs. of indigo, and 54 pounds -of lime, thoroughly slaked, in powder. The mixture is to be well -stirred, and then set aside for two hours; the workman should -continually watch the progress of the fermentation, moderating it more -or less by means of lime or carbonate of soda, so as to render the vat -in a working state at the end of twelve, fifteen, or, at the most, -eighteen hours. The odor is the only criterion by which the workman is -enabled to judge of the good state of the vat, he must therefore -possess considerable tact and experience. - -In the process of dipping we introduce 84 lbs., 106 lbs., or even 130 -lbs. of wool, in a net bag, similar to that used in the woad vat, -taking care that the bag is not allowed to rest against the sides of -the copper. When the wool has sufficiently imbibed the color, we -remove the bag containing it, and allow it to drain for a short time -over the vessel. We operate in this way on two or three quantities in -succession; we then remove the vat, and set it aside for two hours; we -must be careful, from time to time, to replace the indigo absorbed by -the wool, as also to add fresh quantities of bran, lime, and -crystallized carbonate of soda, so as constantly to maintain the -fermentation at a suitable point. - -The German vat differs, then, from the potash vat by the fact that the -potash is replaced by crystallized carbonate of soda and caustic lime, -which latter substance also gives to the carbonate of soda a caustic -character. It presents a remarkable saving as compared to the potash -vat; hence the frequency of its employment; but it requires great -care, and is more difficult to manage. It also offers considerable -economy of labor; one man is amply sufficient for each vat. - -The army cloth is usually dyed by means of the pastel vat, which gives -the most advantageous results. We here make use of vats about 8½ feet -in depth, and 5 feet in diameter, into which we introduce from 361 -lbs. to 405 lbs of pastel or of woad, after previous maceration. The -vat is to be filled with boiling water, and we then add to the bath 22 -lbs. of madder, 17½ lbs. of weld, and 13 lbs. of bran. The mixture is -to maintained in a state of ebullition for about half an hour; we next -add a few pailsful of cold water, taking care, however, not to lower -the temperature beyond 130° Fah.; during the whole of this time a -workman, provided with a rake, keeps incessantly stirring the -materials of the bath. The vat is then accurately closed by means of a -wooden lid, and surrounded by blankets, so as to keep up the heat. It -is now put aside for six hours; after this time it is again stirred by -means of a rake, for the space of half an hour; and this operation -should be repeated every three hours until the surface of the bath -becomes marked with blue veins; we then add from six to eight pounds -of slaked lime. - -The color of the vat now borders on a blackish-blue. We immediately -add the indigo in a quantity proportioned to the shade which we wish -to obtain. The pastel in the foregoing mixture may last for several -months; but we must renew the indigo in proportion as it becomes -exhausted, at the same time adding both bran and madder. In general we -employ— - - 11 to 13 lbs. of good indigo for 100 lbs. of fine wool. - 9 to 11 lbs. of good indigo for 100 lbs. of common wool. - 9 to 11 lbs. of good indigo for 131 yards of cloth dyed in the piece. - -Management of the Vats.—A good condition of the vat is recognized by -the following characters: The tint of the bath is of a fine -golden-yellow, and its surface is covered with a bluish froth and a -copper-colored pellicle. On dipping the rake into the bath, there -escapes bubbles of air, which should burst very slowly; when they -vanish quickly, it becomes an indication that we must add more lime. -The paste which is found at the bottom of the vat, green at the moment -of its being drawn up, should become brown in .the air; if, however, -it remains green, this is a further sign that more lime is required. -Lastly, the vat should exhale the odor of indigo. We usually complete -the assurance of the vat being in a good state by plunging into it, -after two hours’ respite, a skein of wool, which, on being withdrawn -after the lapse of half an hour, should present a green color, but -change directly to blue. We then once more mix the materials of the -vat, and two hours after it may be considered ready for dyeing. - -These vats, like those already described, are provided with a large -wooden ring, the interior of which is armed with a kind of network, -for the purpose of preventing the objects which are intended to be -dyed coming in contact with the materials at the bottom of the vat; -we, moreover, take the precaution of enclosing the wool or cloth in -bags. These tissues, when plunged into the bath, should remain there -for a longer or shorter time, according to the shade which we wish to -obtain; one dipping, however, will never suffice for this object; -usually we leave in the stuff for half an hour only; it is then to be -taken from the bath, wrung, and exposed to the air. This operation is -repeated until we have succeeded in procuring the desired shade; we -ordinarily suffer three hours to elapse between each dipping. The heat -of the vat should never be allowed to fall below 130° Fah. After each -operation the bath must be well stirred, and fresh lime added; -generally speaking, a pound a day will suffice. We re-establish the -indigo about every second day. When once this vat is well mounted, and -we are careful to examine its working, we may dye from two to four -batches a day with it. - -When the stuffs have acquired the desired shade, they are first to be -washed in common water, and then in a very weak solution of -hydrochloric acid (about one part in a thousand); after this they are -again rinsed in pure water. - -The Indian vat is much more easily managed than the foregoing; it -presents less danger of failure, from the fact that it is quickly -exhausted, and also from the fermentative process, which is so -difficult to govern in the pastel vat; this vat not having time to -change in character. It is prepared by first introducing an equal -quantity of madder and of bran, and a triple quantity of potash; this -is to be gradually heated until it reaches a temperature of 167° Fah., -and we then add to it the indigo, thoroughly agitating the matters for -half an hour. The vat is maintained at a temperature of 86° to 100° -Fah., by keeping it closely covered, and at the same time the mixture -is to be stirred occasionally at intervals of twelve hours. It should -by this time present a beautiful green shade, the liquor being -surmounted by a copper-colored pellicle and a purplish froth. We may -now commence the dyeing, following the same course as with the pastel -vat; but the stirrings being here repeated much more frequently than -with the other mixture, we can dye a larger quantity of wool within a -given time. When the vat ceases to give a brilliant blue, we must -altogether renew it; if it be merely weakened, we add to it a small -quantity of freshly prepared liquor containing a few pounds of potash, -and a little less bran and madder. In giving the dark and the clear -sky blues, we must be careful to employ a quantity of indigo -proportioned to the color which we wish to obtain, or, better still, -we may use the previously exhausted vat for the dark blue. - -When exposed to the influence of the putrid fermentation, indigo is -decomposed and loses its color. If rendered soluble, it obeys the -impulse communicated to the azotized matters with which it is brought -into contact, although, if macerated in pure water at the ordinary -temperature, it is itself decomposed with great difficulty. - -The pastel and the woad are very prone to the putrid fermentation, by -reason of the large quantity of azotized matters which they contain, -as do all the cruciferæ; they require therefore considerable care in -their employment. - -When a vat is mounted, if the fermentation be allowed to continue -unchecked, after the appearance of the blue froth and the other signs -already indicated, the liquor will acquire a yellow color similar to -that of beer; the froth will become white; it will give out a stale -smell and lose its ammoniacal odor; after a few days it will turn -whitish, and exhale a smell at first similar to that of putrefied -animal substances; then it will acquire the odor of rotten eggs, and -set free sulphuretted hydrogen. The lime in the pastel and the woad -vats, and the tartar-lee and potash in the other mixtures, are used -for the purpose of preventing these accidents. - -Besides the oxygenated compound, which is formed by the combination of -oxygen with the extractive matters of the plants held in digestion, -there is a production of carbonic acid which saturates the alkaline -lee, and forms a carbonate of lime in the pastel vat. We find this -attached to the sides of the vat in such quantity that the inside of -these vessels becomes incrusted with it to a considerable depth. It is -this product which dyers call the tartar of the vat; it effervesces -with acids, and gives on analysis carbonic acid, lime, and a few -particles of indigo. In the potash vat the solubility of the carbonate -of potash prevents its deposition; but it is very probable that we -have even here a formation of some carbonated products, perhaps in -part formed at the expense of the carbonic acid of the air. - -The soluble extractive principle being the only matter which remains -in solution in the bath with the indigo, the lime, &c., we have formed -deposits which, varying both in their volume and in the greater or -less facility with which they are precipitated during the various -periods of fermentation, lead to a more or less considerable waste of -time. If we plunge a piece of woollen tissue into a vat which has been -recently stirred, it will acquire a dark color, and will be found -covered with brown stains which are with difficulty removed. When the -woad or paste vat has been stirred, it need be left two or three hours -only before plunging in the stuff, at least during the early months of -its working, inasmuch as the pastel, being but slightly divided and -attenuated, is readily precipitated; but when, by reason of its -extreme division, in consequence of repeated operations, it is thrown -down with less facility, the dipping should not be performed oftener -than three times in the day. - -The Indian vat requires less time than the others; we may even dye -with it an hour after stirring the mixture. The potash, being soluble, -forms no precipitate; while the ligneous fibre of the madder and the -pellicles of the bran become deposited with great facility. We can -also dip with these vats much oftener than with those made by pastel -or woad. - - -SICKNESS OF THE WARM VAT FOR DYEING WOOL, AND ITS REMEDIES. - -We have to thank that excellent practical magazine, “The American -Chemist,” for the following notes on the sicknesses of the warm vat, -by F. W. Kugler, translated from Reimann’s Färberzeintung:— - -In the wool indigo vat, among the principal “sicknesses” is the -blackening of the vat, or “sharpening.” This arises from the presence -of too much lime. When “sharpened,” the liquor, instead of having a -waxy yellow color with a dense blue film on its surface, has no film; -while the liquor is a dark blackish-green, and on being stirred shows -a gray or white scum on its surface, while it emits at the same time a -pungent odor. If the vat is only slightly affected, it is sufficient -to add some bran and madder and to let it stand over night. If it has -not quite recovered by morning, it may be necessary to heat it up, -agitate it, and let it stand for a couple of hours, after which -perhaps the addition of a little lime will be necessary. - -If the vat is much sharpened, it is recommended to sink in it a bag of -bran, and leave it over night, when the fermentation will have -restored the vat in a considerable degree; but it will be necessary to -add lime cautiously and by degrees, to bring it to a proper state for -working. - -The theory of the souring of the vat is given. Butyric fermentation -takes place under certain circumstances, butyric acid being formed; -and hydrogen is set free, which reduces the indigo. The addition of -lime makes the vat too strongly alkaline, and sets ammonia free, which -gives the pungent odor of the soured (_verschäften_) vat. -Simultaneously the lime with the white indigo forms a difficultly -soluble compound, which settles, and thus interferes with the working -of the vat. The excess of lime must be removed, which is accomplished -by introducing bran, which causes a lactic fermentation; and the -lactic acid neutralizes the excess of lime, and destroys the lime -compound with indigo which had been formed. The lime may be -neutralized by the use of mineral acids, but there is danger in that -case of precipitating the indigo. - -A second “sickness” is “becoming too sweet.” The symptoms are,—the -blue veins and surface film disappear on stirring, the foam gives a -rustling sound, the bath assumes a reddish-yellow color, blue goods -placed in the bath lose their color, and the vat has an unpleasant odor. - -The vat when “too sweet” needs to be brought to the regular -temperature, and lime to be added cautiously until the vat is brought -to its normal state. It is safer to add an excess of lime and “sour” -the vat, and then bring it back according to the directions under that -head, than to add too little, as less indigo is lost. To use up all -the dye and to dye a light blue, as little lime should be present as -is consistent with the workings of the vat. - -The cause of the “falling away” of the vat is a too active -fermentation, which produces considerable lactic acid, from which -butyric acid forms, setting free hydrogen, thereby making white -indigo, which, if the action is allowed to continue, changes to a -compound from which the indigo cannot be recovered. If lime is added, -the lactic and butyric acids unite with it and precipitate it, while -the excess precipitates the white indigo, which is slowly recovered, -as fermentation progresses, which forms lactic acid, which, taking the -place of the white indigo, sets it free. Besides the sicknesses, there -are various results of mismanagement, of which the first is -overwarming, which causes the bath to turn brown, which is the -beginning of the souring. - -When the bath begins to sour from overheating, some logwood should be -added and then bran, and the vat left to itself over night. The reason -of it is that the temperature is too high for the desired fermentation -to operate. The vat sometimes suddenly turns green, and even when -indigo and the other necessary ingredients are added it remains of -this color. This is called the “breaking up of the vat.” The reason is -that the temperature is too low; to remedy it, it is necessary to add -logwood and bran, warm it up, and stir, when it should stand for some - - - - - -End of the Project Gutenberg EBook of Notes Upon Indigo, by John Hayes - -*** END OF THIS PROJECT GUTENBERG EBOOK NOTES UPON INDIGO *** - -***** This file should be named 62008-0.txt or 62008-0.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/6/2/0/0/62008/ - -Produced by Ronald Grenier. 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You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll -have to check the laws of the country where you are located before using -this ebook. - - - -Title: Notes Upon Indigo - -Author: John Hayes - -Release Date: May 3, 2020 [EBook #62008] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK NOTES UPON INDIGO *** - - - - -Produced by Ronald Grenier. (This file was produced from -images generously made available by The Internet Archive) - - - - - - -</pre> - - -<div class='transnote covernote'> - <p class='c000'><b>Transcriber’s Note:</b></p> - <p class='c000'>The cover image was created by the transcriber and is placed in the public domain.</p> -</div> - -<div class='titlepage'> -<div> - <h1 class="c001"><span class="xlarge">NOTES UPON INDIGO.</span></h1> -</div> - -<div class="nf-center-c0"> -<div class="nf-center c003"> - <div><span class="small">BY</span></div><br /> - <div><span class="large">JOHN L. HAYES,</span></div> - <div class="c003 xsmall">SECRETARY OF THE NATIONAL ASSOCIATION OF WOOL MANUFACTURERS, FELLOW - OF THE AMERICAN ACADEMY, AND CORRESPONDING MEMBER OF THE - ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA.</div> - - <div class="c033 small">From “The Bulletin of the National Association of Wool Manufacturers.”</div> - - <hr class="short" /> - - <div class="c033">BOSTON:</div> - <div>PRESS OF JOHN WILSON AND SON.</div> - <div>1873.</div> - </div> -</div> -</div> - -<div class="section"> -<p class="c008 large">PART I.</p> - -<p><span class="pagenum" id="Page_003">3</span></p> - -<p class="c008 large">NOTES UPON INDIGO.</p> - -<h2 class="nobreak">PART I.</h2> -</div> - -<p> -<span class="smcap">A publication</span> devoted to the interests of the woollen manufacture, -while giving due prominence to its first raw material, wool, cannot -neglect the secondary materials which enter into finished fabrics. The -attractiveness and utility of the largest class of these fabrics are -due to the hue given them by the dyer; and of all the coloring -materials one of the most precious is indigo. In former times, as it -still does at the East, it occupied with madder the place of one of -the two most important of all dyeing materials. Forced of late years -to give way to the marvellous products of modern chemistry, it will -doubtless resume its place under the influence of a more enlightened -economy and a more subdued taste. To contribute to the hastening of -this return is one object of this essay. The most usual reproach -against American fabrics is the want of stability in our dyes,—a -reproach without justice, if applied to American fabrics alone; for -the cheapening of dyestuffs is practised in all the so-called -manufacturing nations, and is contemned alone in the East, from which -we have derived our arts, and by the people whom we despise as -barbarous. To remove this reproach from American fabrics would be -worthy of no little temporary sacrifice on the part of our -manufacturers. -</p> - -<p class="c009"> -The value of indigo as a dyeing material is due to the great stability -of the blue color, and the derivatives from blue, which it gives to -fabrics, especially of wool and cotton. It is not sufficient that a -dyed fabric should preserve its color when -<span class="pagenum" id="Page_004">4</span> submitted to violent tests, -as when acted upon by vegetable or mineral acids or alkaline or soapy -baths: the only stable dyes are those which resist air and light, the -two destructive agents of vegetable colors. Indigo, from the -remarkable manner in which its color becomes fixed upon a fabric, to -be hereafter explained, possesses properties of resistance and -stability in a higher degree than any blue dye. And when we consider -that this blue has not only its own hue, but is the best foundation -for blacks, greens, purples, and even browns, the importance of these -properties cannot be over-estimated. Says M. de Kæppelin, a chemist -and manufacturer of Mulhouse, in one of a series of articles furnished -to the <i>Annales du gênie Civil</i>, 1864: “So high are the properties of -resistance and stability which indigo possesses, that it is perhaps to -be regretted for the art of the dyer and manufacturer of printed -calicoes, that the use of indigo becomes more and more rare, and that -the recent discoveries which modern science has placed at the service -of industry are daily eliminating it from our factories. I have -observed that whenever we have to dye stuffs of a high price, it is -indigo which always serves as a base for the foundation of all the -blue colors, or of those which are derived from blue. It is the same -for the fabrication of printed tissues, which serve for the poorer -classes, whose colors should have great stability without much -increase of cost. But of late years, especially, we find a tendency to -employ colors of little stability, and to prefer them, even in the -class of fabrics first referred to, to those which are more fast, on -account of their vivacity and freshness of tone. It is this tendency, -which the consumer partakes of even while complaining of it, that the -textile manufacturers ought to seek to combat. How often have I heard -the greatest manufacturers of Alsace deplore the obligation which they -felt that they were under of printing their tissues by means of colors -so fugacious and so little resistant as those composed from aniline. -We must hope, then, in the interest of that industry, that while -adopting the marvellous discoveries which science is every day making, -there shall be made a less general application of them, and that we -shall <span class="pagenum" id="Page_005">5</span> return to the fabrication of the styles which necessitate the -more constant employment of coloring materials,—less brilliant, it is -true, but more adherent to the tissues, and less alterable by air and -light. It seems to me, also, that taste would lose nothing; and that -printed stuffs, colored in a manner less brilliant, but more -harmonious, would be perhaps more appreciated, especially by those who -use them.” -</p> - -<p class="c009"> -The tendency to substitute the brilliant for the stable dyes prevails -too much in our own manufacture. A very considerable cloth -manufacturer replied to our inquiry as to the extent to which he used -indigo: “I hardly use it at all; the dye of the indigo blue is not -bright enough to be popular.” On the other hand, we have heard our -leading manufacturer of carpets, whose cultivated taste has led him to -partake of M. de Kæppelin’s views, deplore the introduction of aniline -dyes, as a positive calamity to the textile industry. It is the -influence of the trade, the immediate consumers of fabrics, rather -than the judgment of manufacturers, which promotes the use of the -modern fugacious dyes. The dealers desire not only to imitate the -fashionable colors of European goods, but to secure the utmost -cheapness. One of our largest manufacturers of woollen goods, who had -made a special study of the best processes abroad, and was desirous of -bringing better dyed goods into more general consumption, urged one of -his largest customers, an extensive dealer, to allow him to dye the -waterproof cloakings which he was furnishing for his house, in fast -indigo colors, assuring him that he would charge simply the additional -cost of the indigo, without profit. The offer, which involved the cost -of only a few cents a yard, which would have been gladly paid by the -last consumer if the difference of value had been made known, was -declined. It is not improbable that the inferior goods which the -manufacturer was compelled to furnish were sold to the public as fast -dyed. Our manufacturers, therefore, may not have been responsible for -the predicament in which the most enthusiastic defender of our -protective policy found himself, as we have it from his own lips. -Being about to make a speech in Congress in defence of American -industries, he put on, for the <span class="pagenum" id="Page_006">6</span> first time, a coat declared to have -been made of American cloth. Sitting down, heated and perspiring from -the excitement of his effort, he found that beneath the arms whose -gestures had enforced his eulogies of American industry, the pretended -fast blue of his coat had become <i>red</i>, literally <i>blushing</i> for its -unmerited praise. That fast-dyed goods of the highest excellence can -be and are furnished by American manufacturers, is shown by our army -cloths. The government specifications, copies of which are published -elsewhere in this number, require that all the blue woollen cloth, cap -cloth, and flannels furnished for the army shall be “pure indigo -dyed.” The requisition is strictly enforced. The admirable effect of -this regulation may be witnessed at any dress parade of a battalion of -United States soldiers. The persistency and uniformity of the hue -under constant wear—the cloth of the common soldier in its superior -dye often favorably contrasting with the finer but fancy dyed cloth of -the officer—is one of the circumstances which justify the assertion, -that our army is the best clothed in the world. The contrast is more -remarkable still with the <i>quondam</i> blue cloth, converted by sun -and rain-into every shade of shabbiness, which we purchased in Europe -for our soldiers at the commencement of our late war. -</p> - -<h3>ORIGIN AND EXTRACTION OF INDIGO.</h3> - -<p class="c009"> -Indigo is a coloring material of vegetable origin, which owes its -color and its important applications to a direct blue principle, known -under the name of indigotine. It has been used as a dyestuff from time -immemorial, by the inhabitants of India; and it is from the East, the -cradle of the textile arts, that Europe has derived it. It was -probably received from India by the Greeks, among other products first -made known to them by the expeditions of Alexander the Great. -Dioscorides clearly refers to indigo in mentioning the two coloring -matters brought from India. Pliny mentions a coloring material, having -an admirable mixture of blue and purple, as coming from India, which -he calls <i>indicum</i>. That he refers to indigo is curiously manifest by -the test which he gives, by which the genuine drug might always and -<span class="pagenum" id="Page_007">7</span> -<i>certainly be distinguished from the spurious</i>. This is by putting it -on live coals, when, says he, “the true <i>indicum</i> will burn with a -flame of a most beautiful purple tint.” The purple vapor from burning -indigo is still a characteristic test. The Romans, it is apparent, -used indigo only as a pigment, not knowing what is still the most -important art connected with its use,—how to make it soluble so as to -be available in dyeing. -</p> - -<p class="c009"> -That indigo as a commercial product was first obtained from India is -not only proved by the testimony of Pliny, and other ancient writers, -but is confirmed by a variety of circumstances, and particularly by -its name, which is known to have been <i>nil</i> in the Hindu language, -from the earliest times of which there is mention of it. This name is -still given by the Hindoos to the color blue, and to all the plants -producing indigo. The Arabs and Egyptians, who obtained a knowledge of -indigo from India, adopted the Hindu name, the Arabs calling it <i>nil</i> -or <i>nir</i>, and the Egyptians <i>nil</i> or <i>niel</i>. The Portuguese preserved -the Indian name, with a slight modification, the substance being -called <i>aniliera</i> in their language. The coloring substances -afterwards found in coal-tar having been first found in indigo, modern -science has adopted for them the name of <i>aniline</i>. -</p> - -<p class="c009"> -It has been asserted that this substance was not known in Europe until -the time of the discovery of the passage to India round the Cape of -Good Hope. But Dr. Bancroft has shown that indigo was brought by -merchants from India to Alexandria, and thence to Venice, when that -city was the <i>entrepôt</i> of Europe and the East. It doubtless -contributed to the excellence which the Italian states first attained -in the wool manufacture. The drug was called <i>endigo</i> in Venice, and -it is from that city that we have derived its name and use. It was -imperfectly known in England under its Spanish name in the sixteenth -century, for we find in Hackluyt “Voyages” his instructions to a -traveller who was going to Turkey to ascertain “if <i>anile</i>, that -coloureth blue, be a natural commodity of those parts, and if it be -composed of an herbe.” -</p> - -<p class="c009"> -The general introduction of indigo into Europe was impeded by -legislative enactments, prompted mainly by those employed <span class="pagenum" id="Page_008">8</span> in -industries which it threatened to displace. These were chiefly the -producers of and dealers in <i>woad</i>, formerly used exclusively for -dyeing blue, and the corporation of woad dyers. When dyers from Italy -and Flanders attempted to introduce the superior dyes of indigo, the -woad interests were sufficiently powerful to induce the Elector of -Saxony to denounce the use of the new dyestuff. It was pronounced in -the Diet of the Empire as “a corrosive color,” and “fit food only for -the devil,” <i>fressende teufels</i>. Similar propositions were made in -England and France, in which latter the free use of indigo was not -permitted until 1737. -</p> - -<p class="c009"> -Although indigo as known in the arts is a product of vegetable origin, -we must not omit to notice that one source of its production is the -human body. It was discovered some years since that the blue color -sometimes found in diseased urines, and in certain suppurations, is -due to indigo. Dr. Schunck, in some papers read before the Royal -Society, has shown that it is a frequent constituent of urine secreted -by persons in a healthy state, and that, in fact, it is produced -generally when persons do not take sufficient exercise; and he has -several times succeeded in producing it by taking in his food a rather -large excess of sugar. He has found this substance also in the urine -of beef cattle. It must also be observed that the chemical actions of -indigotine with oxidizing agents, showing indigo to have a very close -relation to aniline and carbolic acid, both products derived from -coal-tar, have produced in the minds of chemists the conviction that -indigotine, like alizarine, the coloring principle of madder, will one -day be artificially produced from coal-tar. -</p> - -<p class="c009"> -The plants which are known to furnish indigo are quite numerous, being -not less than sixty; they do not all belong to the same family, and -none of them contain the coloring principle already formed. The most -important belong to the leguminous family, from which most of the -vegetable dyes are derived, and to the genus <i>indigofera</i>. The species -cultivated and most esteemed are <i>Indigofera tinctoria</i>, <i>I. -disperma</i>, <i>I. anil</i>, <i>I. argentea</i>. -</p> - -<p> -<span class="pagenum" id="Page_009">9</span> -</p> - -<div class="figcenter"> - <img id="image_Indigofera_tinctoria" src="./images/pg001.png" - alt="Drawing of the Indigofera tinctoria plant" /> -</div> - -<p class="c009"> -The principal source of the indigo of commerce is the <i>Indigofera -tinctoria</i>. The accompanying figure is a correct representation of the -plant, and we may dispense with a description of its botanical -characters, observing only that the plant has a half woody stem, and -rises to the height of from three to five feet. The plants exhale a -strong odor towards evening in the fields where they are cultivated. -The leaves have a disagreeable taste, and rapidly putrefy in water. -The plant originated in Campaja, or Guzerat, but is cultivated in -Hindostan, China, Java, and in the East Indies generally. It was -carried by the Spaniards to South America and the West Indies, and it -can be acclimated in all hot countries. The <i>Indigofera argentea</i>, or -indigo plant of Egypt, furnishes the indigo produced in that country -and Arabia. -</p> - -<p class="c009"> -The culture of the plant and the production of commercial indigo is -carried on a vast scale in Lower Bengal. We have before us a large -map, placed at our disposal by an India merchant of Boston, showing -the location of each of the hundreds of factories of that important -centre of production. These factories have been developed by British -enterprise; and India thus receives some slight compensation for the -ruin of her cotton manufacture by the same influence. -</p> - -<p class="c009"> -The propagation of the indigo plant in that country is made by sowing -in a thoroughly tilled silico-argillaceous soil. The seed of the plant -is sowed annually in the spring or autumn, <span class="pagenum" id="Page_010">10</span> according to the variety -used, some germinating more slowly, and requiring to remain in the -ground longer than others. The time of putting in the seed is also -governed by the nature of the soil and its position in respect to -neighboring rivers. In the lowlands subject to inundations, the indigo -ought to be all cut at the period of the rains and inundations, which -would destroy the crop in a brief time. Besides, during the rainy -period the planter has at his disposal sufficient water to commence -his operations of fabricating the indigo, which is the suitable time -for beginning the cutting of the plant. The time of cutting the -indigo plants is therefore regulated by the elevation of the land and -danger from floods. The high lands are always sowed several weeks -after those subject to inundations. -</p> - -<p class="c009"> -The Chinese prick out the young plants in parallel rows, always -preserving the land quite clear of weeds. By taking away the blossoms -of the plant before their development, they increase the growth of the -leaves, and, consequently, the return of indigo; for it is in the -leaves principally that the coloring material is found. -</p> - -<p class="c009"> -In certain localities the planters break off the leaves which have -acquired a bluish green tint. But more frequently the whole plant is -cut down close to the ground in the months of June or July, when the -flowers begin to open. The portion of the plant which remains pushes -up quite rapidly, and furnishes a second, and even third, and -sometimes, though rarely, a fourth cutting. The quality of the product -diminishes according to the number of the cuttings. -</p> - -<p class="c009"> -The plant called <i>nil</i>, cut down to the root and gathered up in -packages, is worked up the same evening. The package is formed from -the product of a space of land embraced by a chain about three yards -long. The value of the first material changes with the value of the -soil. Thus, one soil produces a plant which has many stems and few -leaves, while another gives many leaves and few stems. The richness in -coloring material depends upon the quantity of leaves, but varies also -with an equal weight of leaves with atmospheric influences. Thus -regular dealers in the article observe a marked difference in the -quality of indigo in different seasons. -</p> - -<p> -<span class="pagenum" id="Page_011">11</span> -</p> - -<p class="c009"> -M. A. Koechlin Schwartz has recently published some interesting notes -upon the preparation of indigo in Lower Bengal. In that country, which -furnishes excellent indigo, the factory includes, besides filters, -presses, a steam-engine, drying apparatus, and reservoir of water, two -lines of vats, arranged one above the other, from fifteen to twenty in -each line. These vats are built up with bricks, and covered with a -strong coat of solid and well made stucco. They are square, about six -yards on a side, and about a yard deep. The back row is about a yard -above the front one. The plant is fermented in the vats of the upper -row; when the operation of fermentation is terminated, a faucet is -opened, and the liquid is run into the lower vat. The water of the -Ganges, which is relatively pure, and thus well suited for this work, -is brought into basins of deposition, where it becomes clarified, and -is distributed by a common canal to the vats of the upper row. The -plants, cut in the morning and bound up into packages, come to the -factory after midday, and are thrown into the vat in the evening. A -vat contains one hundred packages carefully arranged, one beside the -other; heavy timbers are placed upon the plants, which are pressed -down by means of large wedges. It is necessary that the plants should -be pressed together very compactly, as without this the fermentation -does not take place to advantage. At nightfall the water is introduced -into the vats, and fills them so as completely to submerge the plants. -The fermentation is more or less prolonged according to the -temperature. Its duration varies from nine to fourteen hours. The -workmen judge as to the procedure of the operation by withdrawing a -little of the liquid in the lower vat. If it is of a clear pale yellow -when withdrawn, it will furnish a product less abundant but more pure -than if of a deep gold color. -</p> - -<p class="c009"> -At the moment of its issue from the fermenting vat the liquid is of a -yellow color, more or less deep. The liquid is allowed to remain -undisturbed for a brief period, when twelve naked men, armed with long -bamboos, enter the vat to beat the water while it is still warm. -During this time the upper vat is emptied and cleaned out for the -succeeding operation. One vat requires <span class="pagenum" id="Page_012">12</span> seventeen workpeople (twelve -men and five women). They thrash the water for two or three hours. The -liquid passes by little and little to a pale green, and the indigo is -found on suspension in the form of small floccules. The liquor is -suffered to remain undisturbed for half an hour; it is then gradually -decanted by opening, one after the other, the discharging holes placed -at different heights. The water returns to the river, and the -precipitate, under the form of a thin <i>bouille</i>, is turned into a -reservoir. This <i>bouille</i> is pumped up into a vessel, and made to boil -for a moment to prevent a second fermentation, which would injure the -quality of the product, by turning it black. It is suffered to rest -about twenty hours, and the next morning it is again subjected to -boiling, the ebullition being kept up three or four hours. The boiling -deposit is then turned off upon a large filter, through which the -water drips. This filter is composed of a vat constructed of masonry, -covered with stucco, about eighteen feet long by six feet wide and -three feet deep. This is covered with bamboos, upon which is a grating -of smaller reeds, and above by a stout strained cloth. There remains -upon the cloth a thick paste, of a deep blue and nearly black color. -The water which is run into the vat deposits some indigo which has -pressed through the filter. This is decanted after being allowed to -rest, and the turbid liquid is boiled the next day with the fresh -indigo. -</p> - -<p class="c009"> -The paste of the filter is introduced into some small boxes of wood, -pierced with holes, and provided above and below with a strong cotton -cloth. The whole is again covered with a piece of stuff, and then with -a covering of wood, pierced with small holes, and it is placed under a -press, the force being gradually applied, so as to cause the water to -run out as much as possible. There is withdrawn from the box a cake of -the size of a cake of Marseilles soap. The water squeezed out flows -back into the filtering vat, to be boiled again with the fresh indigo. -The drying of the cakes ought to be done very slowly. -</p> - -<p class="c009"> -The dry-house is a large building of masonry, quite high, and pierced -with many openings, provided with narrow blinds, to prevent the direct -light of the sun from penetrating into the <span class="pagenum" id="Page_013">13</span> interior. Care is taken -also to surround the dry-house with large shade-trees. The cakes take -from three to four days to dry, after which they are packed in small -boxes and carried to Calcutta, the great market of Bengal. -</p> - -<p class="c009"> -The details above given apply to the factories managed by European -planters. The natives operate in nearly the same manner, but with less -care, and consequently their products are inferior. The average -product of indigo in Lower Bengal is stated at 4,000,000 kilograms, or -8,840,000 pounds per year. The most remarkable fact to be noticed in -these operations is, that the blue principle is developed by chemical -action from certain absolutely colorless principles existing in the -plant. The theory of the change effected is still somewhat in doubt, -because no chemist has studied the fresh plant, and observed upon the -spot the phases of the operation of the production of indigo on a -large scale. But the most accepted theory is that derived from the -researches of Dr. Schunck, upon the <i>isatis</i> or woad-plant, which -produces indigotine in a much less degree than the true indigo plants; -viz., that the indigo exists in the plants combined with sugar, -forming a glucoside, to which he gives the name <i>indican</i>. This -compound, under the influence of fermentation in the manufacturing -process, is supposed to be unfolded into indigo and sugar. -</p> - -<p class="c009"> -Without dwelling upon this question, which is beyond our province, we -observe that the plants of the genus <i>indigofera</i> are used for the -production of commercial indigo, on account of the greater richness in -the coloring principle. Other plants, which furnish the same coloring -principle, indigotine, are more frequently used directly in dyeing to -furnish the blue principle than they are for the production of indigo. -</p> - -<p class="c009"> -The most important of these plants, although there are others, such as -the <i>Polygonum tinctorium</i> and the <i>Nerium tinctorium</i>, is the <i>Isatis -tinctoria</i>, which produces pastel, or woad. This, plant belongs to the -family of cruciferæ, and is a biennial. It is represented in the -accompanying figure. -</p> - -<p> -<span class="pagenum" id="Page_014">14</span> -</p> - -<div class="figcenter"> - <img id="image_Isatis_tinctoria" src="./images/pg002.png" - alt="Drawing of the Isatis tinctoria plant" /> -</div> - -<p class="c009"> -The leaves which surround the stem are collected in May or June of the -second year, when they begin to turn yellow. The wasted and dried -leaves are sometimes used directly for dyeing, but more generally the -leaves, after being cut and dried, are carried to a mill, and then -ground to a paste, after which it is formed into a mass or heap, and -being covered to protect it from rain, is left to undergo a partial -fermentation for about a fortnight. The heap is then well mixed and -formed into balls, which are exposed to the sun and wind to dry, and -thereby prevent the putrefaction which would otherwise take place. -Being afterwards collected in heaps, these balls again ferment, become -hot, and emit the odor of ammonia, which Hume tells us, in the History -of England, gave such offence to Queen Elizabeth that she issued an -edict to prohibit the cultivation of this plant. After the heat has -continued for some time, these balls fall into a dry powder, in which -form the woad is usually sold to the dyer. The best French woad comes -from Provence, Languedoc, and Normandy. In Germany, the pastel of -Thuringia is used almost exclusively; <span class="pagenum" id="Page_015">15</span> the packages have the trade-mark -of three towers, with the numbers 4, 5. In this country, owing -probably to the prejudices of practical dyers, who have generally come -from England, the Lancashire woad is almost exclusively used. The very -little imported of late years, ranging from two thousand to twelve -thousand dollars annually in value, is used for mixing with indigo in -the so-called woad vat, to be hereafter described. -</p> - -<h3>COMMERCIAL INDIGOES.</h3> - -<p class="c009"> -The following description of the indigoes of commerce is taken -principally from Schutzenberger’s excellent treatise on coloring -materials. It coincides very nearly with that given by Napier from -Dumas and Chevrueil. Indigoes are classed, according to their origin, -into three groups. -</p> - -<p class="c009"> -1. Indigoes of Asia (from Bengal, Oude or Coromandel, Manilla, Madras, -and Java). -</p> - -<p class="c009"> -2. Indigoes of Africa (Egypt, Island of France, Senegal). -</p> - -<p class="c009"> -3. Indigoes of America (Guatemala, Caraccas, Mexico, Brazil, and the -West Indies). -</p> - -<p class="c009"> -The three varieties in most esteem are those of Bengal, Java, -and Guatemala. -</p> - -<p class="c009"> -<i>Indigoes of Java</i>.—These are distinguished by the great purity of -their coloring material. They contain the minimum of extractive -organic matter. If, in spite of this, they do not give a high yield of -indigotine; this is owing to a mixture of silicious mineral substances -with their paste. The paste is soft. It adheres strongly to the -tongue, and its density is feeble. They are generally of a pure blue, -light or ash colored in the kinds which are less rich, and of a -magnificent violet blue in the superior qualities. The last take a -beautiful copper color when scratched by the nail. They are placed in -the very first rank among all indigoes in respect to fineness and -beauty, if not in richness in the blue coloring principle. Their -purity, complete absence from carbonate of lime, and the small -quantity of foreign organic materials which they contain, cause them -to be much sought for, for the preparation of <i>carmine</i> of indigo. The -consumption of the Javan indigoes in this country is so small as not -to be appreciated. -</p> - -<p> -<span class="pagenum" id="Page_016">16</span> -</p> - -<p class="c009"> -<i>Bengal Indigoes</i>.—These are the indigoes <i>par excellence</i>, for in -them are found the most varied qualities, from the most beautiful and -rich to the most ordinary. The superior qualities are of a deep violet -blue, with a fine and uniform paste; they adhere to the tongue, are -easily pulverized, and take a beautiful coppery tint when scratched by -the nail. The fresh fracture shows a magnificent purplish blue -reflection. Their yield in indigotine does not surpass seventy-two per -cent. -</p> - -<p class="c009"> -After these come the reddish-violet indigoes with a purplish hue, and -a fracture more uniform and shiny. They are also more dense and hard -than the superior qualities. The reddish hue does not proceed from the -greater or less amount of coloring material contained, but from the -presence of a greater quantity of brown and red extractive matter. -These qualities are not to be despised, for the kinds which give the -best results in the dyeing vat are found in these indigoes. It would -seem, in fact, says the author whom we are following, “that the browns -and reds of indigo play an important part in vat dyeing, that they are -able to become dissolved and to fix themselves upon the tissues at the -same time as the indigotine, and thus operate to reinforce the hue. -The fact is, that dyers generally prefer the reddish indigoes to the -other varieties.” Among the Bengal indigoes there is found a clear -blue variety, less rich in coloring matter, but also more exempt from -organic substances. The impurity is constituted by mineral matters. It -is less dense, adheres strongly to the tongue, and does not take a -coppery hue, like the other varieties, when scratched by the nail. -</p> - -<p class="c009"> -The worst qualities of the Bengal indigoes, as in all the species, are -the clear blues, shading on to gray or green. This coloration denotes -a great quantity of extractive matter different from the indigo brown -which characterizes the red varieties, and completely inert. These -indigoes are hard, dense, adhere little or none to the tongue, and do -not show coppery reflections when scratched. -</p> - -<p class="c009"> -The most skilful connoisseurs distinguish forty-three varieties -of Bengal indigo. The most important are the following:— -</p> - -<p class="c009"> -1. <i>Superfine blue, light or floating</i>.—Color bright blue; <span class="pagenum" id="Page_017">17</span> light, -friable, and spongy; adherent to the tongue, soft to the touch, -showing coppery reflections when rubbed by the nail; paste uniform and -pure. -</p> - -<p class="c009"> -2. <i>Fine blue</i>.—Like the preceding, but the color a little less vivid. -</p> - -<p class="c009"> -3. <i>Violet blue</i>.—A little less light and friable. Has a violet blue. -</p> - -<p class="c009"> -4. <i>Superfine violet</i>. -</p> - -<p class="c009"> -5. <i>Superfine purple</i>. -</p> - -<p class="c009"> -6. <i>Fine violet</i>. -</p> - -<p class="c009"> -7. <i>Good violet</i>. -</p> - -<p class="c009"> -8. <i>Red violet</i>. -</p> - -<p class="c009"> -9. <i>Ordinary violet</i>. -</p> - -<p class="c009"> -10. <i>Good soft red</i>. -</p> - -<p class="c009"> -11. <i>Good red</i>. -</p> - -<p class="c009"> -12. The indigoes, <i>fine coppery, good coppery, ordinary coppery, and -low coppery</i>. -</p> - -<p class="c009"> -<i>The Indigoes of Oude and Coromandel</i>.—These are made in the interior -of Hindostan. Those of the best quality correspond to the middling -Bengal indigoes, and are met with in square masses, having an even -fracture, but are more difficult to break; the inferior qualities are -heavy, of a sandy feel, having a blue color, bordering on green or -gray, or even black; often in large squares, and covered with a slight -crust or rind of a greenish color. They are the most difficult to -break of all the indigoes of commerce. -</p> - -<p class="c009"> -<i>Madras Indigoes</i>.—They have a grained fracture, and are of a cubical -figure. The superior qualities have no rind. The qualities are fine -blue, mixed violet blue, and ordinary. They are all lighter, and less -rich in coloring matter than the Bengal indigoes. -</p> - -<p class="c009"> -<i>Manilla Indigoes</i>.—These occur in cubical blocks, flat squares, or in -irregular pieces. They are light, with a fine paste, and of a clear -blue. They effervesce with acids, showing the presence of carbonate of -lime incorporated in their paste. They are consequently poor in -coloring material, and are hence almost exclusively used as a bluing -material in washing fabrics. -</p> - -<p> -<span class="pagenum" id="Page_018">18</span> -</p> - -<p class="c009"> -<i>American Indigoes</i>. <i>Guatemala</i>.—These indigoes are produced now -altogether in Hunduras, although they still retain in commerce the -name of Guatemalan. They are generally found in small pieces, -irregular in form and size, and come in envelopes of skin containing -about half as much as the Bengal chests. Putting aside the difference -in exterior form, these indigoes approach very closely to those of -Bengal. The same qualities are found, only they are more frequently -mixed. The clear blue is more rare, and, when it is found, it is -poorer in coloring matter. In purchasing these indigoes it is -necessary to beware of the reds, which often contain a strong -proportion of the brown extractive matter. It is not rare to find -among the Guatemalan indigoes beautiful specimens of the blue violet, -equal to the richest Bengal variety. Unfortunately, this superior -variety is generally mixed with inferior kinds, as to have less value. -The American indigoes are classified as follows:— -</p> - -<p class="c009"> -<i>Guatemala floro</i>.—Bright blue, paste uniform, soft and light. This -variety, in Bancroft’s time, was the most esteemed of all indigoes. -</p> - -<p class="c009"> -<i>Guatemala sobresaliente</i>.—Less light, the paste firmer and the blue -less beautiful. -</p> - -<p class="c009"> -<i>Guatemala corte, or copper-colored</i>.—Paste less firm and heavier, -coppery red. -</p> - -<p class="c009"> -<i>Caraccas</i>.—These resemble very much the Guatemala varieties. The -qualities are designated by analogous names, but they are, in general, -less esteemed than the preceding. -</p> - -<p class="c009"> -<i>Mexican</i>.—They hold an intermediary rank between the -Caraccas and Mexican. -</p> - -<p class="c009"> -<i>Brazil</i>.—These indigoes are in small rectangular parallele-piped -masses, or in irregular lumps of a greenish gray color externally, and -having a smooth fracture, a firm consistency, and a copper-colored -tint of greater or less brilliancy. -</p> - -<p class="c009"> -<i>The indigoes of Africa and Egypt</i>.—These have only been manufactured -within the last twenty years; they are in flat squares. The paste is -fine and quite light, and the color pure blue or bordering on violet. -The varieties are distinguished as fine blue and good violet and red. -</p> - -<p><span class="pagenum" id="Page_019">19</span> -</p> - -<p class="c009"> -<i>Indigoes of the Isle of France and Senegal</i>. Rare in commerce, but -of good quality. -</p> - -<p class="c009"> -The indigoes of the inferior qualities, characterized by a salt-like -color, bordering more or less upon green; by a coarse, uneven, and -very dense paste; by not adhering to the tongue, and by not showing a -coppery color when scratched,—can never be employed to advantage, -notwithstanding their low price. The purchaser of these qualities must -be guided solely by the results of analysis; for an article is found -in commerce whose richness in indigotine does not exceed twelve to -fourteen per cent. The presence of so high a proportion of foreign -matter prevents the chemical change which the indigo ought to undergo -in the dyeing vat; and this foreign matter, added to the deposits of -the dyeing vats, causes great loss of the coloring matter. These -indigoes should be used as little as possible, especially in the cold -vats used for dyeing cotton and linen. The middle varieties of the -Bengal and Guatemala indigoes, and, above all, the red varieties, -produce in the cold vats the most advantageous results. The lower -qualities above spoken of present less inconvenience in the hot vats -used for dyeing wool; and it is for this purpose that they are -generally used. In considering the previous observations, the wool -manufacturer may arrive at this conclusion: that while he can, with -less loss than the maker of cotton fabrics, make use of the lowest -qualities of indigo, he will obtain <i>the best results from the middle -qualities of the reddish Bengal indigoes</i>. -</p> - -<p class="c009"> -The skilled dealers in indigo recognize not only the above -distinctions, founded upon the country of production, color, and -physical qualities, but they observe whether the article has any of -the following defects, which are designated by certain well-understood -terms: such as whether the indigo is <i>sandy</i>,—when brilliant points -are observed in the interior, which are in reality particles of sand; -<i>spotted</i>, that is to say, of unequal tint, and marked by small -blackish points; <i>ribboned</i>, marked by transversal bands of a paler, -and sometimes red color; <i>burnt</i>, the pieces having a scorched -appearance, due to rapid drying, and <span class="pagenum" id="Page_020">20</span> separating into small black -fragments under the pressure of the hand; <i>crumbly</i>, when in pieces of -irregular figure, proceeding from fractures of the squares; <i>cold</i>, -when the indigo does not adhere to the tongue. The above -classification is presented with a full knowledge that these -distinctions are by no means recognized in the ordinary commerce in -this article. It is not, however, without interest as an illustration -of the minute attention given to this subject in Europe, where a -higher manufacture requires a nicer investigation of the qualities of -materials employed. -</p> - -<h3>DETERMINATION OF THE RICHNESS AND PURITY OF INDIGOES.</h3> - -<p class="c009"> -It is evident that the commercial form and the high price of this drug -favor fraud, and the desire to illicitly introduce foreign substances -into the paste. It is important, therefore, that the purchaser should -carefully ascertain the actual value of the article which he is to -use. He should know not only the proportion of indigotine contained, -which varies in the commercial indigoes from twelve to seventy-five -per cent, but the hardness and density. A good indigo ought to have -qualities which can be recognized by the eye and touch alone. The -first and the only examination ordinarily made by purchasers is in -respect to the physical qualities of the article. Different pieces are -selected, and their fresh fracture is attentively observed. The -purchaser observes whether the squares are like each other, and if the -parts of the same piece present the same tint. He determines the -porosity by the simple means of applying his tongue to the fresh -fracture. The more rapid the adherence of the tongue, the more porous -the indigo. By scratching the piece with his finger-nail, he -determines the extent of the coppery reflection, — an important test. -</p> - -<p class="c009"> -From all these characters, taken together, the purchaser can form -quite a correct idea of the value of indigoes in general; and the -greater number of dyers, both in Europe and this country, are -satisfied to make their purchases with only this physical examination. -The most experienced dealers in this country <span class="pagenum" id="Page_021">21</span> make no other examination -than the physical one. An eminent indigo broker in Boston has -permitted me to copy the following memoranda for the physical -examination of indigo from his notebook. -</p> - -<div class="c039"> -<p class="c009 c040"> -The chief signs of good indigo are its lightness, feeling dry when -touched, and, when broken, appearing of a beautiful violet blue. Good -indigo swims in water; if thrown upon burning coals it emits a -violet-colored smoke, and leaves but little ashes. -</p> - -<p class="c009"> -In selecting indigo the large regularly formed cakes should be -preferred,—those of a fine, rich blue color, extremely free from the -white adhesive mould,<a - id="FNanchor_1"></a> <a href="#Footnote_1" - class="fnanchor">[1]</a> and of a clean, neat shape. When broken, it -should be of a bright purple cast, of a close and compact texture, -free from specks or sand, and when rubbed with the nail should have a -beautiful shiny coppery appearance; when burnt in a candle it should -fly like dust; that which is heavy and dull colored should be -rejected. Indigo is estimated and classed in commercial language, as -follows: fine blue, ordinary blue, fine purple, inferior purple, and -violet, strong copper, and ordinary copper. It is purchased by the -factory maund (74⅔ lbs. The Bazaar maund is 82²⁄₅₀ lbs.), packed in -cases containing on an average 2¼ cwt., dammered (pitched) and covered -with gunny bagging. -</p> -</div> - -<p class="c009 c040"> -Still, in making large purchases, as a measure of wise precaution the -chemical test should be added. This is used to ascertain the -proportion per cent of indigotine which a given indigo has. The -determination of the quality of indigotine contained is not alone -sufficient to fix the value of an indigo. With an equal yield of -indigotine, the indigoes are always to be preferred which have a light -and soft paste; and for the preparation of the indigo vat the -preference should be always given to the violet red rather than to the -clear blue indigoes. -</p> - -<p class="c009"> -The chemical works which treat of this subject give elaborate details -of a great number of processes for determining by chemical tests the -amount of indigotine, or the coloring material in indigoes. To give -these numerous processes would only <span class="pagenum" id="Page_022">22</span> confuse the reader. In our own -confusion upon this subject we submitted the descriptions of these -various processes to one of the most eminent and practical of American -chemists, Dr. Charles T. Jackson, an official State Assayer for the -State of Massachusetts, who has had much experience in testing indigo, -with a request that he would describe the process which he approves -and practises. He has obliged us by the following communication:— -</p> - -<p class="right"> -<span class="smcap">Boston</span>, Nov. 21, 1872.<br /> -No. 47 Court Street, Room 4. -</p> - -<p> -<span class="smcap">John L. Hayes</span>, Esq. -</p> - -<p class="c009"> -<span class="smcap">Dear Sir</span>,—In reply to your inquiry as to the simplest method of -analyzing indigo, I would say that I first ascertain the amount per -cent of earthy matters and metallic oxides, in the samples brought to -me, by burning a weighed quantity in a counterpoised platinum -crucible, until all organic matters are removed or consumed, and then -weighing the ashes obtained. The ash is then subjected to analysis in -the usual way, and lime, alumina, peroxide of iron, and some other -earthy impurities are separated. -</p> - -<p class="c009"> -Then, to determine the amount of coloring matter, or indigotine, I -make use of a standard sample of pure reduced indigo, which is -dissolved in the most concentrated sulphuric acid, and diluted with -water after solution. Then I ascertain how much bleaching powder -(chloride of lime) is required to dissolve the solution. This is the -quantity required for absolutely pure indigo. -</p> - -<p class="c009"> -Now, the indigo of commerce does not contain more than say from forty -or fifty per cent of pure indigotine, and of course will require a -smaller quantity of bleaching powder to decolor it; or the quantity of -bleaching powder to decolor a given weight of pure indigo may be -weighed out, and the sample to be compared having been dissolved in -strong sulphuric acid, and diluted with water, is to be poured in and -stirred or shaken well until the point of decoloration is ascertained. -In this case it is best to weigh out at least twice as much of the -sample to be tested as was used of pure indigo, and to measure the -solution in a graduated glass vessel,—an alkalimeter, for example,—so -that by measure we may know exactly how much of the sample we add to -the solution of bleaching powder. Thus the relative coloring values of -the samples may be readily ascertained. -</p> - -<p class="c009"> -If you have no purified indigo on hand, you can make a good -<span class="pagenum" id="Page_023">23</span> -comparative trial of your samples against a perfectly good sample of -Bengal indigo, which may be kept for a standard of comparison. Very -useful practical results may thus be obtained. -</p> - -<p class="c009"> -It is well, however, to keep on hand a standard sample of pure indigo, -prepared from reduced or white indigo, as directed by Berzelius (vol. -vi. page 3, French ed., 1832), and in Muspratt’s Chemistry applied to -the Arts (Dyeing, Indigo). -</p> - -<p class="c009"> -In the analysis by reduction of indigo, the process is simply as -follows: Reduce the indigo to fine powder, and weigh it; weigh out an -equal quantity of pure quicklime (made from pure white marble). -Measure in a graduated vessel a certain volume of water. Slack the -lime with a portion of this water. The rest of this water is to be -used in rubbing up the indigo in a mortar. Then the slacked lime is to -be mixed with the indigo, rubbing the substances well together. -Introduce the whole into a large flask; 1½ to 2 litres (about 3 to 4½ -pints) of water is required for 1 gramme (or about 15 grains of -indigo). The flask and contents are then to be exposed to a heat of -from 176° to 190° F. for some hours. This is best effected in a water -bath. By this digestion the lime is made to combine with the indigo -brown, and the coloring matter is set at liberty. Dissolve in the -liquor a little protosulphate of iron, exempt from copper, and reduced -to a fine powder. The flask is to be corked and well shaken, and -allowed to cool. When the sediment is settled, decant the clear -solution by means of a syphon into a graduated glass. The coloring -matter oxidizes by exposure to the air; and to favor this oxidation -and to keep the lime in solution, add muriatic acid to the liquor. -When the liquor has become clear, filter and collect the precipitate -on a weighed filter, which wash with hot water, and dry at a -temperature of 212° F. Thus we can learn, by weighing the filter -again, how much indigotine is contained in the sample. -</p> - -<p class="c009"> -If we make use of 200 measures of water, and have drawn off 50 -measures of the solution to oxidate, and this 50 measures has produced -10 grains of indigo, the whole sample evidently contained 40 grains of -indigo blue. -</p> - -<p class="c009"> -This method serves both for an assay of the sample and the production -of a standard sample of pure indigotine. The operation may be carried -on upon a larger scale for the manufacture of a standard sample. -</p> - -<p class="c036">Yours truly, -</p> - -<p class="c007"><span class="smcap">C. T. Jackson.</span> -</p> - -<p><span class="pagenum" id="Page_024">24</span> -</p> - -<p> -Dr. Jackson adds the following note:— -</p> - -<p class="c009"> -In the processes given I have not referred to the qualitative analysis -or testing for all the kinds of adulterations, but have given only -valuation of the coloring power of indigo. -</p> - -<p class="c009"> -I have had occasion to search indigo for Prussian blue, an occasional -adulterant. This is ascertained by caustic potash, which becomes in -part an oxide if Prussian blue is present. This acidulates with -muriatic acid, and, tested with sulphate of iron, proves, by formation -of Prussian blue, the presence of the ferrocyanide of potash in the -solution, and hence Prussian blue in the indigo. Lime and clay are the -usual adulterants, and oxide of iron is often present accidentally or -from the clay adulterants. Starch and flour are rarely used, as they -add little to the weight. -</p> - -<p class="c007">C. T. J. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_1"></a><a href="#FNanchor_1"> -<span class="label">[1]</span></a> -<p class="c009"> -Many experienced purchasers in this country pay no regard to this -mould, as it weighs scarcely any thing.—<span class="smcap">Ed.</span> -</p> -</div> - -<h3>COMMERCE IN INDIGO.</h3> - -<p class="c009"> -Before proceeding to a consideration of the practical applications of -indigo in manufacturing, we must pause to make some general -observations upon the commerce in indigo. -</p> - -<p class="c009"> -The first European impulse given to this commerce was made by the -Spanish and Portuguese. They not only imported indigo from the Indies, -but established its fabrication in their colonies. To them we owe its -production in Guatemala, Caraccas, and Brazil. The French exported -from the Island of San Domingo, only, in 1774, 2,350,000 pounds weight -of this commodity. British influence was exerted in favor of the -development of this article in the American colonies, and, in 1773, in -the space of twelve months, over a million pounds of indigo were -exported from South Carolina. The production in India was at that time -of little importance. It was not until 1783 that the attention of the -English was directed to the culture of indigo in India for European -consumption, that produced by the natives being all consumed in their -own manufactures. In the hands of the English this product rapidly -rose to be the most important of India, in a commercial view, except -that of rice. The small cost of a factory, and the comparatively small -capital required for <span class="pagenum" id="Page_025">25</span> this production, caused the indigo culture to be -preferred to sugar planting. The importation and sale of this -commodity at the East India House, in 1792, amounted to 581,827 lbs., -while the importation into Great Britain from other parts of the world -amounted to 1,285,927 lbs. In 1806 the importation from the East -Indies, and sales at the East India House, amounted to 4,811,700 lbs., -and produced in sterling money £1,685,275. In the year 1862–63, the -export from India, and the destination of supplies, were as follows:— -</p> - -<table class="table5" summary="Destination"> - <tbody> - <tr> - <td class="btd bbt brt c019 small">Destination.</td> - <td class="btd bbt brt c019 small" colspan="2">Quantity.</td> - <td class="btd bbt c019 small">Value.</td> - </tr> - <tr> - <td class="c006 brt small">United Kingdom</td> - <td class="c022 small">8,537,133</td> - <td class="c007 brt small">lbs.</td> - <td class="c023 small">$1,627,035</td> - </tr> - <tr> - <td class="c006 brt small">America</td> - <td class="c022 small">134,064</td> - <td class="c007 brt small"></td> - <td class="c023 small">26,949</td> - </tr> - <tr> - <td class="c006 brt small">Arabian and Persian Gulfs</td> - <td class="c022 small">343,037</td> - <td class="c007 brt small"></td> - <td class="c023 small">33,385</td> - </tr> - <tr> - <td class="c006 brt small">France</td> - <td class="c022 small">1,922,120</td> - <td class="c007 brt small"></td> - <td class="c023 small">371,396</td> - </tr> - <tr> - <td class="c006 brt small">Germany</td> - <td class="c022 small">85,680</td> - <td class="c007 brt small"></td> - <td class="c023 small">15,504</td> - </tr> - <tr> - <td class="c006 brt small">Suez</td> - <td class="c022 small">295,269</td> - <td class="c007 brt small"></td> - <td class="c023 small">51,730</td> - </tr> - <tr> - <td class="c006 brt small">Other places</td> - <td class="c022 small">9,577</td> - <td class="c007 brt small"></td> - <td class="c023 small">815</td> - </tr> - <tr> - <td class="c006 btt brt bbt small">Total</td> - <td class="c022 small btt bbt small">11,326,880</td> - <td class="c007 btt bbt brt small">lbs.</td> - <td class="c023 small btt bbt small">$2,126,814</td> - </tr> - </tbody> -</table> - -<p class="c009"> -The value of exports in 1866 was £1,861,501. In the same year the -imports of indigo from the whole of Central America, including -Honduras, was 672,480 lbs. The consumption of indigo in Great Britain -did not increase during the ten years ending with 1867. This -stationary demand, notwithstanding the fall in the price of the drug -and increase of population, is attributed by McCulloch principally to -the decreasing use of blue cloth. It is more probably due to the -substitution of cheaper dyes. The average home consumption in Great -Britain for seven years ending in 1867, was 1,675,072 lbs. per year. -</p> - -<p class="c009"> -The importation into this country for the twenty years last past is -shown by the following table, kindly prepared at our request by the -chief of the Bureau of Statistics:— -</p> - -<p><span class="pagenum" id="Page_026">26</span> -</p> - -<p class="c008"><i>Statement of Imports of Indigo into the United States during the -Fiscal Years ended June 30, 1853–1872.</i> -</p> - - -<table class="table5" summary="US Imports"> - <tbody> - <tr> - <td class="btd bbt brt c019 xsmall" rowspan="2">Fiscal Years<br />ended June 30.</td> - <td class="btd bbt c019" colspan="4">INDIGO.</td> - </tr> - <tr> - <td class="c019 bbt brd small" colspan="2">FREE OF DUTY.</td> - <td class="c019 bbt small" colspan="2">DUTIABLE</td> - </tr> - <tr> - <td class="c022 brt small"></td> - <td class="c019 brt small">Pounds.</td> - <td class="c019 brd small">Dollars.</td> - <td class="c019 brt small">Pounds.</td> - <td class="c019 small">Dollars.</td> - </tr> - <tr> - <td class="c022 brt small">1853</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,387,847</td> - <td class="c023 small">947,367</td> - </tr> - <tr> - <td class="c022 brt small">1854</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,965,789</td> - <td class="c023 small">1,282,367</td> - </tr> - <tr> - <td class="c022 brt small">1855</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">2,097,397</td> - <td class="c023 small">1,151,516</td> - </tr> - <tr> - <td class="c022 brt small">1856</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,732,290</td> - <td class="c023 small">1,063,743</td> - </tr> - <tr> - <td class="c022 brt small">1857</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,533,037</td> - <td class="c023 small">1,010,509</td> - </tr> - <tr> - <td class="c022 brt small">1858</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,647,767</td> - <td class="c023 small">945,083</td> - </tr> - <tr> - <td class="c022 brt small">1859</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,773,868</td> - <td class="c023 small">1,441,429</td> - </tr> - <tr> - <td class="c022 brt small">1860</td> - <td class="c022 brt small"></td> - <td class="c022 brd small"></td> - <td class="c022 brt small">1,707,116</td> - <td class="c023 small">1,413,790</td> - </tr> - <tr> - <td class="c022 brt small">1861</td> - <td class="c022 brt small">185,039</td> - <td class="c022 brd small">160,138</td> - <td class="c022 brt small">719,563</td> - <td class="c023 small">505,766</td> - </tr> - <tr> - <td class="c022 brt small">1862</td> - <td class="c022 brt small">2,501,052</td> - <td class="c022 brd small">3,281,441</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1863</td> - <td class="c022 brt small">885,834</td> - <td class="c022 brd small">1,008,187</td> - <td class="c022 brt small">178,364</td> - <td class="c023 small">219,169</td> - </tr> - <tr> - <td class="c022 brt small">1864</td> - <td class="c022 brt small">684,813</td> - <td class="c022 brd small">623,406</td> - <td class="c022 brt small">897,821</td> - <td class="c023 small">671,899</td> - </tr> - <tr> - <td class="c022 brt small">1865</td> - <td class="c022 brt small">741,438</td> - <td class="c022 brd small">601,283</td> - <td class="c022 brt small">415,575</td> - <td class="c023 small">324,207</td> - </tr> - <tr> - <td class="c022 brt small">1866</td> - <td class="c022 brt small">798,855</td> - <td class="c022 brd small">609,160</td> - <td class="c022 brt small">44,660</td> - <td class="c023 small">41,268</td> - </tr> - <tr> - <td class="c022 brt small">1867</td> - <td class="c022 brt small">1,069,506</td> - <td class="c022 brd small">816,974</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1868</td> - <td class="c022 brt small">870,164</td> - <td class="c022 brd small">775,751</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1869</td> - <td class="c022 brt small">1,574,449</td> - <td class="c022 brd small">1,649,550</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1870</td> - <td class="c022 brt small">1,270,579</td> - <td class="c022 brd small">1,203,664</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1871</td> - <td class="c022 brt small">1,994,172</td> - <td class="c022 brd small">2,052,222</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt small">1872</td> - <td class="c022 brt small">1,526,869</td> - <td class="c022 brd small">1,484,744</td> - <td class="c022 brt small"></td> - <td class="c023 small"></td> - </tr> - <tr> - <td class="c022 brt bbt small">1854</td> - <td class="c022 brt bbt small"></td> - <td class="c022 brd bbt small"></td> - <td class="c022 brt bbt small"></td> - <td class="c023 bbt small"></td> - </tr> - </tbody> -</table> - -<p class="c007 small">EDWARD YOUNG, <i>Chief of Bureau</i>. -</p> -<p class="small"><span class="smcap">Bureau of Statistics</span>, Nov. 16, 1872. -</p> - -<p class="c009"> -The extraordinary quantity imported in 1862, we hardly need remark, -was due to the demand for consumption in army cloths. Indigo imported -directly, was made free of duty in 1861. The duty which appears by the -above table to have been charged since that period, was upon indigo, -the product of India, imported by way of England, which was subject to -an extra duty of ten per cent. -</p> - -<p class="c009"> -The indigo consumed in the United States is generally supplied by the -Boston and New York Calcutta houses, who have either an American -partner resident in Calcutta, or who employ a resident American as -agent. Indigo, like other Calcutta goods, <span class="pagenum" id="Page_027">27</span> is sold through the agency -of brokers, who receive on this article a commission of one per cent. -The value of the article is known almost daily in these cities by -telegrams, giving exact information of the state of the trade, -transmitted from Calcutta as often as every five days. Some of the -brokers publish monthly circulars, showing the stock of indigo with -other Calcutta goods on hand in our market. The regular trade reports -issued by the India merchants show that The higher qualities of indigo -do not come to our market. The following is an extract from a report -of Whitney, Brother, & Co., of 1871:— -</p> - -<table class="table5" summary="US Imports"> - <tbody> - <tr> - <td class="c006 small">Indigo for Continent</td> - <td class="c037 small">fine</td> - <td class="c037 small">350 to 362</td> - <td class="c006 small">rupees.</td> - </tr> - <tr> - <td class="c038 small">„ „ „</td> - <td class="c037 small">good</td> - <td class="c037 small">330 „ 345</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">„ „ „</td> - <td class="c037 small">middling</td> - <td class="c037 small">310 „ 325</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">American consuming</td> - <td class="c037 small">fine</td> - <td class="c037 small">280 „ 300</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">„ „</td> - <td class="c037 small">good</td> - <td class="c037 small">250 „ 275</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">„ „</td> - <td class="c037 small">middling</td> - <td class="c037 small">200 „ 240</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">„ „</td> - <td class="c037 small">low and ordinary</td> - <td class="c037 small">150 „ 170</td> - <td class="c038 small">„</td> - </tr> - </tbody> -</table> - -<p class="c009"> -At the present moment there is great depression in the trade in this -article. The last telegrams show a decline of price in the Indian -trade in this article of from fifty to seventy-five per cent from the -prices of last year; and the apprehension is even entertained that -indigo is going out of use, the dreaded competitors being the aniline -dyes, and particularly the Nicholson blue. We maybe presumptuous in -giving our opinion on the question, but we hazard the prediction that, -notwithstanding the temporary popularity of the cheap substitutes, a -reaction will take place in favor of that “wonderful and most valuable -production,” whose importance as a dye has been held in India for -thousands of years and Europe for two centuries, “greatly to exceed -any other.”<a - id="FNanchor_2"></a> <a href="#Footnote_2" - class="fnanchor">[2]</a> -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_2"></a><a href="#FNanchor_2"> -<span class="label">[2]</span></a> -<p class="c009"> -The “Dictionnaire Universel du Commerce,” &c., published in -1861, contains an exhaustive article on the commerce in indigo, -by M. S. Beekrode. From the statements of this writer, it appears -that the consumption of indigo was estimated, in 1835, as follows:— -</p> - - -<table class="table5" summary="Indigo Consumption"> - <tbody> - <tr> - <td class="c006 small">Great Britain</td> - <td class="c007 small">1,214,380</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(2,683,779)</td> - <td class="c038 small">lbs.</td> - </tr> - <tr> - <td class="c006 small">France</td> - <td class="c007 small">912,915</td> - <td class="c038 small">„</td> - <td class="c007 small">(2,017,542)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">United States</td> - <td class="c007 small">130,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(277,300)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Other countries</td> - <td class="c007 bbt small">2,435,473</td> - <td class="c038 small">„</td> - <td class="c007 bbt small">(5,382,395)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">Total</td> - <td class="c007 small">4,692,768</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(10,362,016)</td> - <td class="c038 small">lbs.</td> - </tr> - </tbody> -</table> - - -<p class="c009"> -The approximate consumption in 1859 is stated as follows:— -</p> - -<table class="table5" summary="Indigo Consumption in 1859"> - <tbody> - <tr> - <td class="c006 small">Great Britain</td> - <td class="c007 small">800,000</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(1,768,000)</td> - <td class="c038 small">lbs.</td> - </tr> - <tr> - <td class="c006 small">France</td> - <td class="c007 small">800,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(1,768,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">United States</td> - <td class="c007 small">400,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(884,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Russia</td> - <td class="c007 small">860,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(1,900,600)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">The Zollverein</td> - <td class="c007 small">1,250,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(2,762,500)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Switzerland</td> - <td class="c007 small">150,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(331,500)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Austria</td> - <td class="c007 small">400,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(884,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Other countries</td> - <td class="c007 bbt small">300,000</td> - <td class="c038 small">„</td> - <td class="c007 bbt small">(663,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">Total</td> - <td class="c007 small">4,960,000</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(10,961,600)</td> - <td class="c038 small">lbs.</td> - </tr> - </tbody> -</table> - -<p class="c009"> -The average production in 1859 is estimated as follows:— -</p> - -<table class="table5" summary="Indigo Production estimate for 1859"> - <tbody> - <tr> - <td class="c006 small">Bengal, Madras, &c.</td> - <td class="c007 small">3,500,000</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(7,735,000)</td> - <td class="c038 small">lbs.</td> - </tr> - <tr> - <td class="c006 small">Java</td> - <td class="c007 small">550,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(1,215,500)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Central America</td> - <td class="c007 small">300,000</td> - <td class="c038 small">„</td> - <td class="c007 small">(884,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Other sources</td> - <td class="c007 bbt small">100,000</td> - <td class="c038 small">„</td> - <td class="c007 bbt small">(221,000)</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c038 small">Total</td> - <td class="c007 small">4,450,000</td> - <td class="c007 small">kilograms</td> - <td class="c007 small">(9,834,500)</td> - <td class="c038 small">lbs.</td> - </tr> - </tbody> -</table> - -<p class="small c009"> -As the maximum annual consumption in 1859 is set down at -5,000,000 kilograms, the author concludes that the average -production at that time did not surpass the requirements of the -dyers of the whole world. -</p> - -</div> - -<p><span class="pagenum" id="Page_028">28</span> -</p> - -<h3>FORMER PRODUCTION IN THE CAROLINAS.</h3> - -<p class="c009"> -As pertinent to the commercial branch of our subject, we must briefly -notice the remarkable facts of the sudden growth and equally sudden -and extraordinary extinction of the production of indigo in the -Carolinas. Indigo was for many years the second great staple of South -Carolina. So highly was this staple estimated that the historian of -the State declares that “it proved more really beneficial to Carolina -than the mines of Mexico or Peru are or ever have been to Old or New -Spain.” Its introduction was the happy result of a woman’s culture and -energy. In the early part of the last century, the indigo plant had -been extensively cultivated in the West India Islands, which then -furnished the chief supply of Europe. The governor of Antigua, George -Lucas, whose home plantation was at Wappoo in Carolina, having -observed the fondness of his daughter, Miss Eliza Lucas, afterwards -the mother of General Charles Cotesworth Pinckney, for the culture of -plants, was in the habit of sending to her tropical seeds to be sowed -on his plantation at Wappoo. Among others, he sent her some seeds of -the indigo plant cultivated in the West Indies. She planted them for -two years; but <span class="pagenum" id="Page_029">29</span> the seeds failed to germinate, or were killed by the -frost. On the third year’s trial, in 1741 or 1742, she was successful. -Governor Lucas, on hearing that the plants had ripened and produced -seed, sent from Montserrat a person skilled in making indigo. Vats -were built on Wappoo Creek, and there the first American indigo was -manufactured. The attempts of the expert to conceal his processes were -defeated by the vigilance of Miss Lucas. The process of manufacture -was made known. Seeds from the Wappoo plantation were freely -distributed and successfully planted; and the culture of indigo became -common. In 1747, a considerable quantity of indigo was sent to -England, which induced the merchants trading with Carolina to petition -parliament for a bounty on Carolina indigo. In 1748, an act of -parliament was passed granting a bounty of sixpence per pound on -indigo raised on British-American plantations and imported directly to -Britain from its place of growth. This act stimulated the planters of -Carolina to double vigor in the production of this new material for -export. “Many of them,” says Dr. Ramsay, “doubled their capital every -three or four years by planting indigo.” In the year 1754, the export -of indigo from the province amounted to 216,924 lbs., and in the years -1772 and 1773 the export had risen to 1,107,661 lbs. The production -was greatly checked by the war of the Revolution. Near the close of -the century the large importations from India lowered the price, so as -to make the planting unprofitable. In the mean time, the culture of -cotton had sprung up under the protective tariff of 1789. The grounds -suitable for indigo planting were equally fitted for cotton, and were -for the most planted with the new staple. It is curious to observe how -the former was displaced by the latter staple. The export of indigo -from Charleston in 1797 was 96,121 lbs.: in 1800, it fell to 3,400 -lbs. During the same years, the exports of cotton rose from one -million to six and a half million pounds. The production of American -indigo appears to have revived from time to time up to 1829. A writer -of that period in Silliman’s Journal of Science estimates—although it -would seem on doubtful authority—the production of indigo in the -United States at 20,000 lbs. The price <span class="pagenum" id="Page_030">30</span> of the American article had -fallen, owing to the great quantity of extractive which it contained, -to fifty cents per pound, while the Bengal indigo was worth $1.15 per -pound. We have no data as to its production at the present time, but -infer, from the fact that no reference has been made to this product -in the Government Agricultural Reports for many years past, that the -production, if any, is too unimportant to be noticed. -</p> - -<h3>INDUSTRIAL APPLICATION OF INDIGO.</h3> - -<p class="c009"> -All the applications of indigo require that the material should first -be reduced to an impalpable powder. It is better to grind it with -water, to prevent the loss of material in the form of powder, although -the dry pulverization is necessary when the indigo is to be used for -the manufacture of the sulphate. To facilitate the grinding the -material into a paste, it should be previously soaked in hot water -from one to three hours. The grinding on a small scale may be done by -a very simple apparatus. This is a hemispherical vessel of copper or -cast-iron, eighteen inches in diameter, furnished at the edge with two -handles. The workman, sitting astride a bench, places the vessel -before him, in which he places three heavy cast-iron balls, the indigo -which has been softened, and a sufficient quantity of water. Holding -the basin by the handles, he gives it a circular oscillatory movement, -in such a manner that the balls, following this movement, crush the -indigo which surrounds them; after which the contents are poured into -another vessel, water is added, and the material is stirred. The -portions incompletely ground are made to reunite themselves at the -bottom by means of regular blows with a hammer on the rim of the -vessel. The upper liquid is decanted, and the deposit is submitted to -a new manipulation in the basin. -</p> - -<p class="c009"> -In large establishments the grinding is done by machinery. An -apparatus highly recommended, consists of two circular plates of -cast-iron, arranged horizontally and slightly separated, one from the -other, which are rapidly rotated by power, in inverse, directions. The -interior surfaces of these disks are provided with deep grooves -radiating in a curved line from the <span class="pagenum" id="Page_031">31</span> centre to the circumference, and -diminishing in depth in the same direction. The indigo which has been -previously softened enters between the two plates by an opening in the -centre of the upper one, and escapes in a thin paste by the -circumference. -</p> - -<p class="c009"> -The application of indigo to the coloring of textile fabrics requires -the complete dissolving of the substance, for which the mechanical -division is only a preliminary. There are only two known means of -dissolving this substance: 1. By reduction; 2. By the action of -concentrated sulphuric acid. The first means allows indigotine to be -regenerated; and, when the dyeing is completed, it is pure indigotine -which adheres to the colored fibre. By the second means, or dissolving -by sulphuric acid, the coloring material enters into a new -combination, from which it can never be separated: it becomes a new -substance, endowed with new and special properties. -</p> - -<p class="c009"> -<i>The fixing of Indigotine by means of Reduction</i>.—In this method the -operator avails himself of one of the most remarkable qualities of -indigotine: this is the facility with which this body takes up -hydrogen, and becomes transformed into a colorless substance, which is -soluble in favor of alkaline or alkaline-earthy bases, and is -susceptible of reproducing indigotine by simple oxidation in contact -with air. This hydrogenized substance is called white indigo. Blue -indigo, or indigotine, is insoluble except by concentrated sulphuric -acid; and this insolubility gives it its superiority to all other blue -dyes. Not being soluble, it cannot, as blue indigo, attach itself to -the material to be dyed; but in the soluble form of white indigo it -can perfectly penetrate the fibre. If by any means of oxidation we can -transform the white indigo into blue indigotine, the latter becomes -insoluble, and is imprisoned in the pores of the fibre. This is, -briefly, the whole theory of the use of indigo in dyeing or printing, -although the reaction may be applied in different ways to the coloring -of fibres, such as— -</p> - -<p class="c009"> -1. The indigo is dissolved by means of an alkaline reduction in a vat, -and the fibre is immersed in the bath. This is the common blue vat. -</p> - -<p class="c009"> -2. The solution prepared beforehand is painted by a hair <span class="pagenum" id="Page_032">32</span> pencil and -printed by a stamp or roller upon only certain parts of the tissues. -This is the pencil blue. -</p> - -<p class="c009"> -3. The white indigo is precipitated under the form of a paste, in -combination with a metallic oxide having strong reducing power, such -as hydrated protoxide of tin, which prevents the too rapid reoxidation -of the indigotine. The thickened paste is printed, and the tissue is -placed in an alkaline bath (lime or soda), which, displacing the oxide -of tin, forms a soluble combination of white indigo. The latter can -then penetrate the fibre, and afterwards become fixed by reoxidation. -This is the printer’s solid blue. -</p> - -<p class="c009"> -4. The finely ground, but not dissolved indigo, is placed upon the -tissue in such conditions that it can be dissolved and reduced in -place. This done, the fixing of the indigotine is effected by -oxidation. This is the method for China blue or <i>bleu faïence</i>. -</p> - -<p class="c009"> -Without dwelling upon the details of these methods, we hasten to a -consideration of the most important of all the applications of indigo:— -</p> - -<h3>DYEING BY THE INDIGO VAT.</h3> - -<p class="c009"> -<i>The Copperas Vat</i>.—For dyeing cotton, the method of reduction found -by experience to be the most convenient and practical is founded upon -the action of the hydrate of the protoxide of iron in the presence of -lime. The hydrated protoxide of iron is obtained from sulphate of iron -(green vitriol, or copperas) with freshly burned lime. Certain -precautions should be observed in the use of these materials. The -copperas used for the preparation of these vats should be free from -sulphate of copper, because the oxide of copper which would be formed -in the vats rapidly oxidizes the reduced indigo, and causes its -precipitation in the bath. The copperas ought not to contain red oxide -of iron, nor sulphate of alumina. The coppery or oxidized vitriol may -be purified by boiling the solution with pieces of iron, which -precipitates the iron and neutralizes the oxide. The lime ought to be -pure, containing no magnesia; when slacked lime has been exposed to -the air, even for a short time, it absorbs carbonic acid, and becomes -converted into chalk. The lime, therefore, <span class="pagenum" id="Page_033">33</span> should always be newly -slacked. The ingredients, then, of a copperas vat are water, pure or -purified green vitriol, indigo ground into a homogeneous impalpable -paste, and pure and freshly slacked lime. The proportions used in -different establishments are exceedingly variable. Those which answer -for a laboratory vat, or a small vat used for precipitating the white -indigo immediately for printing, are: indigo, one part; sulphate of -iron, two parts; slacked lime, three parts. These proportions are not -enough for the large vats used in dyeing pieces. In them it is -necessary to make the quantities of lime and sulphate of iron larger -than the theory of the vat requires. The excess of lime and hydrate of -iron serve the purpose, whenever the vat is stirred, to repair the -losses of indigo caused by its oxidation from contact with the air. -Schutzenberger gives the proportions generally used by the dyers of -France, as follows:— -</p> - -<table class="table5" summary="Schutzenberger dye ratios 1"> - <tbody> - <tr> - <td class="c006 small">Indigo</td> - <td class="c006 small">1</td> - <td class="c007 small">part.</td> - </tr> - <tr> - <td class="c006 small">Crystallized sulphate of iron</td> - <td class="c006 small">3</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Freshly slacked lime</td> - <td class="c006 small">3</td> - <td class="c038 small">„</td> - </tr> - </tbody> -</table> - -<p> -Others, he says, use more lime than copperas, as in the following -proportion:— -</p> - -<table class="table5" summary="Schutzenberger dye ratios 2"> - <tbody> - <tr> - <td class="c006 small">Indigo</td> - <td class="c006 small">2</td> - <td class="c007 small">parts.</td> - </tr> - <tr> - <td class="c006 small">Sulphate of iron</td> - <td class="c006 small">5.5</td> - <td class="c038 small">„</td> - </tr> - <tr> - <td class="c006 small">Quicklime</td> - <td class="c006 small">6.5</td> - <td class="c038 small">„</td> - </tr> - </tbody> -</table> - -<p class="c009"> -M. de Kæppelin, who is especially familiar with the cotton dyeing in -Mulhouse, describes the ordinary vats for cotton dyeing as bound with -iron, and placed on the level of the ground. They hold from 3,000 to -4,000 litres (1,055 gallons) of liquid. In preparing them the dyer -fills them about three-quarters full of water, and pours in a milk of -lime, prepared with 45 kilograms (100 lbs.) of freshly slacked lime; a -fine liquid paste having been previously made from 15 kilograms (33 -lbs.) ground in water. This is added to the lime in the vat by -portions, the liquid in the vat being stirred up by a rake after each -portion of the indigo paste has been added. The indigo becomes -dissolved in about twenty-four hours, when the vat can be used. After -describing the manner in which the frame, or <i>champignon</i>, containing -the goods to be <span class="pagenum" id="Page_034">34</span> dyed is arranged and immersed in the vat, this author -continues: “It will be understood that the vat is composed according -to the degree of intensity of the color which is sought to be -obtained, and that hues more or less deep may be obtained by means of -more or fewer repeated immersions of the fabric to be dyed. After each -immersion the <i>champignon</i> is lifted out of the vat, and the fabrics -are left to <i>ungreen</i> themselves by contact with the air. (It must be -observed that, although soluble indigo is called white, because it is -without color when carefully prepared in the laboratory, the goods, -when first taken from the ordinary vat, are of a green color.) Exposed -to the air, the soluble indigo is precipitated in the state of blue -indigo upon the fibres of the tissue. This oxidation, or -<i>dehydryzation</i>, may be hastened by plunging the tissue into a vat -containing a solution, very much diluted with water, chloride of lime, -bichromate of potash, or sulphuric acid. The first two act as -oxidizing agents; the last facilitates the restoring of the blue -indigo by depriving it of the lime which is in excess in the solution -of indigo which the tissue has imbibed from the vat.” -</p> - -<p class="c009"> -He adds further: “To facilitate the formation of blue indigo in the -interior of the fabrics, the stuff to be dyed may be previously -impregnated by a saline solution, which has the property of -precipitating the white indigo from the alkaline solution, and of -fixing itself more rapidly upon the tissue. Oxide of copper and oxide -of manganese possess these properties in a high degree, and are used -in many establishments to hasten the dyeing process, and produce an -economy in raw materials. The pieces of cloth are placed in a solution -of sulphate of copper, in the proportion of 15 to 20 grams to the -litre (2.11 pints), and lightly thickened with starch. The fabrics, -thus impregnated by a kind of mordant, before receiving the blue dye -are first passed through a weak bath of milk of lime, which fixes the -oxide of copper upon the tissue. The blues thus obtained are more -intense, and have a peculiar lustre. This process is used in Austria -and Germany, where cotton fabrics are printed on both sides of the -tissue.” -</p> - -<p class="c009"> -Coming to the English authorities, Dr. Grace Calvert, in <span class="pagenum" id="Page_035">35</span> his recent -lectures before the Society of Arts, speaking of the cold vat for -dyeing cotton, says: “The oldest, and still most generally employed -method of preparing cold vats, consists of putting into a vat -containing about 2000 gallons of water 60 lbs. of indigo, very finely -powdered, 180 lbs. of slacked lime, and 120 lbs. of sulphate of -protoxide of iron, or green vitriol (free from any trace of copper -salt), the two latter substances being added from time to time. The -greater part of the lime used unites with the sulphuric acid of the -iron salt, to produce sulphate of lime or gypsum; and the liberated -protoxide of iron removes the oxygen from the indigo, becoming -converted into saline oxide, whilst the reduced indigo dissolves in -the excess of lime employed.” -</p> - -<p class="c009"> -He adds the following facts, which may be of practical -value:— -</p> - -<p class="c009"> -“Messrs. R. Schloesser & Co., of Manchester, have introduced within -the last year or two a marked improvement, in the preparation of cold -vats, which removes the great objections of the bulky precipitate of -sulphate of lime, the formation of an oxide of iron, and the loss of -indigo by its combination with the oxide of iron. The bath remaining -much more fluid, the pieces are less apt to be spotted, and a better -class of work is produced. To carry out their process, they add to the -ordinary 2,000 gallon vat 20 lbs. of ground indigo, 30 lbs. of iron -borings, 30 lbs. of <i>their remarkable powdered zinc</i>, and 35 lbs. of -quicklime; the whole is stirred up from time to time, for twenty-four -hours, when it is ready for use. If the bath is not considered -sufficiently strong, a little more lime and zinc are introduced. The -chemical theory of the process is, that the zinc, under the influence -of the lime, decomposes the water, combining with its oxygen, and the -hydrogen thus liberated removes oxygen from the indigo which then -dissolves in the lime.” -</p> - -<p class="c009"> -An excellent description of the processes employed at Manchester, -England, in preparing and working the copperas, or cold vat, is given -in Ure’s “Dictionary of Manufactures.” “The ingredients necessary for -setting the vat are copperas, newly slacked quicklime, and water. -Various proportions of <span class="pagenum" id="Page_036">36</span> these ingredients are employed, as, for -instance: 1 part by weight of indigo (dry), 3 parts of copperas, and 4 -of lime; or, 1 of indigo, 2¹⁄₂₃ of copperas, and 3 of lime; or, 8 of -indigo, 14 of copperas, and 20 of lime; or, 1 of indigo, ¾ of -copperas, and 20 of lime; or 1 of indigo, 4 of copperas, and 1 of -lime. The sulphate of iron should be as free as possible, from red -oxide of iron, as well as sulphate of copper, which reoxidize the -reduced indigo-blue. The vat, having been filled with water to near -the top, the materials are introduced, and the whole, after being well -stirred several times, is left to stand for about twelve hours. The -chemical action which takes place is very simple. The protoxide of -iron, which is set at liberty by the lime, reduces the indigo-blue; -and the indigo, which is then dissolved by the excess of lime, forming -a solution, which, on being examined in a glass, appears perfectly -transparent and of a pure yellow color, and becomes covered, whenever -it comes in contact with the air, with a copper-colored pellicle of -regenerated indigo-blue. The sediment at the bottom of the vat -consists of sulphate of lime, peroxide of iron, and the insoluble -impurities of the indigo, such as indigo-brown in combination with -lime, as well as sand, clay, &c. If an excess of lime is present, a -little reduced indigo-blue will also be found in the sediment in -combination with lime. The dyeing process itself is very simple. -The vat having been allowed to settle, the goods are plunged into the -clear liquor, and, after being moved about in it for some time, are -taken out, allowed to drain, and exposed to the action of the -atmosphere. While in the liquid, the fabric attracts a portion of the -reduced indigo-blue. On now removing it from the liquid, it appears -green, but soon becomes blue on exposure to the air, in consequence of -the oxidation of the reduced indigo-blue. On again plunging it into -the vat, the deoxidizing action of the vat does not again remove the -indigo-blue which has been deposited within and around the vegetable -or animal fibre, but, on the contrary, a fresh portion of the reduced -indigo-blue is attracted, which, on removal from the liquid, is again -oxidized like the first, and the color thus becomes a shade darker. By -repeating this process several <span class="pagenum" id="Page_037">37</span> times the requisite depth of color is -attained. This effect cannot, in any case, be produced by one -immersion in the vat, however strong it may be. The beauty of the -color is increased by finally passing the goods through diluted -sulphuric or muriatic acid, which removes the adhering lime and oxide -of iron. After being used for some time, the vat should be refreshed -or fed with copperas and lime, upon which occasion the sediment must -first be stirred up, and then allowed to settle again, so as to leave -the liquor clear. The indigo-blue, however, is in course of time -gradually removed, and by degrees the vat becomes capable of dyeing -only pale shades of blue. When the color produced by it is only very -faint, it is no longer worth while using it, and the contents are then -thrown away. In dyeing cotton with indigo, it seems to be essential -that the reduced indigo-blue should be in contact with lime. If potash -or soda are used in its place, it is impossible to obtain dark shades -of blue.” -</p> - -<h3>FERMENTING VATS FOR WOOL DYEING.</h3> - -<p class="c009"> -The application of indigo-blue to wool and woollen tissues is always -made by means of vats, which have special names; as, the pastel or -woad vat, the urine vat, German vat, molasses vat, &c. The reduction -or <i>hydrogenation</i> of the indigo-blue is the result of a peculiar -fermentation, which is developed within an alkaline liquor by means of -nitrogenized substances and bodies rich in sugar or hydrocarbonized -substances. It is known that in these conditions, especially where the -temperature is slightly raised, the sugar is converted into butyric -acid, and at the same time carbonic acid and hydrogen are set free. We -find here the source of the nascent hydrogen which fixes itself upon -the indigo-blue, and transforms it into white indigo, which is soluble -in the alkalies of the vat. It has recently been observed that the -butyric fermentation proceeds from the development of minute -infusoria. These animalculæ live without any supply of oxygen, and, in -fact, are killed in its presence. They therefore live at their ease in -the vat of reduced indigo, where no oxygen is permitted to enter. -</p> - -<p class="c009"> -The ingredients most usually employed for furnishing the <span class="pagenum" id="Page_038">38</span> -hydrocarbonaceous substances for fermentation are bran and ground -madder, although molasses is sometimes used. The nitrogenized material -is found in the woad or pastel, which is often added in very large -proportions to the fermenting vats. It is observed by the chemists who -have studied this subject most carefully, that the preparation of -vats, founded upon the principle of fermentation, does not repose upon -principles so sure and constant as those of the copperas vat, and that -many unforeseen accidents interpose to disturb the work of an -inexperienced dyer. The phenomena in fermentations are often complex. -It is admitted that in these phenomena theory has not said its last -word, and that empiricism is often more fortunate than science. In -conducting the operations of the warm fermenting vat, the conceit of -the practical dyer, so often remarked upon, is not without foundation. -By practical experience and the traditions of his art he has acquired -a knowledge of the almost insensible modification in conditions which -can change or arrest the chemical reaction. It is the knowledge of the -workman, a knowledge almost instinctive, which can never be -communicated to the books, and which is most respected by those most -profoundly informed in theory. -</p> - -<p class="c009"> -<i>The Woad or Pastel Vat</i>.—In former times woad, already referred to, -was the only material known to the dyers of Europe for producing the -blue color of indigo. For dyeing wool, the use of woad, now abandoned -wholly in cotton dyeing, has been retained to the present day, -generally for the purpose of exciting fermentation, and without regard -to its effect in imparting color to the material to be dyed; for the -woad grown in England, and used in the dye-houses of that country, -contains no trace of coloring matter. The woad, or pastel, grown in -the warmer districts of France contains about two per cent of -indigotine, which is regarded in that country as an important addition -to the coloring material, especially for improving the tone of the -color. Various substitutes, such as rhubarb leaves, turnip and carrot -tops, and weld, have been tried, but without advantage, with the -exception, perhaps, of weld, which is still used by some dyers. Some -chemists regard the use of woad as <span class="pagenum" id="Page_039">39</span> the remnant of a prejudice; but the -better opinion is, that this material possesses peculiar -fermentiscible qualities, whose exact action science has yet to resolve. -</p> - -<p class="c009"> -According to Schutzenberger, the most recent and highest French -authority, the dimensions of the pastel vat are about 6½ feet in -diameter, by 9 in depth. 100 kilograms (221 lbs.) of pastel, in balls, -is placed in the vat, which is then filled with boiling water. To this -is added 10 kilograms (22 lbs.) of madder, 3 to 4 kilograms (about 6½ -to 8¾ lbs.) of bran, and 4 kilograms of quicklime, which has been -slacked, and in the form of a <i>bouilli</i>. Sometimes weld is also added. -After three hours of rest, the vat is well raked, and the operation is -repeated every three hours. There is gradually developed a -characteristic ammoniacal vapor, and a blue scum, with veins of deeper -blue, forms on the surface; and the liquid, when agitated in the air, -rapidly becomes blue. These symptoms indicate the dissolution of the -indigotine of the woad; then there is added 10 kilograms (22 lbs.) of -indigo which has been previously ground in water, and the vat is -stirred. If the fermentation appears to be proceeding too actively, -which is recognized by the disengagement of gases, it is checked by -the addition of a proper dose of lime. On the other hand, the -fermentation is made more active by increasing the dose of bran. The -first dyes are not so good as those subsequently obtained, as the woad -absorbs from the bath certain brown or yellow materials, kept in -solution, and furnished as well by the pastel and madder as by the -indigo itself. 100 kilograms of wool require from 8 to 12 kilograms of -indigo. The vat is kept up by successive additions of indigo and lime, -made in the evening. -</p> - -<p class="c009"> -Another kind of pastel vat, prepared much like the last, receives an -addition of a dose of potash. M. de Kæppelin describes it as the one -at present in general use in France. Into a vat containing from 3,000 -to 4,000 litres (791 to 1,055 gallons) there is placed 75 kilograms -(166 lbs.) of pastel in loaves, or which has undergone a kind of -fermentation; or, what is preferable, 80 to 100 kilograms (176 to 221 -lbs.) of pastel or woad gathered without fermentation, and 10 -kilograms (22 lbs.) of <span class="pagenum" id="Page_040">40</span> indigo, ground to a paste with water. This -mixture is well stirred, and there is added 4 kilograms (about 9 lbs.) -of Avignon madder, and the same quantity of carbonate of potash. After -the vat has been well raked there is added 2 kilograms (4½ lbs.) of -slacked lime, and some pails of bran. The vat is well covered, either -with a wooden lid, or woollen cloths. The fermentation is allowed to -proceed, and after five or six hours the vat is uncovered and raked -with much care for half an hour. This operation is repeated every -three hours, until it is recognized that the indigo is well dissolved. -In this case the bath ought to be of a beautiful yellow color, and be -covered with a light blue irised film, veined with yellow at the least -movement given to the liquid. If the fermentation proceeds too -rapidly, a little lime is added to moderate it. -</p> - -<p class="c009"> -For keeping up a vat like this, and to obviate the different -inconveniences to which it is subject, the dyer sometimes adds lime, -or sugar, and carbonate of ammonia, sometimes madder, or bran, or even -tartar-lees. These last additions are made to saturate the excess of -lime which the vat contains. In this case the yellow veins and the -beautiful blue scum which cover the surface disappear, or become pale; -a piquant odor is disengaged, and the liquor becomes blackish. When -lime or sugar are added, it is for the purpose of retarding the -fermentation of the woad. Sugar might even entirely take the place of -pastel for effecting the reduction of the indigo, and many -establishments in France are commencing to use it for this purpose. A -good vat, well supplied with successive additions of indigo, pastel, -bran, and madder, in proportions necessary to effect and prolong the -fermentation necessary for the dissolution of the indigo, may be kept -up many years. -</p> - -<p class="c009"> -Schutzenberger observes that the vats of fermentation are subject to -certain maladies, the two most frequent of which are due, one to an -excess, and the other to an insufficient quantity of lime. “In the -first case, the liquid takes a tint more and more free of color, loses -its <i>fleurée</i> (surface scum) and odor; the fermentation is then -arrested by the precipitation of the active matters. This -inconvenience is remedied, if seen in time, by <span class="pagenum" id="Page_041">41</span> adding sulphate of -iron, which eliminates the too great excess of lime. In the second, -the fermentation becomes too active, passes into a putrid -fermentation, and the liquid assumes a reddish tint; a fabric dyed -with indigo in this state becomes very soon discolored. The sole means -of safety is to heat the bath up to 90° and to add lime. If this does -not accomplish the purpose of arresting the putrefaction the vat is -lost.” -</p> - -<p class="c009"> -The following account of the method of dyeing woollen goods with -indigo by means of the woad vat is given by Dr. Ure, as that carried -on in Yorkshire, the great centre of the woollen manufacture of England. -</p> - -<p class="c009"> -“The dye-vats employed are circular, having a diameter of six feet six -inches, and depth of seven feet, and are made of cast-iron -five-eighths of an inch in thickness. They are surrounded by -brickwork, a space of three inches in width being left between the -brickwork and the iron, for the purpose of admitting steam, by means -of which the vats are heated. The interior surface of the brickwork is -well cemented. In setting a vat the following materials are used: 5 -cwt. of woad, 30 lbs. of indigo, 56 lbs. of bran, 7 lbs. of madder, 10 -quarts of lime. The woad supplied to the Yorkshire dyers is grown and -prepared in Lincolnshire. It is in the form of a thick, brownish -yellow paste, having a strong ammoniacal smell. The indigo is ground -with water in the usual manner. The madder acts in promoting -fermentation, but it also serves to give a reddish tinge to the color. -The lime is prepared by putting quicklime into a basket, then dipping -it in water for an instant, lifting it out again, and then passing it -through a sieve, by which means it is reduced to a fine powder, called -by the dyers <i>ware</i>. The vat is first filled with water, which is -heated to 140° F., after which the materials are put in, and the whole -is well stirred until the woad is dissolved or diffused, and it is -then left to stand undisturbed overnight; at six o’clock the next -morning the liquor is again stirred up, and five quarts more of lime -are added; at ten o’clock five pints of lime are again thrown in, and -at twelve o’clock the heat is raised to 120° F., which temperature -must be kept up until three o’clock, when another quart of lime <span class="pagenum" id="Page_042">42</span> is -introduced. The vat is now ready for dyeing. When the process of -fermentation is proceeding in a regular manner, the liquid, though -muddy from insoluble vegetable matter in suspension, is of a yellow or -olive yellow color; its surface is covered with a blue froth or -copper-colored pellicle, and it exhales a peculiar ammoniacal odor; at -the bottom of the vat there is a mass of undissolved, matter of a -dirty yellow color. If there is an excess of lime present, the liquor -has a dark green color, and is covered with a grayish film, and, when -agitated, the bubbles which are formed agglomerate on the surface, and -are not easily broken. Cloth dyed in a liquid of this kind loses its -color on being washed. This state of the vat is remedied by the -addition of bran, and is of no serious consequence. When, on the other -hand, there is a deficiency of lime, or, in other words, when the -fermentation is too active, the liquor acquires first a drab, then a -clay-like color; when agitated, the bubbles which form on its surface -burst easily, and when stirred up from the bottom with a rake it -effervesces slightly, or <i>frits</i>, as the dyers say. If the -fermentation be not checked at this stage, putrefaction soon sets in, -the liquid begins to exhale a fetid odor, and when stirred evolves -large quantities of gas, which burns with a blue flame on the -application of a light. The indigo is now totally destroyed, and the -contents of the vat may be thrown away. No further addition of woad is -required after the introduction of the quantity taken in first setting -the vat, the fermentation being kept up by adding daily about four -pounds of bran with one quart or three quarts of lime. Indigo is also -added daily for about three or four months. The vat is then used for -the purpose of dyeing light shades, until the indigo contained in it -is quite exhausted, and its contents are then thrown away.” -</p> - -<p class="c009"> -This author adds: “Woollen cloth, before being dyed, is boiled in -water for one hour, then passed immediately under cold water. If it be -suffered to lie in heaps after being boiled it undergoes some change, -which renders it afterwards incapable of taking up color in the vat. -In dyeing, the cloth is placed on a net-work of rope attached to an -iron ring, which is suspended by four iron chains to a depth of about -three feet beneath the surface of the <span class="pagenum" id="Page_043">43</span> liquor. The cloth is stirred -about in the liquor by means of hooks for about twenty or thirty -minutes. It is then taken out and well wrung. It now appears green, -but, on being unfolded and exposed to the air, rapidly becomes blue. -When the vat has an excess of lime the cloth has a dark green color -when taken out. It is then passed through hot water, and dipped again -if a darker shade is required.” -</p> - -<p class="c009"> -<i>The Indian Vat</i>.—This presents much analogy to the woad vat, as the -fermentation of vegetable matters effects the transformation of the -indigo-blue. According to Dr. Calvert, the Indian vat, probably so -called from its origin in the East, is taking the place in England of -the old woad vat for dyeing wool and woollens. He describes its -preparation as follows: 8 lbs. of powdered indigo is added to a bath -containing 3½ lbs. of bran, 3½ lbs. of madder, and 12 lbs. of potash, -which is maintained for several hours at a temperature of 200° F. It -is then allowed to cool to 100° F., when fermentation ensues. After -about forty-eight hours the indigo is rendered soluble, being reduced -by the decomposition of the sugar and other products contained in the -bran and the madder root during the process of fermentation. The -distinguishing feature of this vat is the use of <i>potash</i>. The Indian -or potash vats are spoken of by the best authorities as more easy to -manage than the woad vat. They are less subject to accidents, and -yield their coloring material more readily to the fibre, while three -times as much wool can be dyed in the same time. On the other hand, -they do not last so long, and require to be renewed at the end of -twenty-five or thirty days. Besides, the fibres dyed in the potash vat -have a darker shade than those dyed in the woad vat, owing to the -large quantity of the coloring matter of the madder dissolved by the -potash, which becomes fixed on the stuff with the indigo-blue. -</p> - -<p class="c009"> -<i>The Urine Vat</i>, but little used except for domestic dyeing, is founded -upon the same principles as the other fermenting vats. This excretion, -when putrefied, contains at the same time the nitrogenized principles -which work as ferments and the alkali in the form of ammonia necessary -for dissolving the indigo. -</p> - -<p class="c009"> -According to Dr. Calvert, improvements have been made of <span class="pagenum" id="Page_044">44</span> late years in -the fermenting indigo vats by which the expense of madder is avoided. -They are now prepared by adding to water, at a temperature of 200° F., -2 buckets of bran, 26 lbs. of soda crystals, 12 lbs. of indigo, and 5 -lbs. of slacked lime. After five hours the bath is allowed to cool to -100° F., when fermentation ensues, and the indigo is dissolved in the -alkali. This is, in fact, the German vat, soda taking the place of the -potash, and the only fermenting material consisting of bran. -</p> - -<p class="c009"> -<i>The German Vat</i> is largely used by the dyers in the north of France, -and is considered as more advantageous than the Indian vat, because -the employment of soda is more economical than that of potash, while -the vat can be maintained as long as two years. The vats used by them -are prepared as follows: The water is heated to a temperature of 95°, -and receives 20 pails of bran, 11 kilograms (about 24 lbs.) of -crystals of carbonate of soda, 5.5 kilograms (11 lbs.) of indigo, and -4½ lbs. of slacked lime. After twelve hours, the temperature having -been kept at 40° or 50°, fermentation commences, the liquid becomes of -a greenish blue color, and disengages bubbles of gas. Indigo, soda, -and lime are put in from time to time in the proportions above -indicated, and also from six to eight pounds of molasses. At the end -of the third day the vat is fit for use. -</p> - -<p class="c009"> -M. de Kæppelin, writing in. 1864, informs us that the reduction of -indigo by means of molasses, is at present largely employed in the -great establishments for dyeing woollen cloth at Sedan, Louviers, and -Elbœuf. -</p> - -<p class="c009"> -The vat used is of very large dimensions, and from twenty-two to -twenty-six pounds of indigo are dissolved in it; an equal weight of -molasses is used, and three or four times the same weight of potash -made caustic by a proportionate addition of lime. -</p> - -<p class="c009 c040"> -The space reserved for this subject in our present paper will not -permit us to enter upon a description of the processes used in the -American dye-houses. This, as well as the applications of indigo in -printing, and the uses of sulphate of indigo, must be deferred to -another number. -</p> - -<p class="c009"> -Let us, in concluding the first part of our paper, at the risk of <span class="pagenum" id="Page_045">45</span> -repetition, bring out in bolder relief a statement which presents the -philosophy of all the various processes of the indigo vat, and at the -same time, a conclusive argument for the use of this material, in -preference to all cheaper substitutes. Indigo cannot enter into a -fibre until it is dissolved. It cannot be dissolved so long as it is -in a blue state. When reduced by any of the processes above described -to the white state, it is easily dissolved, and can enter the pores of -the fibre. Upon exposure to the oxygen of the air it takes up an -equivalent of oxygen; it returns to the blue state, and, being then -insoluble, it cannot be washed away from the fabric, and being -saturated with oxygen it cannot be changed by air or light. This -theory of the application of indigo involves a lesson to -manufacturers, dealers, and consumers, especially of woollen fabrics. -The theory, as well as experience, dating back to the dawn of the -textile arts in the East, establishes that this material is -incalculably superior to any other, in permanence at least, for -imparting to woollen fibre a blue color, or as a foundation for most -of the darker colors. By far the largest proportion of all cloths are -of dark colors,—blue, black, green, brown, gray, or mixed,—and can -advantageously receive in all or a portion of the fibre constituting -them a direct dye or bottom for other dyes from indigo. It may be -safely stated that, as a whole, no cloths in the world are -manufactured from such good wool as those produced in the United -States. We might expect that the shoddy goods of Yorkshire should be -further falsified by fugacious dyes; but is it not a shame that our -admirable wool should be deprived of half its value by parsimony in -dyeing? The slightest shortcomings in dyeing are revealed in wear. The -writer cannot forbear referring to an illustration directly before his -eyes. He is wearing a garment, reduced now to the retired service of -an office coat, made of an admirable cheviot cloth of American -manufacture. The cloth originally was selected not only for its -excellent texture, but as an illustration of philosophical principles -applied in the formation of color. The tissue was made by weaving -three yarns of distinct colors,—blue, yellow, and red. Either of those -hues alone would have been <span class="pagenum" id="Page_046">46</span> glaring and conspicuous, but, by the law of -color, the combination of blue, red, and yellow makes black, and the -new cloth at a distance had the effect of a dark mixture. Upon -exposure to ordinary wear, the yellow and red have retained their -pristine hues; the blue, not being indigo dyed, has faded; and the -original dark mixture, although sound in fabric, has become of a -yellowish brown. The extra expense of a permanent dyeing material -forms so small a proportion of the whole cost of a finished garment, -that it ought not to be generally spared. The reform cannot be made by -the manufacturers; it must be made by the dealers, and especially by -that class of producers which has risen in our day into such great -importance,—the manufacturers of ready-made clothing. If they would -demand of the manufacturers, and furnish to their customers cloths -more permanently dyed, it would be another step in the direction to -which these establishments are tending,—the supply of the chief -portion of the woollen clothing of the people. The manufacturers would -gladly aid them; for it is the growing sentiment of American -manufacturers that all their productions should be, in the proverbial -phrase adopted from the dye-house, as expressing the highest -excellence,—<i>true blue</i>. -</p> - -<div class="no_pg_break"> -<p><span class="pagenum" id="Page_047">47</span> -</p> - -<h3>BIBLIOGRAPHY.</h3> - -<div class="c039"> -<p class="c009"> -Citations of authorities having been but partially made in the -preceding article, the writer, for the purpose of giving his sources -of information, and for the convenience of those who wish to pursue -the subject further, appends a list of the more important works which -he has consulted:— -</p> - -<p class="c009"> -Schutzenberger’s Traité des Matières Colorantes, t. ii. (the most -recent and best modern authority); Bancroft’s Philosophy of -Permanent Colors, vol. i.; Edinburgh Encyclopædia; Berzelius, -Traité de Chimie, t. vi; Chevrueil, Leçons de Chimie Appliquée à -Teinture, t. iii.; Dumas, Chimie Appliquée aux Arts, t. viii; -Wurtz, Dictionnaire de Chimie, 1872, art. Indigo; Indigo et son -Emploi, par De Kæppelin; Annales du Génie Civil, 1864, t. iii.; -Lectures of Dr. Grace Calvert, Chemical News, Aug. 9 and 23, 1872; -O’Neill’s Dictionary of Dyeing and Printing; Napier’s Chemistry -Adapted to Dyeing; Muspratt’s Chemistry Applied to the Arts, -articles Indigo and Dyeing; Ure’s Dictionary of Manufactures, ed. -of 1860; Proceedings of Royal Society, vol. xvi.; Proceedings of -Literary and Philosophic Society of Manchester, vol. iv.; McCulloch’s -Dictionary of Commerce, ed. 1869; Dictionnaire Universel du -Commerce, &c., ed. 1861; <i>South Carolina Production</i>.—Ramsay’s -History; Drayton’s South Carolina; Silliman’s Journal, vol. xviii. -A more complete bibliography is given in Schutzenberger’s work. -</p> -</div> -</div> - -<div class="section"> -<p><span class="pagenum" id="Page_049">49</span> -</p> -<p class="c008 large">PART II. -</p> - -<p><span class="pagenum" id="Page_051">51</span> -</p> -<h2 class="nobreak">PART II.</h2> -<hr class="short" /> -</div> - -<p> -<span class="smcap">We</span> entered upon the subject of indigo, which we have treated at some -length in our last issue, as much in the interest of the people as of -manufacturers, for we were deeply impressed with the conviction that -no improvement in our manufacturing processes would confer more -benefit upon the masses than imparting stability of color to the -clothing of the people. When one has a deep conviction upon a subject, -upon which others have equal opportunities for judging, he may be sure -that he is not alone in his impressions. He is moved by one of those -waves of thought which, operating simultaneously upon many minds, -gives that uniformity to public opinion at which we so often wonder. -We are gratified to find, from responses to our last article, that we -are not alone in our conviction of the importance of reviving “true -blue” dyes. The head of a mercantile house, the extent of whose -<i>clientèle</i> in mills both of wool and cotton is hardly surpassed, has -assured us that we have not overstated the reform in dyeing which we -have advocated. He had long shared in our convictions. Pointing to the -throng of men in the crowded street, where we were conversing, he -remarked that there was hardly a man in the crowd whose clothing would -not have been improved by indigo dye. “The failure to use indigo -dyes,” he <span class="pagenum" id="Page_052">52</span> emphatically said, “costs the laboring people of this -country millions of dollars every year. The fault is not to be charged -to our own manufacturers alone; for the blue coat which I wear, and -which I bought in Paris, annoys me by the crocking caused by its -aniline dye.” In one very large mill of which he is director as well -as selling agent, he is putting his principles in practice. All the -heavy blue cloths intended for popular consumption are faithfully -dyed, and each bears a stamp, “Warranted indigo dyed.” The ready-made -clothing establishments which largely consume these goods have already -found their advantage in purchasing them, and a similar stamp is -attached to each article made from this cloth. -</p> - -<p class="c009"> -Some of our most celebrated cotton fabrics have won and still retain -their reputation by the use of indigo dyes. The ginghams are a signal -illustration. The blue check is formed by weaving cotton yarns dyed -blue in the cold indigo vat with undyed yarns. These goods can be -washed indefinitely without change. -</p> - -<p class="c009"> -Another illustration is the famous A.B.A. Amoskeag tickings, -an article of such excellence that the question of the right to -use trade-mark A.B.A. gave rise to the leading American case -in this branch of law.<a - id="FNanchor_3"></a> <a href="#Footnote_3" - class="fnanchor">[3]</a> A prominent feature in these goods was and still is -the permanence of the dye in the blue stripe, produced by the cold -indigo vat. Still another illustration is the blue and white “shirting -stripe” first made by Mr. Samuel Batchelder, at the Hamilton Mills, -now so generally adopted for sailors’ shirts. The indigo dye enables -the color to resist the roughest possible usage. -</p> - -<p class="c009"> -To recur to the application of indigo dyeing to wool and woollens. We -have been unable, although we have written more than fifty letters of -inquiry upon the subject, to learn of any peculiarity or improvements -in the American processes of wool dyeing with indigo.<a - id="FNanchor_4"></a> <a href="#Footnote_4" - class="fnanchor">[4]</a> Our dyers are -for the most part <span class="pagenum" id="Page_053">53</span> foreigners. For this reason, or because the art of -indigo dyeing has long since reached perfection in the best -establishments abroad, they rigidly pursue the old European methods. -The best dyers regard the successful management of the warm fermenting -vats for wool as the highest test of their art. We have already spoken -of the complicity of the phenomena in fermentations. Practical dyers -endow the fermenting vat with a sort of personality. “An indigo vat,” -says one to us, “is more like a sick man than any thing in the world: -you have to watch it as you would a sick patient, and give it physic -or ferments to stir up the system and purify it.”<a - id="FNanchor_5"></a> <a href="#Footnote_5" - class="fnanchor">[5]</a> The diagnosis of -a sick vat requires that sort of instinctive knowledge which -experience gives to the practised physician. The impatience of our -young Americans will not permit them to serve the long apprenticeship -necessary to acquire the proper experience. The artisans not -thoroughly trained will naturally prefer the dyes and processes -introduced by modern science, which require but little skill in their -application. It is a curious fact that the influence of the national -government has been largely instrumental in preserving the old system -of indigo dyeing. Thanks to the Quartermaster-General’s Bureau, or the -man of science, General Meigs, who presides over it, indigo dyed -cloths have been persistently insisted upon for the army. The late war -gave a new impulse to indigo dyeing. A skilled dyer, whom we have -consulted, was constantly employed in Connecticut, on a tour of -professional inspection of a dozen or more different establishments -making army goods. No doctor, he says, ever found in hospital practice -more complications of disease than he found in the -<span class="pagenum" id="Page_054">54</span> ailing vats. Among -other difficulties there was a deficiency of imported woads, although -the cultivation of excellent woad immediately sprung up in -Connecticut. In the mean time carrot and rhubarb tops were used as -substitutes for the fermenting material of the woad. Carrot-tops grown -expressly for that purpose brought as high as twenty-five cents per -pound. Since the war the requisitions for indigo dyed woollen goods -have not relaxed, and the art is not likely to be lost. -</p> - -<p class="c009"> -With the real difficulties which attend the process, it is hard for -indigo dyeing to sustain itself in the face of cheap substitutes of -easy application, such as the Nicholson blue. It is exceedingly -difficult to piece dye with indigo and preserve a uniform hue upon the -cloth. Hence indigo dyes are generally given in the wool. The wool -absorbing the foreign material of the dye is more difficult to work in -the operations of carding and spining. In other words, a finer and -costlier wool is required. A great <i>desideratum</i> therefore is a means -of piece dyeing with indigo so as to preserve a perfect uniformity of -hue throughout the piece. This, we are happy to say, has been recently -successfully accomplished by one of the largest and most faithful of -our cloth-making establishments. It would be premature, before the -patents are secured for this invention, to explain the ingenious and -expensive apparatus devised for this purpose, which constitutes in -fact a battery of vats so arranged that the operation may be -continuous. The experiments authorize the statement that bottom dyes -of indigo, so desirable for a great variety of colors, can be applied -with no other additional cost than that of the dyeing material. When -this establishment, as it proposes, stamps upon the cards which -designate goods, already so admirable in material and texture, -“Warranted indigo dyed,” we shall regard it as an era in the American -card-wool manufacture. -</p> - -<p class="c009"> -The old European woad vat process is that used in all our -establishments. Mr. Henderson of the Washington Mills, whose -experience as a practical dyer of wool is exceptionally large, informs -us that he has found no work so instructive upon this process as -Napier’s “Chemistry of Dyeing” (published by Henry <span class="pagenum" id="Page_055">55</span> Carey Baird, of -Philadelphia, 1869). Napier’s description of the process is extracted -from Dumas’s “Lectures on Dyeing.” The appreciation expressed by so -competent a judge induces us to reprint Dumas’s description in an -appendix to this article. -</p> - -<p class="c009"> -That we may give at least a general view of the whole subject, we will -proceed to consider indigo in some relations not yet adverted to. -</p> - -<p class="c009"> -In Part I. of our notes we have treated only of the application of -this substance in dyeing by means of reduction through the indigo vat. -Indigo may be applied by means of reduction in the printing of -fabrics, as well as in dyeing them. A true scientific arrangement -would compel us next in order to consider this other application of -indigo by means of reduction. But the more natural and practical order -is to pursue the subject of dyeing, and to consider next the -applications of the derivatives from indigo in dyeing proper. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_3"></a><a href="#FNanchor_3"> -<span class="label">[3]</span></a> -<p class="c009"> -See the case stated at length in our article on Trade-marks, -Bulletin, vol. i. p. 102. -</p> -</div> - -<div class="footnote"> -<a id="Footnote_4"></a><a href="#FNanchor_4"> -<span class="label">[4]</span></a> -<p class="c009"> -A reply by Mr. D. R. Whitney, an extensive indigo importer, -to a letter of inquiry, enables us to correct some errors in our -former article, under the head of “commerce in indigo.” The value -of export from India in 1862–63, stated in dollars, through a -typographical error, should have been pounds sterling; thus, -instead of $2,126,814, read £2,126,814. It is stated in our first -article that the telegrams show a decline of price of indigo in -the Indian trade of from 50 to 75 per cent; “per cent” should -read “rupees,” which would make a decline of from 25 to 30 per -cent. The reason for the decline, as stated by Mr. Whitney, is -the unusually large crop of this year. The average crop of indigo -in Bengal is about 100,000 maunds. The crop of this year is -135,000 maunds, about 30 to 35 per cent above the average. -</p> - -<p class="c009"> -According to Mr. Whitney, the consumption of Bengal indigo in the -United States was 2,458 cases of 270 lbs. to a case on an -average, in 1871; and in 1872, 1,802 cases. Guatemala indigo, -3,132 serroons in 1871, and 2,578 serroons in 1872. -</p> -</div> - -<div class="footnote"> -<a id="Footnote_5"></a><a href="#FNanchor_5"> -<span class="label">[5]</span></a> -<p class="c009"> -See notes on “sickness” of vats in Appendix. -</p> -</div> - -<h3>SULPHURIC DERIVATIVES,—SAXON BLUE, &C.</h3> - -<p class="c009"> -The powerful action of sulphuric acid upon indigo, and the bright and -lively blue color thereby produced, had been observed by chemists long -ago; but no person appears to have applied this color upon cloth, -until it was done about the year 1740, by Counsellor Barth, at -Grossenhein, in Saxony. The vividness of the dye, and the facility -with which it was applied, brought it into great vogue under the name -of Saxon blue, from its origin. Its popularity in former times is -evinced by the words of the old song, “The Blue Bells of Scotland:”— -</p> - -<div class="poetry-container"> -<div class="poetry"> -<div class="stanza"> -<div class="verse small">“In what clothes, in what clothes is your Highland laddie clad?</div> -<div class="verse small">His bonnet’s of the <i>Saxon blue</i>, his waistcoat of the plaid.”<a - id="FNanchor_6"></a> <a href="#Footnote_6" - class="fnanchor">[6]</a></div> -</div> -</div> -</div> - -<p class="c009"> -The Saxon blue consists simply of a solution of indigo, the Guatemala -blue indigo being preferred, in sulphuric acid suitably diluted with -water. The result of this reaction is not a single chemical substance, -but two acids giving different tints, one called <i>sulpho-purpuric</i> -acid or <i>phenicine</i>, and the other <i>sulpho-indigotic</i> acid; the first -giving to wool a reddish-violet <span class="pagenum" id="Page_056">56</span> color, and the other a pure blue. A -third compound has been indicated by Berzelius, the nature of which -has not been determined. Whether one or the other of the two named -acids, or the two combined, shall be produced by the reaction between -the sulphuric acid and the indigo, depends upon the duration of the -contact, the temperature of the mixture, and the nature and proportion -of the acid used. -</p> - -<p class="c009"> -Persoz gives the following general receipt:— -</p> - -<table class="table5" summary="Persoz mixture ratios"> - <tbody> - <tr> - <td class="c006 small">1</td> - <td class="c006 small">part by weight of</td> - <td class="c006 small">indigo, finely rubbed.</td> - </tr> - <tr> - <td class="c006 small">1</td> - <td class="c038 small">„ „ „ „</td> - <td class="c006 small">Nordhaussen acid.</td> - </tr> - <tr> - <td class="c006 small">1</td> - <td class="c038 small">„ „ „ „</td> - <td class="c006 small">ordinary sulphuric acid.</td> - </tr> - </tbody> -</table> - -<p class="c009"> -Leave for forty-eight hours, then heat until a drop turned into -water will dissolve without producing a precipitate. Leave to -cool, and dilute with water till the strength is brought to 18 -Beaumé.” -</p> - -<p class="c009"> -Napier says that he has found the following method of preparing -sulphate of indigo, in quantities for use, very satisfactory: “The -indigo is reduced to an impalpable powder, and completely dried by -placing it on a sand bath or flue for some hours at a temperature of -about 150° F. For each pound of indigo six pounds of highly -concentrated sulphuric acid are put into a large jar, or earthen pot, -furnished with a cover. This is kept in as dry a place as possible, -and the indigo is added gradually in small quantities. The vessel is -kept closely covered, and care taken that the heat of the solution -does not exceed 212°F. When the indigo is all added, the vessel is -placed in such a situation that the heat may be kept up at about -150°F., and allowed to stand, stirring occasionally, for forty-eight -hours. These precautions being attended to, we have uniformly found -that any failure occurring was clearly traceable to the impurity of -the indigo or weakness of the acid used.” -</p> - -<p class="c009"> -The processes for producing and separating the two acids derived from -the combination of sulphur and indigo are minutely given by Berzelius, -in vol. i. of his “Traité de Chemie,” who states this curious fact -illustrative of the peculiar affinities of wool with certain dyeing -substances. Wool or flannel thoroughly scoured, when immersed in the -blue solution of indigo with <span class="pagenum" id="Page_057">57</span> sulphuric acid, acts as a base: it -combines gradually with the acid blue, and becomes itself colored of a -deep blue. When saturated with color, it is withdrawn. Fresh wool is -introduced until the bath yields no more color. If sublimed or -perfectly pure indigo is used, there remains in the bath nothing but -free sulphuric acid. The wool thus plays the part of a base with which -the blue acids combine. The dyed wool is afterwards washed and treated -in feeble alkaline bath (ammonia), which redissolves the blue. This -method of purifying the Saxon blue is still practised by French -manufacturers. -</p> - -<p class="c009"> -The combination of indigo with sulphuric acid, sometimes improperly -called sulphate of indigo, is known by the dyers here and in England -under the name of <i>chemic</i>. The name of <i>chemic</i> blue or green is also -given the dyes formed from the indigo extract hereafter spoken of. It -is largely used for making certain greens required in Scotch plaids. -</p> - -<p class="c009"> -The old Saxon blue or simple solution of indigo with sulphuric acid is -now seldom prepared by the manufacturers themselves. It is now -generally prepared for them, and furnished commercially under the name -of <i>indigo extract</i>. The finer qualities used for fine dyeing and -printing are known under the name of <i>carmines</i> of indigo, <i>neutral -extract</i>, <i>soluble indigo</i>, <i>ceruline</i>, &c. -</p> - -<p class="c009"> -The production of indigo carmines, which are simply alkaline -sulphindigotates or sulpho-purpurates, is founded upon their -insolubility in a liquid charged with a salt. -</p> - -<p class="c009"> -If, for example, we dissolve one part of indigo in four parts of -fuming acid, and dilute the liquid with sixty or eighty times its -weight of water, it will contain, besides the <i>sulphindigotic</i> acid, -an excess of sulphuric acid. By adding one part of crystals of soda so -as to neutralize the bath, there will be formed not only -sulphindigotate of soda, but sulphate of soda: as the former is -insoluble in the saline liquid, the presence of the sulphate of soda -causes the precipitation of the sulphindigotate in deep blue -floccules. These are collected on woollen filters and washed to remove -the sulphate of soda and a green coloring material, probably a -modified chlorophyl, which the paste often contains, and which has the -singular property of fixing itself on silk, but not on wool. -</p> - -<p><span class="pagenum" id="Page_058">58</span> -</p> - -<p class="c009"> -The carmines are divided according to their richness in indigo into -simple carmine (4.96 per cent of indigo, water 89, saline materials -57), double carmine (10.2 per cent indigo, water 85, salts 4–8), -triple carmine (12.4 per cent indigo water, 73.7, salts 13.9). A -species of solid carmine known as Boiley blue or purple is in high -repute in France. -</p> - -<p class="c009"> -The carmines may be tested by dyeing a specimen of wool in an -acidulated bath to which cream of tartar has been added. The presence -of the green matter, so objectionable to silk-dyers who make much use -of these carmines, is detected by rubbing a small quantity of the -carmine on a piece of glazed paper, which, when the color dries, gives -a color varying from blue to a rich copper color: if any green -coloring matter is left, it shows itself by a green aureola around the -blue color. The method of applying the carmines in dyeing wool and -silk,—for they are not adapted to cotton fabrics,—as given by M. de -Kæppelin, is as follows:— -</p> - -<p> -The operation is conducted in small wooden vats, provided with -openings for manipulation, and pipes for inducting steam to heat the -baths to the proper temperature. It consists of two parts, that of -mordanting and dyeing. The former is thus conducted. -</p> - -<p class="c009"> -For each kilogram of tissue which has been previously scoured and -bleached, there are provided 200 grammes of cream of tartar and 250 -grammes of alum. These are dissolved in the bath of water of the vat, -the temperature is raised to boiling heat, and the tissue is immersed -in the bath f of an hour while it is worked over through the opening -for manipulation. The pieces are then taken from the bath, to which is -added a solution of the carmine in water containing a quantity of -coloring matter proportionate to the intensity of the blue sought for. -The solution ought to be prepared with care and passed through a silk -sieve, so that the small insoluble grains which might have been left -through bad fabrication may be left on the sieve. After the pieces -have been manipulated in the colored bath, so as to exhaust the color -and obtain the required blue, they should be rapidly washed in running -water and dryed in the shade. Silk stuffs are dyed in the same way; -<span class="pagenum" id="Page_059">59</span> -but the alum should be previously applied cold by means of a saturated -solution of alum, in which the stuffs should be immersed for an hour. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_6"></a><a href="#FNanchor_6"> -<span class="label">[6]</span></a> -<p class="c009"> -First sung by Mrs. Jordan, about the year 1799. -</p> -</div> - -<h3>COLORS NOT FAST.</h3> - -<p class="c009"> -In regard to all the combinations of indigo with sulphuric acid, -including the carmines, it must be observed that their application -does not constitute true indigo dyeing: the colors are not fast. It is -not pure indigotine which is fastened on the tissues as in the vat -dyeing, but another compound of indigo with the sulphur. Berzelius -observes that “the color of soluble indigo is fully as alterable and -fugacious as that of the colors extracted by the decoction of -vegetable materials. By a long exposure to the sun the indigo blue is -destroyed: it becomes green during evaporation, and changes its -nature.” The carmines as well as the sulphur acids are easily -decolorized by reducing agents, such as hydrogen and sulphuretted -hydrogen, although they gradually assume their original color when -exposed to the atmosphere. We are informed by some of the older -dealers that imported cloths and merino stuffs known as “Saxony” were -formerly largely sold in our shops, but that, notwithstanding their -attractiveness to purchasers, they were objectionable on account of -the instability of their color. -</p> - -<h3>APPLICATION OF INDIGO IN PRINTING STUFFS.</h3> - -<p class="c009"> -Our notes would be incomplete without some reference to the uses of -indigo in printing fabrics. In pursuing this branch, we are -embarrassed on the one hand by the consideration that the subject is -too technical for the general reader, and on the other by the -consciousness that it would be presumption in us to attempt to -instruct those skilled in the art. It may not, however, be without -benefit in producing a higher appreciation of science for the general -reader to observe how science comes in play, even in the printing of a -single color; while to the skilled reader our notes may possibly be of -value as a vehicle for conveying some receipts taken from works not -easily accessible. -</p> - -<p><span class="pagenum" id="Page_060">60</span> -</p> - -<h3>PRINTING STUFFS OF WOOL AND SILK, AND STUFFS WITH COTTON WARPS.</h3> - -<p class="c009"> -This branch of our subject is directly allied to the one last -considered, the application of the compounds of sulphur and indigo; -for indigo is applied to printing wool and silk principally in the -form of indigo carmines. These applications are less numerous than -they were formerly, since they have been replaced by Prussian blue, -and more recently by the aniline blues, which are now generally used. -When the carmines are used, it is for making sky blues, and they enter -into the composition of some greens and browns. The salts of alumina -and vegetable acids are used to fix the indigo carmine upon tissues of -wool and silk. Some receipts recommended by M. de Kæppelin, himself a -practical printer, are given in a note.<a - id="FNanchor_7"></a> <a href="#Footnote_7" - class="fnanchor">[7]</a> -</p> - -<p><span class="pagenum" id="Page_061">61</span> -</p> - -<p class="c009"> -In printing tissues of wool with cotton warp, the carmines are not -used alone. They are combined in certain proportions with cyanites of -iron and potash, to obtain upon the cotton a blue color of equal -intensity with that produced by the carmines upon wool. It is also -necessary to previously mordant the fabrics by means of a solution of -oxide of tin or caustic soda which is precipitated on the fibres by -passing through a bath of water, to which sulphuric acid has been added. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_7"></a><a href="#FNanchor_7"> -<span class="label">[7]</span></a> -<table class="table5" summary="Persoz mixture ratios"> - <tbody> - <tr> - <td class="c008 xsmall" colspan="5">BLUE NO. 1.</td> - </tr> - <tr> - <td class="c006 small">Indigo carmine</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - <td class="c007 small">400</td> - <td class="c006 small">grammes.</td> - </tr> - <tr> - <td class="c006 small">Alum</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - <td class="c007 small">100</td> - <td class="c008 small">„</td> - </tr> - <tr> - <td class="c006 small">Oxalic acid</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - <td class="c007 small">150</td> - <td class="c008 small">„</td> - </tr> - <tr> - <td class="c006 small">Boiling water</td> - <td class="c007 small">1¼</td> - <td class="c006 small">litre</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c020 small">Gum water prepared in proportion of 1 kilogram to the litre</td> - <td class="c007 small">1¼</td> - <td class="c006 small">litre</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c008 xsmall" colspan="5">GREEN NO. 1.</td> - </tr> - <tr> - <td class="c006 small">Gum water as above</td> - <td class="c007 small">12</td> - <td class="c006 small">litres.</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Cuba lac</td> - <td class="c007 small">12</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Alum</td> - <td class="c007 small">1</td> - <td class="c006 small">kilogram,</td> - <td class="c007 small">500</td> - <td class="c006 small">grammes.</td> - </tr> - <tr> - <td class="c006 small">Oxalic acid</td> - <td class="c007 small">2</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Indigo carmine</td> - <td class="c007 small">4</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c008 xsmall" colspan="5">BOUILLON FOR THE GREENS AND BLUES.</td> - </tr> - <tr> - <td class="c006 small">Boiling water</td> - <td class="c007 small">12</td> - <td class="c006 small">litres.</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Alum</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - <td class="c007 small">600</td> - <td class="c006 small">grammes</td> - </tr> - <tr> - <td class="c006 small">Oxalic acid</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - <td class="c007 small">750</td> - <td class="c008 small">„</td> - </tr> - <tr> - <td class="c006 small">Gum water</td> - <td class="c007 small">12</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c008 xsmall" colspan="5">SKY BLUE FOR WOOLLEN STUFF WITH COTTON WARP.</td> - </tr> - <tr> - <td class="c006 small">First solution.—Boiling water</td> - <td class="c007 small">4</td> - <td class="c006 small">litres.</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c007 small">Cyanuret of iron and potash</td> - <td class="c007 small"></td> - <td class="c008 small"></td> - <td class="c007 small">800</td> - <td class="c006 small">grammes.</td> - </tr> - <tr> - <td class="c006 small">Second solution.—Boiling water</td> - <td class="c007 small">2</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c007 small">Tartaric acid</td> - <td class="c007 small"></td> - <td class="c008 small"></td> - <td class="c007 small">300</td> - <td class="c008 small">„</td> - </tr> - <tr> - <td class="c006 small">Third solution.—Cold water </td> - <td class="c007 small">3</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c007 small">Sulphuric acid</td> - <td class="c007 small"></td> - <td class="c008 small"></td> - <td class="c007 small">300</td> - <td class="c008 small">„</td> - </tr> - <tr> - <td class="small" colspan="5">Pour in the first solution, then the second and third, agitating the -color with a spatula after each new addition.</td> - </tr> - <tr> - <td class="small" colspan="5">The following mixture is afterwards applied to the stuff:—</td> - </tr> - <tr> - <td class="c006 small">Gum water</td> - <td class="c007 small">12</td> - <td class="c006 small">litres.</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Water</td> - <td class="c007 small">6</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - <tr> - <td class="c006 small">Blue No. 1 for wool</td> - <td class="c007 small">3</td> - <td class="c008 small">„</td> - <td class="c007 small"></td> - <td class="c006 small"></td> - </tr> - </tbody> -</table> - -</div> - -<h3>APPLICATIONS OF INDIGO IN PRINTING COTTON FABRICS.</h3> - -<p class="c009"> -Before entering upon methods used in large establishments, it may not -be without interest to observe the processes still used in Java for -printing calicoes, which the natives prefer to any imported from -Europe. In Java there are no factories, and the women in each family -make and dye or print all the cotton cloths required for their own -consumption. They apply by means of a brush or pencil, which they use -with great skill, to the cotton tissue which they wish to cover a thin -coating of wax mixed with a little resin, the wax being applied to all -the parts where the design, which has been first traced upon the -cloth, requires that the fabric should remain uncolored. They then -immerse the stuff several times in an indigo vat until they have -obtained the desired tint. The stuff is afterwards washed and dried -for a new application of the wax, carefully applied with a pencil as -before. The cloth is then immersed in a bath of a different color, -made with madder or catechu, but always of some dye which is perfectly -stable; and the operation is repeated according to the number of -colors desired. By these successive applications of wax and immersions -into different vats, they succeed in producing very complicated and -harmonious colors, while no European goods compare with them in -stability of dye. -</p> - -<p class="c009"> -In the European, and our own manufacture, the blue bottoms upon -vegetable fibres, made by immersion in the indigo vat, are combined -with white impressions, or others variously colored, by two distinct -methods. Sometimes there is printed upon the cloth before dyeing in -the indigo vat a preparation called a reserve or resist, which -prevents the indigotine from being deposited in the places where it is -applied. Sometimes, on the <span class="pagenum" id="Page_062">62</span> contrary, the indigo, which has been -uniformly fixed upon the fabric, is destroyed in certain places marked -out by printing upon them certain chemical agents, called -<i>discharges</i>. -</p> - -<p class="c009"> -The <i>reserves</i> are mechanical, resisting the penetration of the dye, -such as wax and pipe clay, or chemical. The last, through these acid -or oxidizing properties, cause the precipitation of the indigotine -before it has touched the fibre or penetrated into its pores. Such are -the salts of copper and bi-chlorate of mercury. Other bodies perform -the part both of mechanical and chemical reserves. The salts of zinc -or alumina, for instance, which are frequently used, produce at the -same time a deposit of indigo white and a gelatinous covering of -hydrated oxide of zinc or aluminium. The composition of a good reserve -is declared to be principally a question of good proportions of the -constituent parts, varying with the strength of the vat and the -intensity of the blue which is desired to be reserved. The first -condition is that it hardens immediately after immersion in the vat: -if it softens, on the contrary, it will cause the running of the -color. In other words, the acidity of the impression should be -proportionate to the strength and alkaline character of the vat. The -white reserve, that most generally used, is composed of pipe clay, -gum, verdigris, and sulphate of copper. The styles of work produced by -dipping with reserves are generally of a cheap and low class. The -system is clumsy and expensive, and is only tolerated because of the -want of a method of directly applying indigo, which will yield the -deepest shades. -</p> - -<p class="c009"> -Certain styles, formerly in great vogue, called <i>Lapis</i>, and forming -one of the richest branches of the cotton-printing industry, are -founded upon the use of reserves; and in these styles, by very simple -means which we shall not attempt to describe, different colors -produced from madder, catechu, &c., are produced upon the fabric so -perfectly surrounded by blue that the eye cannot detect the slightest -want of continuity. This fabrication has the greatest perfection in -Russia. The imitation cashmere fabrics of cotton imported from that -country, formerly much in fashion for dressing-gowns, are specimens of -this fabrication. The great stability of the colors is a remarkable -feature of these -goods. -</p> - -<p><span class="pagenum" id="Page_063">63</span> -</p> - -<p class="c009"> -The system of resists or reserves possesses the inconveniences of not -producing impressions of great firmness, and of requiring very strong -vats. When the strength of the vat is partially exhausted, they may be -thrown aside. These inconveniences are obviated by the system of -discharges (<i>enlevages</i>). In this system the cloths are vat dyed of a -uniform blue. The strength of the vat is of less importance, and it -can be used until the indigo is quite exhausted. The means of -destroying the indigo which has been fixed upon the fibre are founded -on the use of active oxidizing agents, which transform the insoluble -indigotine into soluble isatine. The agent generally used is chromic -acid. As this acid cannot be incorporated with the thickening to be -printed, as the thickening would produce oxide of chrome, the cloth is -passed through a strong solution of chromate of potash, and dried in -the shade. The required pattern is then printed on the cloth with a -mixture whose principal elements are acids which are susceptible of -setting free the chromic acid on the tissue, which then acts upon the -indigo producing a white pattern. The acid generally employed for -freeing the chromic acid is oxalic acid, thickened with British gum, -dextrine, or starch, with the addition of pipe clay. To prevent -running, nitric, sulphuric, or tartaric acid are sometimes used.<a - id="FNanchor_8"></a> <a href="#Footnote_8" - class="fnanchor">[8]</a> -</p> - -<p><span class="pagenum" id="Page_064">64</span> -</p> - -<p class="c009"> -By the method of discharges the white designs upon blue are brought -out with a distinctness which it is impossible to obtain by resists, -while the most delicate work of the graver can be exactly reproduced -upon the tissue. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_8"></a><a href="#FNanchor_8"> -<span class="label">[8]</span></a> -<p class="c009"> -Schutzenberger gives the following receipts:— -</p> - -<table class="table5" summary="Schutzenberger receipts"> - <tbody> - <tr> - <td class="c008 xsmall" colspan="2">PREPARATION FOR DISCHARGE.</td> - </tr> - <tr> - <td class="c006 small">Water</td> - <td class="c024 small">2 litres.</td> - </tr> - <tr> - <td class="c006 small">Yellow chromate</td> - <td class="c024 small">500 grammes.</td> - </tr> - <tr> - <td class="c008 xsmall" colspan="2"> </td> - </tr> - <tr> - <td class="c008 xsmall" colspan="2">WHITE DISCHARGE ON BLUE BOTTOM.</td> - </tr> - <tr> - <td class="c006 small">Tartaric acid</td> - <td class="c024 small">3 kilograms.</td> - </tr> - <tr> - <td class="c006 small">Oxalic acid</td> - <td class="c024 small">250 grammes.</td> - </tr> - <tr> - <td class="c006 small">Burnt starch</td> - <td class="c024 small">4 kilograms.</td> - </tr> - <tr> - <td class="c006 small">Nitric acid</td> - <td class="c024 small">500 grammes.</td> - </tr> - <tr> - <td class="c006 small">Water</td> - <td class="c024 small">4 litres.</td> - </tr> - </tbody> -</table> - -<p class="c009"> -De Kæppelin gives the following:— -</p> - -<table class="table5" summary="De Kæppelin receipts"> - <tbody> - <tr> - <td class="c008 xsmall" colspan="2">WHITE DISCHARGE ON BLUE.</td> - </tr> - <tr> - <td class="c006 small">Water</td> - <td class="c024 small">2 litres.</td> - </tr> - <tr> - <td class="c006 small">Starch</td> - <td class="c024 small">1 kilogram, 800 grammes.</td> - </tr> - <tr> - <td class="c006 small">Oxalic acid</td> - <td class="c024 small">500 grammes.</td> - </tr> - <tr> - <td class="c006 small">Tartaric acid</td> - <td class="c024 small">250 grammes.</td> - </tr> - <tr> - <td class="c006 small">Sulphuric acid</td> - <td class="c024 small">375 grammes.</td> - </tr> - </tbody> -</table> - -<p class="c009"> -The pieces, having been dyed blue, are then placed in a solution of -bichromate of potash in water, which is prepared in the ratio of 50 to -60 grammes to the litre, according to the intensity of the blue. The -pieces thus prepared must be dried away from direct solar light or too -much heat. In fact, under the action of these agents, the bichromate -would be decomposed and the tissue altered. The pieces are often -rolled up to prevent this effect. After the pieces are printed, they -are passed into a vessel containing water and holding chalk in -suspension in sufficient quantity to give it a milky aspect. The -temperature of the bath is raised to 60° R. The excess of acid of the -color applied is saturated by the chalk, and the excess of bichromate -of potash with which the tissue is impregnated is dissolved in the -bath. The pieces are afterwards washed and passed through slightly -soapy water. -</p> - -</div> - -<h3>APPLICATION OF INDIGOTINE BY PRINTING.</h3> - -<p class="c009"> -The first step in the art of printing indigotine upon calicoes was the -application of what is called pencil blue. Instead of immersing the -fabrics in an indigo vat, the indigo white formed in a very strong -indigo vat was thickened and applied locally to certain places on the -cloth. The preparation was painted upon the cloth by means of pencils -made of willow sticks, the ends of which were broomed up into a kind -of brush. The style was hence called pencil blue. The methods now used -to apply white indigo locally are of two kinds. The china blue -process, and the solid blue process, sometimes called fast or -precipitated blue. The china blue process derives its name from the -resemblance of its color to the blue on the old china ware. It has -great depth of tint, and permanency. It is scarcely used now, except -for certain articles requiring great depth of color, such as certain -furniture goods, and by the Germans and Swiss for the manufacture of -calicoes for exportation to India. -</p> - -<p class="c009"> -We do not venture to condense the descriptions at our hand of the -processes for applying the china blue and the solid blue, and -translate those furnished by chemists of high authority. After the -method indicated by Darwin in his recent works, we present them in -smaller type, with the perhaps unnecessary suggestion that they may be -passed over by the general reader. -</p> - -<p class="c009"> -<i>China blue</i>.—The theory of this printing blue, says Schutzenberger, -is very simple. The indigo, reduced to an impalpable powder and -<span class="pagenum" id="Page_065">65</span> -thickened, is printed by a plate or roller. After drying, the tissue -seems dyed blue, more or less deep, according to the proportion of -coloring material used; but it is only a blue of application, which -can be removed with the thickening, by the slightest washing. The -object is now to reduce and redissolve the indigotine in place to -enable it to penetrate the fibre at the end of a consecutive -oxidization, and without producing a running of the color or altering -the purity and distinctness of the contours of the design. I owe to M. -Ed. Schwartz some valuable hints upon the fabrication of this style, -which is also described with much care and details in the treatise on -printing by M. Persoz. -</p> - -<p class="c009"> -The reduction of the indigo is obtained by alternate passages of the -printed tissue into vats containing,—the first, quicklime slacked; the -second, sulphate of iron; the third, soda. The operation is terminated -by a passage through a bath of sulphuric acid, which removes the oxide -of iron and precipitates the indigo white by hastening its oxidation. -</p> - -<p class="c009"> -The success depends upon the composition of the color printed, and -above all upon the strength of the vats of immersion and the duration -of the treatment. -</p> - -<p class="c009"> -The operator uses six vats,—for instance, two lime vats, provided each -with 12 kilograms of lime; a copperas vat at 70 Beaumé; a caustic soda -vat marking 140 Beaumé; a sulphuric acid vat with 500 grammes of acid -(<i>par mesure d’eau</i>); and finally a vat of pure water. -</p> - -<p class="c009"> -The receipts for printing are:— -</p> - -<table class="table5" summary="China blue 1"> - <tbody> - <tr> - <td class="c008 xsmall" colspan="3">1. THE BLUE PREPARATION.</td> - </tr> - <tr> - <td class="c006 small">Ground indigo</td> - <td class="c007 small">4</td> - <td class="c006 small">kilograms.</td> - </tr> - <tr> - <td class="c006 small">Acetate of iron</td> - <td class="c007 small">10</td> - <td class="c006 small">litres.</td> - </tr> - <tr> - <td class="c006 small">Sulphate of iron</td> - <td class="c007 small">1</td> - <td class="c006 small">kilogram.</td> - </tr> - <tr> - <td class="c006 small">Water </td> - <td class="c007 small">10</td> - <td class="c006 small">litres.</td> - </tr> - <tr> - <td class="c006 small">Gum Senegal</td> - <td class="c007 small">6</td> - <td class="c006 small">kilograms.</td> - </tr> - </tbody> -</table> - -<p> -Pass through a sieve; leave some time at rest, and stir whenever used. -Caraccas indigo is preferred because it can be broken into a finer -powder and gives a finer paste. -</p> - -<table class="table5" summary="China blue 2"> - <tbody> - <tr> - <td class="c008 xsmall" colspan="2">2. COLORS FOR ROLLER PRINTING NOS. 1, 2, 3, 4.</td> - </tr> - <tr> - <td class="c006 small">The blue preparation above</td> - <td class="c007 small">1, 1, 3, 4.</td> - </tr> - <tr> - <td class="c006 small">Acetate of iron containing 700 grammes of gum per litre</td> - <td class="c007 small">2, 1½, ½, ½.</td> - </tr> - <tr> - <td class="c006 small">Gum water at 600 grammes per litre</td> - <td class="c007 small">16, 2½, ½, ½.</td> - </tr> - </tbody> -</table> - -<p class="small">These proportions can be varied according to the tint desired. -</p> - -<p><span class="pagenum" id="Page_066">66</span> -</p> - -<p class="c009"> -The piece is treated a quarter of an hour in the first lime vat by -giving it a light movement from above to below; it is left a quarter -of an hour in repose in the sulphate of lime vat; a quarter of an hour -in the second lime vat; a quarter of an hour in the copperas vat; five -minutes in the caustic soda; half an hour in the sulphuric acid, and -then thoroughly rinsed. -</p> - -<p class="c009"> -To each lime vat there is given 2 kilograms of lime per piece of -cloth. To the vitriol vat there is added 50 kilograms of sulphate of -iron for each dozen pieces. The soda vat is renewed after 5 pieces by -the addition of 12 kilograms of salt of soda, which has first been -made caustic. The acid vat receives 25 kilograms of acid after 5 -pieces, and ought to be renewed whenever it becomes saline. The other -vats must be cleared out whenever the deposit becomes too great for -success. -</p> - -<p class="c009"> -M. Ed. Schwartz recommends as important conditions, (1) the perfect -causticity of the tissue, and an average strength of 140 Beaumé; (2) -the neutrality of the sulphate of lime vat. For this end old iron -should be boiled in it. -</p> - -<p class="c009"> -After leaving the sulphuric acid vat the pieces are rinsed in the -water vat, then in river water, and afterwards should be soaked in a -sulphuric acid bath at 40 Beaumé, for the purpose of dissolving the -last traces of the peroxide of iron adhering to the fibre. The fabric -is then washed in water and finally passed through a soapy water at -40° R. -</p> - -<p class="c009"> -<i>Solid or precipitated blue, Schutzenberger’s receipt</i>.—The process -consists in printing indigo white precipitated in a vat, in a thick -paste to dissolve it on the tissue by a passage through an alkaline -bath (lime or soda), and of reprecipitating it by oxidizing it as soon -as it has entered the fibre. -</p> - -<p class="c009"> -It is then the china blue process, minus the reduction which is made -before printing, and consequently minus the sulphate of iron vat. -</p> - -<p class="c009"> -Indigo white is too alterable to be printed with success, so it is -generally precipitated in combination with a stannic hydrate (hydrate -of a salt of tin), which gives it body and preserves it from a too -rapid oxidation. -</p> - -<p class="c009"> -The stannic indigotate in paste, or as it is generally called -precipitate of indigo, is prepared by turning into the clear portion -of a strong copperas vat an acid solution of protochlorate of tin, and -filtering it upon woollen filters,—as much as possible away from the -air. <span class="pagenum" id="Page_067">67</span> It would be better to prepare a strong tin vat by heating a -mixture of indigo, caustic soda, and protochlorate of tin, and to -precipitate by chlorohydric acid.<a - id="FNanchor_9"></a> <a href="#Footnote_9" - class="fnanchor">[9]</a> -</p> - -<p class="c009"> -The deposit is made into a paste with gum water; a salt of tin is -often added to prevent oxidation. It is important to prevent the -transformation of the indigo white into indigotine before printing. -This indigotine would not fix itself on the fabric. Moreover, after -printing, it is necessary to hasten the dissolution of the indigo -white to enable it to penetrate the fibre. It is sufficient for this -end to pass it through milk of lime. The stannic combination is -immediately destroyed; the colorable matter unites itself with the -lime, and the color passes into a pale gray with apple green. The -indigo white becomes momentarily soluble; but the presence of the -excess of lime and the thickening, as well as the attractive affinity -of the thickening, prevent any running. -</p> - -<p class="c009"> -The piece on issuing from the lime water is placed in running water, -when reoxidation commences, which this time fixes the color. The piece -is finally passed through a sulphuric acid bath to absorb the lime, -and washed. -</p> - -<p class="c009"> -By adding to the color a salt whose base precipitates in the milk of -lime and oxidizes in the running water, and replacing the simple acid -bath by an acid bath with yellow prussite, the intensity of the blue -is increased through the formation of Prussian blue. -</p> - -<p><span class="pagenum" id="Page_068">68</span> -</p> - -<p class="c009"> -Although we have seen beautiful effects from the application of the -solid blue of indigo on prints at our Pacific Mills, the colors -produced by Prussian blue and aniline are so much more brilliant and -easy of application that the use of indigo in printing goods for -ordinary consumption is likely to decline rather than increase. It -will be otherwise if we should ever manufacture for the East India -markets. Here is a field still open for our manufacturers. Mr. Watson, -in his beautiful work on “The Costumes of the People of India,” -remarks that “British manufacturers have hitherto failed to appreciate -Oriental tastes and habits, and hence supply but an insignificant part -of the clothing of the two hundred million persons that form the -population of what is commonly spoken of as India.” The great defect, -he observes, is the want of stability of color in the cotton fabrics -introduced,—this stability being an imperative demand in the Oriental -markets. -</p> - -<p class="c009"> -The applications of indigo to cotton fabric are altogether secondary, -in our mind, to its relations to the woollen manufacture. If we have -felt called upon to say a word in behalf of the most ancient and best -ally which the fibre of wool has ever had, it is because the vividness -of color of the new products of coal, and the fascination which the -application of the recent discoveries of science always possesses, is -threatening the eclipse of the more ancient sober and solid dyes. Let -the new colors have their place as auxiliaries, not as substitutes for -the ancient dyes. Let them serve to give a bloom<a - id="FNanchor_10"></a> <a href="#Footnote_10" - class="fnanchor">[10]</a> to goods, but let -the foundation be the good old dyes which the experience of ages has -proved to be the most unalterable by light and air. The recent -wonderful discovery of alizarine, or artificial madder, in coal tar -products, has led practical men to expect too much from science. The -opinion is quite prevalent among manufacturers that artificial -indigotine has already been obtained from the <span class="pagenum" id="Page_069">69</span> same source. And some -manufacturers are sanguine that the difficulties of indigo dyeing will -thus be resolved. It is not improbable—for what is impossible to -modern chemistry?—that this result will yet be partially obtained. But -we have looked over all the recent foreign chemical reviews, and -personally consulted some of our best chemists, and we can find no -authority for the prevailing opinion that artificial indigotine has -been produced. If the production of artificial indigotine should be -realized, the only benefit would be the possible cheapening of the -material. The difficulties of the indigo vat would still remain; for -we cannot too often repeat, that in the very difficulties of the -process, or in the insolubility of blue indigotine by ordinary agents, -consists the excellence of the dye. -</p> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_9"></a><a href="#FNanchor_9"> -<span class="label">[9]</span></a> -<p class="c009"> -Mr. T. P. Shepard gives in his valuable “Receipts for Calico -Printing,” published in 1872, the following:— -</p> - -<p class="c008">NO. 52. INDIGO PRECIPITATE FOR FAST BLUE AND GREEN. -</p> - -<ul> -<li><span class="small">10 pounds quicklime, slacked with</span></li> -<li><span class="small">6½ gallons water; then</span></li> -<li><span class="small">2 pounds ground indigo finely rubbed in water are stirred in; then add</span></li> -<li><span class="small">6 pounds copperas dissolved in 5 gallons of water; then add</span></li> -<li><span class="small">5 gallons hot water and</span></li> -<li><span class="small">15 gallons cold water.</span></li> -<li><span class="small">Stir well from time to time, until the liquid has assumed a yellow -color and deep blue veins or streaks appear on its surface. When this -moment arrives, draw off the clear liquor, and precipitate every ten -quarts of it with</span></li> -<li><span class="small">½ pound tin crystals, dissolved in ½ pound muriatic acid.</span></li> -<li><span class="small">To the remainder of the mixture of lime and indigo, 15 gallons of -water may be added, and the whole stirred; and when settled, the -indigo may be precipitated from the clear liquor as before. This -operation may be repeated a second time before all the indigo is -exhausted.</span></li> -</ul> - -<p class="c009"> -The indigo precipitate is to be collected on a muslin filter, and -well squeezed out. -</p> -</div> - -<div class="footnote"> -<a id="Footnote_10"></a><a href="#FNanchor_10"> -<span class="label">[10]</span></a> -<p class="small c009"> -<i>Guernsey Blue</i>.—The darkest of the Nicholson Fast Blues. On a -bottom of barkwood, camwood, madder, or inferior <i>indigo</i>, produces -an indigo blue which will stand all the acid tests the same as -colors made from indigo. -</p> - -<p class="small c009"> -<i>Serge Blue</i>.—It will be found very serviceable to give bloom to -goods dyed with indigo, and by itself shows a very good indigo test -with nitric acid.—<i>Instructions for Working the Atlas Works Aniline -Dyes</i>. -</p> -</div> - -<div class="section"> -<h2 class="nobreak">APPENDIX.</h2> -</div> - -<h3>DYEING WOOL IN THE WARM INDIGO VAT.</h3> - -<p class="c008">[<i>Extract from Dumas’s Lectures on Dyeing</i>.] -</p> - -<p class="c009"> -The value attached by practical wool-dyers to the following induces us -to publish it without condensation:— -</p> - -<div class="c039"> - -<p class="c009 c040"> -<span class="smcap">Indigo Blue.</span>—We give a solid dye of indigo blue to wool by plunging it -into an alkaline solution of indigo white, and then exposing it to -contact with the air. The solution of indigo white is prepared in a -vessel usually from eight to nine feet in depth, and six to seven feet -in diameter. This size is very convenient for the requisite -manipulations, and presents a large volume of water, which, when once -heated, is capable of preserving a high temperature for a long time. -This vessel should be made of wood or copper. It always bears the name -of vat. These vats are covered with a wooden lid, divided into two or -three equal segments. Over this lid are spread some thick blankets. -Without this precaution the bath would come in contact with the -atmospheric air, a portion of the indigo would absorb oxygen and -become precipitated. There would also be a great waste of heat. -</p> - -<p class="c009"> -A most necessary operation, and one which has to be frequently -repeated, consists in stirring up the deposit of vegetable and -coloring matter which is formed in the vat, and intimately mixing it -in the bath. For this purpose we employ a utensil called a <i>rake</i>, -which is formed of a strong square piece of wood, set on a long -handle. The workman takes hold of this with both hands, and, dipping -the flat surface into the deposit at the bottom of the vessel, he -quickly <span class="pagenum" id="Page_070">70</span> draws it up until it nearly reaches the surface, when, giving -it a gentle shake, he discharges the matter again through the liquor -of the bath. This manœuvre is repeated until the whole of the deposit -seems to be removed from the bottom of the vessel. Before the tissue -is dipped into the dye-bath, it should be soaked in a copper full of -tepid water; it is then to be hung up and beaten with sticks. In this -state it is plunged into the vat; it thus introduces less air into the -bath, while it is more uniformly penetrated by the indigo solution. -The cloth is now kept at a depth of from two to three feet below the -surface of the liquid, by means of an open bag or piece of network -fixed in the interior of an iron ring, which is suspended by cords, -and fixed to the outside of the vat by means of two small iron hooks; -the bag is thus drawn backwards and forwards without permitting it to -come in contact with the air. When this operation has been continued -for a sufficient length of time, the cloth is wrung and hung up to dry. -</p> - -<p class="c009"> -Flock wool is also, for the purpose of dyeing, enclosed in a fine net, -which prevents the least particle from escaping, and which is fixed in -the bath in the same way as in the foregoing case. -</p> - -<p class="c009"> -The many inconveniences attending the use of wooden baths, which -necessitate the pouring of the liquor into a copper for the purpose of -giving it the necessary degree of heat, have led to the general -employment of copper vessels. These are fixed in brickwork, which -extends half way up their surface, whilst a stove is so constructed at -this elevation that the flame shall play around their upper part. By -this means the bath is heated and kept at a favorable temperature -without the liquor being obliged to be removed. -</p> - -<p class="c009"> -The potash vats are usually formed of conical-shaped coppers, -surrounded by a suitable furnace. These may be constructed with less -depth, inasmuch as there is less precipitation induced in the liquor. -By using steam for heating the vats, we might dispense with the -employment of copper vessels, and so return to those of wood. -</p> - -<p class="c009"> -The vats employed for dyeing wool are known under the names of the -pastel vat, the woad vat, the potash vat the tartar-lee vat, and the -German vat. -</p> - -<p class="c009"> -<span class="smcap">Pastel Vat.</span><a - id="FNanchor_11"></a> <a href="#Footnote_11" - class="fnanchor">[11]</a>—The first care of the dyer in preparing the vat should -be to furnish the bath with matters capable of combining with the -oxygen, whether directly or indirectly, and of giving hydrogen to the -indigo. We must, however, be careful to employ those substances only -which are incapable of imparting to the bath a color which might prove -injurious to the indigo. These advantages are found in the pastel, the -woad, and madder. This latter substance furnishes a violet tint when -brought into contact with an alkali, and by the addition of indigo it -yields a still deeper shade. -</p> - -<p class="c009"> -In preparing the Indian vat, we ordinarily employ one pound of fine -madder to two pounds of indigo. The madder is here especially useful, -by reason of the avidity of some of its principles for oxygen. -</p> - -<p class="c009"> -The pastel vat, when prepared on a large scale, ordinarily contains -from 18 to 22 lbs. of indigo; 11 lbs. of madder would suffice for this -proportion, but we must also bear in mind the large quantity of water -which we have to charge with oxidizable matters. I have invariably -seen the best results from employing -<span class="pagenum" id="Page_071">71</span> 22 lbs. to a vat of this size. -Bran is apt to excite the lactic fermentation in the bath, and should -therefore not be employed in too large a quantity; 7 to 9 lbs. will be -found amply sufficient. -</p> - -<p class="c009"> -Weld, which is often used, is rich in oxidizable principles; it turns -sour, and passes into the putrid fermentation with facility. Some -dyers use it very freely; but ordinarily we employ in this bath an -equal quantity of it to that of the bran. Sometimes weld is not added -at all. -</p> - -<p class="c009"> -In most dye-houses the pastel is pounded before introducing it into -the vat. Some practical men, however, maintain that this operation is -injurious, and that it interferes with its durability. This is an -opinion which deserves attention. The effect of the pastel, when -reduced to a coarse powder, is more uniform; but this state of -division must render its alterations more rapid. When the bath has -undergone the necessary ebullition, the pastel should be introduced -into the vat, the liquor decanted, and at the same time 7 or 8 lbs. of -lime added, so as to form an alkaline lye which shall hold the indigo -in solution. Having well stirred the vat, it should be set aside for -four hours, so that the little pellets shall have time to become -thoroughly soaked, both inside and out, and thus be prepared for -fermentation. Some think coverings are to be spread over the vat, so -as to preserve it from contact with the atmosphere. After this lapse -of time, it is to be again stirred. The bath at this moment presents -no decided character; it has the peculiar odor of the vegetables which -it holds in digestion; its color is of a yellowish-brown. -</p> - -<p class="c009"> -Ordinarily, at the end of twenty-four hours, sometimes even after -fifteen or sixteen, the fermentative process is well marked. The odor -becomes ammoniacal, at the same time that it retains the peculiar -smell of the pastel. The bath, hitherto of a brown color, now assumes -a decided yellowish-red tint. A blue froth, which results from the -newly liberated indigo of the pastel, floats on the liquor as a thick -scum, being composed of small blue bubbles, which are closely -agglomerated together. A brilliant pellicle covers the bath, and -beneath we may perceive some blue or almost black veins, owing to the -indigo of the pastel which rises towards the surface. If the liquor be -now agitated with a switch, the small quantity of indigo which is -evolved floats to the top of the bath. On exposing a few drops of this -mixture to the air, the golden-yellow color quickly disappears, and is -replaced by the blue tint of the indigo. This phenomenon is due to the -absorption of the oxygen of the air by the indigogen from the pastel: -in this state we might even dye wool with it without any further -addition of indigo; but the colors which it furnishes are devoid of -brilliancy and vivacity of tone, at the same time that the bath -becomes quickly exhausted. -</p> - -<p class="c009"> -The signs above described announce, in a most indubitable manner, that -fermentation is established, and that the vat has now the power of -furnishing to the indigo the hydrogen which is required to render it -soluble,—that contained in the pastel having been already taken up; -this, then, is the proper moment for adding the indigo, which should -be previously ground in a mill. -</p> - -<p class="c009"> -We stated above that the liquor of the vat should be previously -charged with a certain quantity of lime; we also find in it ammonia -generated by the pastel; but a part of these alkalies become saturated -by the carbonic acid gas along with the proper acids of the madder and -of the weld, as well as by the lactic acid produced by the bran during -fermentation. The ordinary guide of the dyer is the odor, which, -according to circumstances; becomes more or less ammoniacal. The vat -is said to be either soft or harsh; if soft, a little more lime should -be added to it. The fresh vat is always soft; it exhales a feeble -<span class="pagenum" id="Page_072">72</span> -ammoniacal odor accompanied with the peculiar smell of the pastel; we -must, therefore, add lime to it along with the indigo; we usually -employ from five to six pounds, and, after having stirred the vat, it -is to be covered over. The indigo, being incapable of solution except -by its combination with hydrogen, gives no sign of being dissolved -until it has remained a certain time in the bath. We may remark that -the hard indigoes, as those of Java, require at least eight or nine -hours, whilst those of Bengal do not need more than six hours, for -their solution. We should examine the vat again three hours after -adding the indigo. We ordinarily remark that the odor is by this time -weakened; we must now add a further quantity of lime, sometimes less, -but generally about equal in amount to the first portion; it is then -to be covered over again, and set aside for three hours. -</p> - -<p class="c009"> -After this lapse of time, the bath will be found covered with an -abundant froth and a very marked copper-colored pellicle; the veins -which float upon its surface are larger and more marked than they were -previously; the liquor becomes of a deep yellowish-red color. On -dipping the rake into the bath, and allowing the liquid to run off at -the edge, its color, if viewed against the light, is of a strongly -marked emerald-green, which gradually disappears, in proportion as the -indigo absorbs oxygen, and leaves in its place a mere drop rendered -opaque by the blue color of the indigo. The odor of the vat at this -instant is strongly ammoniacal; we also find in it the peculiar scent -of the pastel. When we discover a marked character of this kind in the -newly formed vat, we may without fear plunge in the stuff intended to -be dyed; but the tints given during the first working of the vat are -never so brilliant as those subsequently formed; this is owing to the -yellow-coloring matters of the pastel, which, aided by the heat, -become fixed on the wool at the same time as the indigo, and thus give -to it a greenish tint. This accident is common both with the pastel -and the woad vats; it is, however, less marked in the latter. -</p> - -<p class="c009"> -When the stuff or cloth has been immersed for an hour in the vat it -should be withdrawn; it would, in fact, be useless to leave it there -for a longer time, inasmuch as it could absorb no more of the coloring -principle. It is therefore to be taken from the bath and hung up to -dry, when the indigo, by attracting oxygen, will become insoluble and -acquire a blue color. Then we may replunge the stuff in the vat, and -the shade will immediately assume a deeper tint, owing to renewed -absorption of indigo by the wool. By repeating these operations, we -succeed in giving very deep shades. We must not, however, imagine that -the cloth seizes only on that portion of indigo contained in the -liquor required to soak it. Far from such being the case, experience -shows that, during its stay in the bath, it appropriates to itself, -within certain limits, a gradually increasing quantity of indigo. We -have here, then, an action of affinity, or perhaps a consequence of -porosity on the part of the wool itself. -</p> - -<p class="c009"> -<span class="smcap">Woad Vat.</span>—These vats are extensively employed at Louviers, and in the -manufactories of the north of France. The bath is prepared in the same -manner as in the foregoing case; the finely cut root is introduced -into the copper along with 2 lbs. of pounded indigo, 9 lbs. of madder, -and 15½ lbs. of slaked lime. The liquor is, after the necessary -ebullition, poured upon the woad. This substance contains but a very -small quantity of coloring principle; we must, therefore, add some -indigo when preparing the vat, so as to indicate the precise instant -when the mixture arrives at the point of fermentation so necessary for -imparting hydrogen to the coloring principle, and for rendering it -soluble. We must also use a larger quantity of lime, since the woad -contains no ammonia <span class="pagenum" id="Page_073">73</span> resulting from previous decomposition, such as we -find to be the case with the pastel of the south. When the vat is in a -suitable state of fermentation, a rusty color becomes manifest, in -addition to the signs already described in speaking of the pastel vat; -besides the ammoniacal odor, the bath always retains the peculiar -smell of the woad. The pounded indigo is now added, and we proceed, in -the manner already detailed, to reduce it to a state of solution fit -for dyeing. -</p> - -<p class="c009"> -The vats prepared by means of pastel have greater durability than -those made with the woad; but it is thought that the colors given by -the latter are more brilliant than those obtained from the former dye. -</p> - -<p class="c009"> -<span class="smcap">Modified Pastel Vat.</span>—This vat is about 7 feet in depth, and 6½ feet -in diameter. It is made of copper, and heated by steam. The lid is -composed of three segments, each of which is formed of two planks, -about an inch thick, and strongly secured together by bolts. -</p> - -<p class="c009"> -The beating is performed in the usual way, with sticks before the -first dipping, after having moistened the cloth in tepid water. This -operation is not subsequently repeated. -</p> - -<p class="c009"> -This vat is prepared with 13 lbs. of indigo, 17½ lbs. of madder, 4½ -lbs. of bran, 9 lbs. of lime, and 4½ lbs. of potash. Having filled the -vat, we heat it to about 200° Fah., and, as soon as the water is -tepid, introduce 441 lbs. of pastel. The liquor becomes of a -yellowish-brown color; small bubbles appear upon its surface, -ordinarily at the end of four hours if the vat be heated by steam, but -not until after eight or twelve hours where heat is applied by the -common fire; in the latter case the mixture should be stirred every -three hours. When the liquor displays the signs of fermentation, we -add the above-mentioned ingredients, and cover the vat over; it is -then to be set aside, stirring it every three hours, or oftener if the -fermentative action be very rapid. Each time that it is stirred we are -to add from 2 to 4 lbs. of lime; if fermentation proceed quickly we -even use more, but in the contrary case less. After about eighteen -hours, we plunge into the vat three pieces of common cloth, measuring -from twenty to twenty-five ells in length each; when they have -received six or seven turns, they are to be taken out again. The -object of this is to remove the excess of lime from the bath. The vat -is then set aside for three hours, when it is to be stirred, and 13 -lbs. of indigo, with 2 lbs. of madder, added to it. We now again apply -heat to the mixture. -</p> - -<p class="c009"> -If the vat contains a superabundance of lime, it will be unnecessary -to add more; otherwise we throw in a further quantity. During the -night it should be covered with a cloth, and a workman left to watch -it. It is usually stirred once before the morning; but if it be -deficient in lime, it will require this manipulation to be more -frequently repeated, and also fresh lime added to it. On the following -day the stirring should be continued every three hours, and so on for -the next thirty hours, taking care to heat the vat from time to time. -On the morning of the fourth day the dyeing may be commenced. -</p> - -<p class="c009"> -The temperature should be maintained at a pretty uniform point; if it -be too hot, the blue takes a red reflection, by reason of the madder -contained in the liquid. A vat thus prepared will last three months; -we may even work it for double that period, but after the third month -it appears to lose some of its indigo. -</p> - -<p class="c009"> -We maintain the power of the vat by introducing every night 2¼ lbs. of -madder. Some indigo is also added twice or three times a week. These -additions are made in the evening. After the former, the vat is left -at rest for forty-two hours; with the latter only for twenty-four, at -the same time observing <span class="pagenum" id="Page_074">74</span> the precautions already indicated. At the end -of three months, or sooner when we wish to stop the working of the -vat, we exhaust the indigo; for this purpose we continue to charge it -every night for the space of a month with madder, and dip into it -white cloths, or more particularly woollen tissues, which become more -or less loaded with the indigo. We must continue this plan until these -matters take up no further color. The dippings are to be performed -twice a day at first, but once only towards the termination. Many -dyers make use of this bath for preparing a new vat, but it is better -to throw this away and make it up afresh with common water. -</p> - -<p class="c009"> -<span class="smcap">Indian Vat.</span>—These vats are of more simple and of more ready -construction than the pastel or woad vats. We are to boil in water a -quantity of madder and of bran, proportioned to the weight of indigo -which we wish to employ. After two hours’ ebullition, we turn into -this bath some tartar-lees, which are also to be boiled for an hour -and a half or two hours, so as to charge the bath with whatever -soluble matter they may contain; after this ebullition the bath should -be allowed to cool, and the indigo, which has been previously ground, -is then to be introduced. Supposing that we wish to employ 21 lbs. of -indigo, the following would be the proportions used in preparing this -vat: 41 lbs. tartar-lees, 13 lbs. of madder, and 5 lbs. of bran. These -vats are usually mounted in coppers of a conical shape; a small fire -should be kept up around them, so as to maintain a moderate and -uniform heat. The indigo will usually be found dissolved at the end of -twenty-four hours, often even after twelve or fifteen hours. The -liquor has a reddish color in the new vats, and a green tint in those -which are in a working state. The frothy surface, as well as the -brilliant-colored pellicle, becomes manifested in this as in all other -preparations of a like kind. -</p> - -<p class="c009"> -This species of vat has to be renewed much more frequently than the -woad and pastel vats, from the indigo being more difficult to dissolve -after a certain lapse of time. A moderate heat should be maintained in -all these vats. -</p> - -<p class="c009"> -<span class="smcap">Potash Vat.</span>—This species of vat is extensively employed at Elbœuf for -the dyeing of wool in the flock. It presents in all respects a perfect -analogy with the Indian vat; in fact, the action of the tartar-lee in -the latter preparation depends entirely on the carbonate of potash -which it contains. The ingredients used in the preparation of the -potash vat are bran, madder, and the subcarbonate of potash of commerce. -</p> - -<p class="c009"> -We obtain the deep shades in this species of vat with greater celerity -than in all others, a fact which undoubtedly depends on the greater -power which potash has of dissolving indigo than is possessed by lime. -Experience proves that the potash vat has the advantage in point of -celerity of nearly a third; but this is balanced by the inconvenience -resulting from the darker shade, which we must attribute to the large -quantity of coloring matter of the madder dissolved by the alkaline -lee, and which becomes fixed on the stuff with the indigo. -</p> - -<p class="c009"> -To render this vat in its most favorable state, the indigo should be -made to undergo a commencement of hydrogenation before turning it into -the mixture; for this purpose we prepare in a small copper a bath -analogous to that in the vat, to which the pounded indigo is added. -This bath is maintained for twenty-four hours at a moderate heat, -taking care to stir it from time to time. The indigo assumes a -yellowish color, becomes dissolved, and in this state is turned into -the vat; we thus avoid many delays and losses in its preparation, and -indeed it would be desirable if a similar plan were adopted with all -these compounds. -</p> - -<p class="c009"> -<span class="smcap">German Vat.</span>—This vat is of nearly similar dimensions to that used for -the woad, being three times the size of the potash vat. Its diameter -is about 6½ feet, <span class="pagenum" id="Page_075">75</span> and its depth 8½ feet. Having filled the copper with -water, we are to heat it to 200° Fah.; we then add 20 pailsful of -bran, 22 lbs. of carbonate of soda, 11 lbs. of indigo, and 54 pounds -of lime, thoroughly slaked, in powder. The mixture is to be well -stirred, and then set aside for two hours; the workman should -continually watch the progress of the fermentation, moderating it more -or less by means of lime or carbonate of soda, so as to render the vat -in a working state at the end of twelve, fifteen, or, at the most, -eighteen hours. The odor is the only criterion by which the workman is -enabled to judge of the good state of the vat, he must therefore -possess considerable tact and experience. -</p> - -<p class="c009"> -In the process of dipping we introduce 84 lbs., 106 lbs., or even 130 -lbs. of wool, in a net bag, similar to that used in the woad vat, -taking care that the bag is not allowed to rest against the sides of -the copper. When the wool has sufficiently imbibed the color, we -remove the bag containing it, and allow it to drain for a short time -over the vessel. We operate in this way on two or three quantities in -succession; we then remove the vat, and set it aside for two hours; we -must be careful, from time to time, to replace the indigo absorbed by -the wool, as also to add fresh quantities of bran, lime, and -crystallized carbonate of soda, so as constantly to maintain the -fermentation at a suitable point. -</p> - -<p class="c009"> -The German vat differs, then, from the potash vat by the fact that the -potash is replaced by crystallized carbonate of soda and caustic lime, -which latter substance also gives to the carbonate of soda a caustic -character. It presents a remarkable saving as compared to the potash -vat; hence the frequency of its employment; but it requires great -care, and is more difficult to manage. It also offers considerable -economy of labor; one man is amply sufficient for each vat. -</p> - -<p class="c009"> -The army cloth is usually dyed by means of the pastel vat, which gives -the most advantageous results. We here make use of vats about 8½ feet -in depth, and 5 feet in diameter, into which we introduce from 361 -lbs. to 405 lbs of pastel or of woad, after previous maceration. The -vat is to be filled with boiling water, and we then add to the bath 22 -lbs. of madder, 17½ lbs. of weld, and 13 lbs. of bran. The mixture is -to maintained in a state of ebullition for about half an hour; we next -add a few pailsful of cold water, taking care, however, not to lower -the temperature beyond 130° Fah.; during the whole of this time a -workman, provided with a rake, keeps incessantly stirring the -materials of the bath. The vat is then accurately closed by means of a -wooden lid, and surrounded by blankets, so as to keep up the heat. It -is now put aside for six hours; after this time it is again stirred by -means of a rake, for the space of half an hour; and this operation -should be repeated every three hours until the surface of the bath -becomes marked with blue veins; we then add from six to eight pounds -of slaked lime. -</p> - -<p class="c009"> -The color of the vat now borders on a blackish-blue. We immediately -add the indigo in a quantity proportioned to the shade which we wish -to obtain. The pastel in the foregoing mixture may last for several -months; but we must renew the indigo in proportion as it becomes -exhausted, at the same time adding both bran and madder. In general we -employ— -</p> - -<ul> -<li>11 to 13 lbs. of good indigo for 100 lbs. of fine wool.</li> -<li>9 to 11 lbs. of good indigo for 100 lbs. of common wool.</li> -<li>9 to 11 lbs. of good indigo for 131 yards of cloth dyed in the piece.</li> -</ul> - -<p class="c009"> -<span class="smcap">Management of the Vats.</span>—A good condition of the vat is recognized by -the following characters: The tint of the bath is of a fine -golden-yellow, and its surface is covered with a bluish froth and a -copper-colored pellicle. On dipping the rake into the bath, there -escapes bubbles of air, which should burst very slowly; -<span class="pagenum" id="Page_076">76</span> when they -vanish quickly, it becomes an indication that we must add more lime. -The paste which is found at the bottom of the vat, green at the moment -of its being drawn up, should become brown in .the air; if, however, -it remains green, this is a further sign that more lime is required. -Lastly, the vat should exhale the odor of indigo. We usually complete -the assurance of the vat being in a good state by plunging into it, -after two hours’ respite, a skein of wool, which, on being withdrawn -after the lapse of half an hour, should present a green color, but -change directly to blue. We then once more mix the materials of the -vat, and two hours after it may be considered ready for dyeing. -</p> - -<p class="c009"> -These vats, like those already described, are provided with a large -wooden ring, the interior of which is armed with a kind of network, -for the purpose of preventing the objects which are intended to be -dyed coming in contact with the materials at the bottom of the vat; -we, moreover, take the precaution of enclosing the wool or cloth in -bags. These tissues, when plunged into the bath, should remain there -for a longer or shorter time, according to the shade which we wish to -obtain; one dipping, however, will never suffice for this object; -usually we leave in the stuff for half an hour only; it is then to be -taken from the bath, wrung, and exposed to the air. This operation is -repeated until we have succeeded in procuring the desired shade; we -ordinarily suffer three hours to elapse between each dipping. The heat -of the vat should never be allowed to fall below 130° Fah. After each -operation the bath must be well stirred, and fresh lime added; -generally speaking, a pound a day will suffice. We re-establish the -indigo about every second day. When once this vat is well mounted, and -we are careful to examine its working, we may dye from two to four -batches a day with it. -</p> - -<p class="c009"> -When the stuffs have acquired the desired shade, they are first to be -washed in common water, and then in a very weak solution of -hydrochloric acid (about one part in a thousand); after this they are -again rinsed in pure water. -</p> - -<p class="c009"> -The Indian vat is much more easily managed than the foregoing; it -presents less danger of failure, from the fact that it is quickly -exhausted, and also from the fermentative process, which is so -difficult to govern in the pastel vat; this vat not having time to -change in character. It is prepared by first introducing an equal -quantity of madder and of bran, and a triple quantity of potash; this -is to be gradually heated until it reaches a temperature of 167° Fah., -and we then add to it the indigo, thoroughly agitating the matters for -half an hour. The vat is maintained at a temperature of 86° to 100° -Fah., by keeping it closely covered, and at the same time the mixture -is to be stirred occasionally at intervals of twelve hours. It should -by this time present a beautiful green shade, the liquor being -surmounted by a copper-colored pellicle and a purplish froth. We may -now commence the dyeing, following the same course as with the pastel -vat; but the stirrings being here repeated much more frequently than -with the other mixture, we can dye a larger quantity of wool within a -given time. When the vat ceases to give a brilliant blue, we must -altogether renew it; if it be merely weakened, we add to it a small -quantity of freshly prepared liquor containing a few pounds of potash, -and a little less bran and madder. In giving the dark and the clear -sky blues, we must be careful to employ a quantity of indigo -proportioned to the color which we wish to obtain, or, better still, -we may use the previously exhausted vat for the dark blue. -</p> - -<p class="c009"> -When exposed to the influence of the putrid fermentation, indigo is -decomposed and loses its color. If rendered soluble, it obeys the -impulse communicated to the azotized matters with which it is brought -into contact, although, if <span class="pagenum" id="Page_077">77</span> macerated in pure water at the ordinary -temperature, it is itself decomposed with great difficulty. -</p> - -<p class="c009"> -The pastel and the woad are very prone to the putrid fermentation, by -reason of the large quantity of azotized matters which they contain, -as do all the cruciferæ; they require therefore considerable care in -their employment. -</p> - -<p class="c009"> -When a vat is mounted, if the fermentation be allowed to continue -unchecked, after the appearance of the blue froth and the other signs -already indicated, the liquor will acquire a yellow color similar to -that of beer; the froth will become white; it will give out a stale -smell and lose its ammoniacal odor; after a few days it will turn -whitish, and exhale a smell at first similar to that of putrefied -animal substances; then it will acquire the odor of rotten eggs, and -set free sulphuretted hydrogen. The lime in the pastel and the woad -vats, and the tartar-lee and potash in the other mixtures, are used -for the purpose of preventing these accidents. -</p> - -<p class="c009"> -Besides the oxygenated compound, which is formed by the combination of -oxygen with the extractive matters of the plants held in digestion, -there is a production of carbonic acid which saturates the alkaline -lee, and forms a carbonate of lime in the pastel vat. We find this -attached to the sides of the vat in such quantity that the inside of -these vessels becomes incrusted with it to a considerable depth. It is -this product which dyers call the tartar of the vat; it effervesces -with acids, and gives on analysis carbonic acid, lime, and a few -particles of indigo. In the potash vat the solubility of the carbonate -of potash prevents its deposition; but it is very probable that we -have even here a formation of some carbonated products, perhaps in -part formed at the expense of the carbonic acid of the air. -</p> - -<p class="c009"> -The soluble extractive principle being the only matter which remains -in solution in the bath with the indigo, the lime, &c., we have formed -deposits which, varying both in their volume and in the greater or -less facility with which they are precipitated during the various -periods of fermentation, lead to a more or less considerable waste of -time. If we plunge a piece of woollen tissue into a vat which has been -recently stirred, it will acquire a dark color, and will be found -covered with brown stains which are with difficulty removed. When the -woad or paste vat has been stirred, it need be left two or three hours -only before plunging in the stuff, at least during the early months of -its working, inasmuch as the pastel, being but slightly divided and -attenuated, is readily precipitated; but when, by reason of its -extreme division, in consequence of repeated operations, it is thrown -down with less facility, the dipping should not be performed oftener -than three times in the day. -</p> - -<p class="c009"> -The Indian vat requires less time than the others; we may even dye -with it an hour after stirring the mixture. The potash, being soluble, -forms no precipitate; while the ligneous fibre of the madder and the -pellicles of the bran become deposited with great facility. We can -also dip with these vats much oftener than with those made by pastel -or woad. -</p> - -</div> - -<hr class="footnote" /> -<div class="footnote"> -<a id="Footnote_11"></a><a href="#FNanchor_11"> -<span class="label">[11]</span></a> -<p class="c009"> -The distinction between pastel and woad is not very clear. -Schutzenberger says: “Pastel, woad, and satis tinctoria is a <i>plant</i> -of the family of the crucifera. It would seem, however, that the term -<i>pastel</i> as used by the old French dyers is applied to the leaves of -the woad which have been fermented, formed into paste, and afterwards -into balls, and which contain much blue coloring matter. And the term -<i>woad</i> as distinguished from <i>pastel</i> is applied to the unfermented -plant.” -</p> -</div> - -<p><span class="pagenum" id="Page_078">78</span> -</p> - -<h3>SICKNESS OF THE WARM VAT FOR DYEING WOOL, AND ITS REMEDIES.</h3> - -<p class="c009"> -We have to thank that excellent practical magazine, “The American -Chemist,” for the following notes on the sicknesses of the warm vat, -by F. W. Kugler, translated from Reimann’s Färberzeintung:— -</p> - -<div class="c039"> - -<p class="c009"> -In the wool indigo vat, among the principal “sicknesses” is the -blackening of the vat, or “sharpening.” This arises from the presence -of too much lime. When “sharpened,” the liquor, instead of having a -waxy yellow color with a dense blue film on its surface, has no film; -while the liquor is a dark blackish-green, and on being stirred shows -a gray or white scum on its surface, while it emits at the same time a -pungent odor. If the vat is only slightly affected, it is sufficient -to add some bran and madder and to let it stand over night. If it has -not quite recovered by morning, it may be necessary to heat it up, -agitate it, and let it stand for a couple of hours, after which -perhaps the addition of a little lime will be necessary. -</p> - -<p class="c009"> -If the vat is much sharpened, it is recommended to sink in it a bag of -bran, and leave it over night, when the fermentation will have -restored the vat in a considerable degree; but it will be necessary to -add lime cautiously and by degrees, to bring it to a proper state for -working. -</p> - -<p class="c009"> -The theory of the souring of the vat is given. Butyric fermentation -takes place under certain circumstances, butyric acid being formed; -and hydrogen is set free, which reduces the indigo. The addition of -lime makes the vat too strongly alkaline, and sets ammonia free, which -gives the pungent odor of the soured (<i>verschäften</i>) vat. -Simultaneously the lime with the white indigo forms a difficultly -soluble compound, which settles, and thus interferes with the working -of the vat. The excess of lime must be removed, which is accomplished -by introducing bran, which causes a lactic fermentation; and the -lactic acid neutralizes the excess of lime, and destroys the lime -compound with indigo which had been formed. The lime may be -neutralized by the use of mineral acids, but there is danger in that -case of precipitating the indigo. -</p> - -<p class="c009"> -A second “sickness” is “becoming too sweet.” The symptoms are,—the -blue veins and surface film disappear on stirring, the foam gives a -rustling sound, the bath assumes a reddish-yellow color, blue goods -placed in the bath lose their color, and the vat has an unpleasant odor. -</p> - -<p class="c009"> -The vat when “too sweet” needs to be brought to the regular -temperature, and lime to be added cautiously until the vat is brought -to its normal state. It is safer to add an excess of lime and “sour” -the vat, and then bring it back according to the directions under that -head, than to add too little, as less indigo is lost. To use up all -the dye and to dye a light blue, as little lime should be present as -is consistent with the workings of the vat. -</p> - -<p class="c009"> -The cause of the “falling away” of the vat is a too active -fermentation, which produces considerable lactic acid, from which -butyric acid forms, setting free hydrogen, thereby making white -indigo, which, if the action is allowed to continue, changes to a -compound from which the indigo cannot be recovered. If lime is added, -the lactic and butyric acids unite with it and precipitate it, while -the excess precipitates the white indigo, which is slowly recovered, -as fermentation progresses, which forms lactic acid, which, taking the -place of the white indigo, sets it free. Besides the sicknesses, there -are various results of mismanagement, of -<span class="pagenum" id="Page_079">79</span> -which the first is -overwarming, which causes the bath to turn brown, which is the -beginning of the souring. -</p> - -<p class="c009"> -When the bath begins to sour from overheating, some logwood should be -added and then bran, and the vat left to itself over night. The reason -of it is that the temperature is too high for the desired fermentation -to operate. The vat sometimes suddenly turns green, and even when -indigo and the other necessary ingredients are added it remains of -this color. This is called the “breaking up of the vat.” The reason is -that the temperature is too low; to remedy it, it is necessary to add -logwood and bran, warm it up, and stir, when it should stand for some -hours. -</p> - -</div> - -<div class="transnote"> -<h3>Transcriber's Notes</h3> -<ol> -<li>Footnotes have been placed at the end of each associated section.</li> -<li>Obvious typographical errors have been corrected.</li> -<li>Spelling and hyphenation has been made consistent with the most - common usage. Quoted text from other works and authors was left - unchanged.</li> -</ol> -</div> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of Notes Upon Indigo, by John Hayes - -*** END OF THIS PROJECT GUTENBERG EBOOK NOTES UPON INDIGO *** - -***** This file should be named 62008-h.htm or 62008-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/6/2/0/0/62008/ - -Produced by Ronald Grenier. 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