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diff --git a/24016.txt b/24016.txt new file mode 100644 index 0000000..178d458 --- /dev/null +++ b/24016.txt @@ -0,0 +1,4581 @@ +The Project Gutenberg EBook of Photographic Reproduction Processes by P.C. +Duchochois + + + +This eBook is for the use of anyone anywhere 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 http://www.gutenberg.org/license + + + +Title: Photographic Reproduction Processes + +Author: P.C. Duchochois + +Release Date: December 24, 2007 [Ebook #24016] + +Language: English + +Character set encoding: US-ASCII + + +***START OF THE PROJECT GUTENBERG EBOOK PHOTOGRAPHIC REPRODUCTION PROCESSES*** + + + + + +Photographic Reproduction Processes + +A Practical Treatise of the Photo-Impressions Without Silver Salts +By P.C. Duchochois + +New York +The Scovill & Adams Company +423 Broome Street. +1891 + + + + + +CONTENTS + + +INTRODUCTION. +THE DESIGNS. +THE CYANOTYPE OR BLUE PROCESS. +THE CYANOFER. (Pellet's Process.) +THE BLACK OR INK PROCESS. (Ferro-tannate Process.) +THE CUPROTYPE. (Burnett's Process.) +THE ANILINE PROCESS. +THE PRIMULINE OR DIAZOTYPE PROCESS. +TRACING PROCESS ON METAL. +GRAPHOTYPY. +THE URANOTYPE. +THE PLATINOTYPE. + ARTIGUES' PROCESS + THE CARBON PROCESS. + APPENDIX. + + + + + +ILLUSTRATIONS + + +A Tournette +Chardon's method of coating + + + + + +PREPARER'S NOTE + + +Please remember that this book was published over a century ago, long +before today's chemical safety standards. Please get expert advice before +attempting to perform any of the procedures described in this book. + + + + + +AUTHORS QUOTED + + +Artigues. +Bevan, E.J. +Bingham +Borlinetto +Brasseur, Chs. +Buckle. +Burnett, C. J. +Chardon +Cheysson +Colas. +Cooper, H. +Cross, C. F. +De la Blanchere, H. +De St. Florent +Draper, Dr. John +Ducos du Hauron +Dumoulin, E. +Endemann,H. +Fisch, A. +Godefroy. +Green, A. G. +Graubassi +Harman, Alfred. +Herschel, Sir John. +Houdoy +Huebl, Baron. +Hunt, Robert +Liesegang, Dr. L. +Loeffler, J. +Monckhoven, Dr Von. +Niepce, de St. Victor +Obernetter, J. B. +Pellet. +Persoz. +Phipson, Dr. +Pizzighelli, Captain J. +Poitevin, A. +Roy, Paul +Sella, V. J. +Smee, Professor +Stephanowski, Karl. +Swan, J. W. +Willis, William +Wothly, J. +X. + + + + + + +INTRODUCTION. + + +The photographic processes with the salts of iron are all derived from the +researches of Sir John Herschel. The investigations of that great +philosopher are so valuable, so full of instructions that we are led to +reprint them, together with those of Mr. C. J. Burnett, on the salts of +uranium, etc., as an Introduction. It will be seen that the process by +which blue prints are to-day obtained is exactly that Sir John Herschel +devised in 1840. + +"It is no longer an insulated and anomalous affection of certain salts of +silver or gold, but one which, doubtless, in a greater or less degree, +pervades all nature, and connects itself intimately with the mechanism by +which chemical combination and decomposition is operated. The general +instability of organic combinations might lead us to expect the occurrence +of numerous and remarkable cases of this affection among bodies of that +class, but among metallic and other elements inorganically arranged, +instances enough have already appeared, and more are daily presenting +themselves, to justify its extension to all cases in which chemical +elements may be supposed combined with a certain degree of laxity, and so +to speak in a _tottering equilibrium_. There can be no doubt that the +process, in a great majority, if not in all cases, which have been noticed +among inorganic substances, is a deoxidizing one, so far as the more +refrangible rays are concerned. It is obviously so in the cases of gold +and silver. In the case of the bichromate of potash it is most probable +that an atom of oxygen is parted with, and so of many others. A beautiful +example of such deoxidizing action on a non-argentine compound has lately +occurred to me in the examination of that interesting salt, the +ferrosesquicyanuret of potassium described by Mr. Smee in the +_Philosophical Magazine_, No. 109, September, 1840, and he has shown how +to manufacture in abundance and purity, by voltaic action on the common or +yellow ferrocyanuret. In this process nascent oxygen is absorbed, +hydrogen given off, and the characters of the resulting compound in +respect of the oxides of iron, forming as it does Prussian blue with proto +salts, indicate an excess of electro-negative energy, a disposition to +part with oxygen, or which is the same thing, to absorb hydrogen (in the +presence of moisture), and thereby to return to its pristine state, under +circumstances of moderate solicitation, such as the affinity of protoxide +of iron (for instance) for an additional dose of oxygen, etc." + +"Paper simply washed with a solution of this salt is highly sensitive to +the action of the light. Prussian blue is deposited (the base being +necessarily supplied by the destruction of one portion of the acid, and +the acid by the destruction of another). After half an hour or an hour's +exposure to sunshine, a very beautiful negative photograph is the result, +to fix which, all that is necessary is to soak it in water in which a +little sulphate of soda is dissolved. While dry the impression is of a +dove color or lavender blue, which has a curious and striking effect on +the greenish yellow ground of the paper produced by the saline solution. +After washing the ground color disappears and the photograph becomes +bright blue on a white ground. If too long exposed, it gets +'over-sunned,' and the tint has a brownish or yellowish tendency, which, +however, is removed in fixing; but no increase of intensity beyond a +certain point is obtained by the continuance of exposure." + +"If paper be washed with a solution of ammonio-citrate of iron and dried +and then a wash passed over it of the yellow ferro-cyanuret of potassium, +there is no immediate formation of true Prussian blue, but the paper +rapidly acquires a violet-purple color, which deepens after a few minutes, +as it dries, to almost absolute blackness. In this state it is a positive +photographic paper of high sensibility, and gives pictures of great depth +and sharpness, but with this peculiarity, that they darken again +spontaneously on exposure to the air in darkness, and are soon +obliterated. The paper, however, remains susceptible to light, and +capable of receiving other pictures, which in their turn fade, without any +possibility (so far as I can see) of arresting them, which is to be +regretted, as they are very beautiful, and the paper of such easy +preparation. If washed with ammonia or its carbonate, they are for a few +moments entirely obliterated, _but presently reappear with reversed lights +and shades_. In this state they are fixed, and the ammonia, with all that +it will dissolve, being removed by washing in water, their color becomes a +pure Prussian blue, which deepens much by keeping. If the solution be +mixed there results a very dark violet-colored ink, which may be kept +uninjured in an opaque bottle, and will readily furnish by a single wash +at a moment's notice the positive paper in question, which is most +sensitive when wet." + +"It seems at first sight natural to refer these curious and complex +changes to the instability of the cyanic compounds; and that this opinion +is to a certain extent correct is proved by the photographic impressions +obtained on papers to which no iron has been added beyond what exists in +the ferrocyanic salts themselves. Nevertheless, the following experiments +abundantly prove that in several of the changes above described, the +_immediate action_ of the solar rays is not exerted on these salts, but on +the iron contained in the ferruginous solution added to them, which it +deoxidizes or otherwise alters, thereby presenting it to the ferrocyanic +salts in such a form as to precipitate the acids in combination with the +peroxide, or protoxide of iron, as the case may be. To make this evident, +all that is necessary is _simply to leave out the ferrocyanate_ in the +preparation of the paper, which thus becomes reduced to a simple washing +over with the ammonio-citric solution. Paper so washed is of a bright +yellow color, and is apparently little, but in reality highly sensitive to +photographic action. Exposed to strong sunshine, for some time indeed, its +bright yellow tint is dulled into an ochrey hue, or even to gray, but the +change altogether amounts to a moderate percentage of the total light +reflected, and in short exposures is such as would easily escape notice. +Nevertheless, if a slip of this paper be held for only four or five +seconds in the sun (the effect of which is quite imperceptible to the +eye), and when withdrawn into the shade be washed over with the +ferrosesquicyanate of potash, a considerable deposit of Prussian blue +takes place on the sunned part, and none whatever on the rest; so that on +washing the whole with water, a pretty strong blue impression is left, +demonstrating the reduction of iron in that portion of the paper to the +state of protoxide. The effect in question is not, it should be observed, +peculiar to ammonio-nitrate of iron." + +"The ammonio and potasso-tartrate fully possess and the perchloride +_exactly neutralized_ partakes of the same property; but the experiment is +far more neatly made and succeeds better with the other salts." + +"The varieties of cyanotype processes seem to be innumerable, but that +which I shall now describe deserves particular notice not only for its +pre-eminent beauty while in progress, but as illustrating the peculiar +power of the ammoniacal and other parsalts of iron above-mentioned to +receive a latent picture susceptible of development by a great variety of +stimuli. This process consists in simply passing over the +ammonio-citrated paper on which such a latent picture has been impressed, +_very sparingly and evenly_, a wash of the solution of the common yellow +ferrocyanate (prussiate) of potash. The latent picture, if not so faint +as to be quite invisible (and for this purpose it should not be so), is +negative. As soon as the liquid is applied, which cannot be in too thin a +film, the negative picture vanishes, and by very slow degrees is replaced +by a positive one of a violet blue color on a greenish yellow ground, +which at a certain moment possesses a high degree of sharpness and +singular beauty and delicacy of tint. If at this instant it be thrown +into water, it passes immediately to a Prussian blue, losing, at the same +time, however, much of its sharpness, and sometimes indeed becoming quite +blotty and confused." + +"To prevent this confusion gum arabic may be added to the prussiated +solution, by which it is hindered from spreading unmanageably within the +pores of the paper, and the precipitated Prussian blue allowed time to +agglomerate and fix itself on the fibers. By the use of this ingredient +also, a much thinner and more equal film may be spread over the surface, +and _when perfectly dry_, if not sufficiently developed, the application +may be repeated. By operating thus I have occasionally (though rarely) +succeeded in producing pictures of great beauty and richness of effect, +which they retain (if not thrown in water) between the leaves of a +portfolio, and have a certain degree of fixity--fading in strong light and +recovering their tone in the dark. * * *" + +"If paper be washed with a mixture of the solutions of ammonio-citrate of +iron and ferrosesquicyanate (red prussiate) of potash, so as to contain +the two salts in about equal proportions, and being then impressed with a +picture, be thrown into water and dried, a negative blue picture will be +produced. This picture I have found to be susceptible of a very curious +transformation. To effect this it must be washed with a solution of +protonitrate of mercury, which in a little time entirely discharges it. +The nitrate being thoroughly washed out and the picture dried, a smooth +iron is passed over it, somewhat hotter than is used for ironing linen, +but not sufficiently so to scorch or injure the paper. The obliterated +picture immediately reappears, not blue, but brown. If kept for some weeks +in this state between the leaves of a portfolio, in complete darkness, it +fades, and at length almost disappears. But what is very singular, a +fresh application of heat revives and restores it to its full intensity." + +"This curious transformation is instructive in another way. It is not +operated by light, at least not by light alone. _A certain temperature_ +must be attained, and that temperature suffices in complete darkness. +Nevertheless, I find that on exposing to a very concentrated spectrum +(collected by a lens of short focus) a slip of paper prepared as above +(that is to say, by washing with the mixed solutions, exposure to +sunshine, washing and discharging the uniform blue color so induced, as in +the last article), its whiteness is changed to a brown over the whole +region of the red and orange rays, _but not beyond_ the luminous spectrum. +Three conclusions seem unavoidable: first--that it is the heat of these +rays, not their light, which operates the change; second--that this heat +possesses a peculiar chemical quality which is not possessed by the purely +calorific rays outside of the visible spectrum, though far more intense; +and third--that the heat radiated from obscurely hot iron abounds +especially in rays analogous to those of the region of the spectrum above +indicated." + +Sir John Herschel then proceeds to show that whatever be the state of the +iron in the double salts in question, its reduction by blue light to the +state of protoxide is indicated by many other agents. "Thus, for +example," says Robert Hunt, "if a slip of paper prepared with the +ammonio-citrate of iron be exposed partially to sunshine, and then washed +with the bichromate of potash, the bichromate is deoxidized and +precipitated upon the sunned portion, just as it would be if directly +exposed to the sun's rays." + +"I have proved this fact with a great number of preparations of cobalt, +nickel, bismuth, platinum and other salts which have been thought hitherto +to be insensitive to the solar agency; but if they are partially sunned +and then washed with nitrate of silver and put aside in the dark, the +metallic silver is slowly reduced upon the sunned portion. In many +instances days were required to produce the visible picture; and in one +case paper being washed in the dark with neutral chloride of platinum was +sunned and then washed in the dark with nitrate of silver; it was some +weeks before the image made its appearance, but it was eventually +perfectly developed, and, when quite so, remained permanently impressed +upon the paper." + +The following process, discovered at the same time as the cyanotype, and +termed chrysotype, is thus described by Sir John Herschel: + +"In order to ascertain whether any portion of the iron in the double +ammoniacal salt employed has really undergone deoxidation, I had recourse +to a solution of gold, exactly neutralized by carbonate of soda. The +proto-salts of iron, as is well known to chemists, precipitate gold in the +metallic state. The effect proved exceedingly striking, and, as the +experiment will probably be repeated by others, I shall here describe it +ab initio. Paper is to be washed with a moderately concentrated solution +of ammonio-citrate of iron and dried. The strength of solution should be +such as to dry into a good yellow color, not at all brown. In this state +it is ready to receive a photographic image, which may be impressed on it +either from nature in the camera obscura, or from an engraving on a frame +in sunshine. The image so impressed is, however, very faint, and +sometimes hardly perceptible. The moment it is removed from the frame or +camera, it must be washed over with a neutral solution of chloride of gold +of such strength as to have about the color of a sherry wine. Instantly +the picture appears, not, indeed, at once of its full intensity, but +darkening with great rapidity up to a certain point, depending on the +strength of the solutions used, etc. At this point nothing can surpass +the sharpness and perfection of detail of the resulting photograph. To +arrest this process and to fix the picture (so far at least as the further +agency of light is concerned), it is to be thrown into water very slightly +acidulated with sulphuric acid, and well soaked, dried, washed with +hydrobromate of potash, rinsed and dried again. * * *" + +"In point of _direct_ sensibility, the chrysotype paper is certainly +inferior to the calotype; but it is one of the most remarkable +peculiarities of gold as a photographic ingredient, that _extremely feeble +impressions once made by light go on afterwards, darkening spontaneously +and very slowly, apparently without limit so long as the least vestige of +unreduced chloride of gold remains in the paper_. To illustrate this +curious and (so far as applications go) highly important property, I shall +mention incidentally the results of some experiments made during the late +fine weather on the habitudes of gold in presence of oxalic acid. It is +well known to chemists that this acid, heated with solutions of gold, +precipitates the metal in its metallic state; it is upon this property +that Berzelius has founded his determination of the atomic weight of gold. +Light, as well as heat, also operates this precipitation; but to render it +effectual, several conditions are necessary:--First--the solution of gold +should be neutral, or at most _very_ slightly acid; secondly--the oxalic +acid must be added in the form of a neutral oxalate; and thirdly--it must +be present in a certain considerable quantity, which quantity must be +greater the greater the amount of free acid present in the chloride. +Under this condition, the gold is precipitated by light as a black powder +if the liquid be in any bulk; and if merely washed over paper, a stain is +produced, which, however feeble at first, under a certain dosage of the +chloride, oxalate and free acid, goes on increasing from day to day and +from week to week, when laid by in the dark and especially in a damp +atmosphere, till it acquires almost the black of ink; the unsunned portion +of the paper remaining unaffected, or so slightly as to render it almost +certain that what little action of the kind exists is due to the effect of +casual dispersed light incident in the preparation of the paper. I have +before me a specimen of paper so treated in which the effect of thirty +seconds' exposure to sunshine was quite invisible at first, and which is +now of so intense a purple as may be well called black, while the unsunned +portion has acquired comparatively but a slight brown. And (what is not a +little remarkable, and indicates that in the time of exposure mentioned +the _maximum_ of effect was attained) other portions of the same paper +exposed in graduated progression for longer times, viz., one minute, two +minutes, and three minutes, are not in the least perceptible degree darker +than the portion on which the light has acted during thirty seconds only." + +"If paper prepared as above recommended for the chrysotype, either with +the ammonio-citrate or ammonio-tartrate of iron, and impressed, as in that +process, with a latent picture, be washed with nitrate of silver instead +of a solution of gold, a very sharp and beautiful picture is developed of +great intensity. Its disclosure is not instantaneous; a few moments +elapse without apparent effect; the dark shades are then first touched in, +and by degrees the details appear, but much more slowly than in the case +of gold. In two or three minutes, however, the maximum of distinctness +will not fail to be obtained. The picture may be fixed by the +hyposulphite of soda, which alone, I believe, can be fully depended on for +fixing argentic photographs." + +"The best process for fixing the photographs prepared with gold is as +follows: As soon as the picture is satisfactorily brought out by the +auriferous liquid, it is to be rinsed in spring water, which must be three +times renewed, letting it remain in the third water five or ten minutes. +It is then to be blotted off and dried, after which it is to be washed on +both sides with a somewhat weak solution of hydriodate of potash. If +there be any free chloride of gold present in the pores of the paper it +will be discolored, the lights passing to a ruddy brown; but they speedily +whiten again spontaneously, or at all events on throwing it (after lying a +minute or two) into fresh water, in which, being again rinsed and dried, +it is now perfectly fixed." + +As the chrysotype will be no more referred to, we shall state, first, that +the image can be developed with a plain solution of silver nitrate or one +acidified with citric or any other organic acid, which generally gives a +brown impression that can be toned with an acid or alkaline gold bath, the +color varying with the solution employed; and secondly, that the process +may be employed to obtain outlines of any picture on paper or canvas to be +colored in oil-paints. The impression developed with gold terchloride is +pale blue, _quite permanent_, and does not at all interfere with the work +of the artist. The canvas should first be washed with a mixture of +alcohol and aqueous ammonia, then dried and rubbed with pumice stone +powder to give a _tooth_. The modus operandi suggests itself. + +The researches of Mr. C. J. Burnett on the application of uranium salts +and other compounds to photography are recorded in the _Photographic +Notes_ of Ths. Sutton for 1857. We give in the following lines the most +interesting parts of the two papers of Mr. Burnett: + +* * * "The next class of processes are dependent on the sensitiveness to +light of the salts of uranic oxide or sesquioxide of uranium, U2O3." + +"In the first process, the paper being charged with the uranic salt and +exposed to the solar influence under the negative to be copied, is washed +with a solution of the ferridcyanide or red prussiate of potash. The +'Harvest Scene' in the exhibition, being from an albumen negative lent me +by Mr. Ross, the well-known Edinburgh photographer, is an example, the +salt of the sesquioxide of uranium being in this case the hydrofluate, and +the time of exposure from the strength of the albumen negative fully an +hour of good sunshine. I have used for the solution of the uranic oxide +for this process a variety of acids with very similar results; the +sensitiveness of the prepared paper to light varying much, however. For +instance, a collodion negative with the hydrofluate paper producing a very +good print in half an hour of unsteady sun, while with a paper prepared +with the tartaric acid solution of the oxide, it gave an equally good +impression in less than five minutes of the same intermitting sunshine, +indicating thus a difference of sensitiveness of six to one in favor of +the tartrate." + +"The rationale of this process is the reduction of the sesqui-oxide of +uranium, U2O3, on those parts of the paper exposed to the solar influence, +to a lower state of oxidation, the photo-oxide UO, the salts of which have +the property of forming with soluble alkaline ferridcyanides a rich +chocolate-brown precipitate, while the salts of the sesquioxide are +destitute of this reaction. Hence the brown deposit on the parts of the +picture on which the sun has been allowed to act when the developing +solution is applied, and the absence of any such appearance on those parts +which have been protected from its influence." + +"As to the manipulatory details of this process, the paper is floated on +the solution in a dark room and hung up to dry, and then preserved from +light in a portfolio. If carefully secluded from light it appears to keep +well. After exposure for the proper time under this negative, there is in +some cases scarcely any visible impression; while in other cases, +particularly when using the tartaric solution, I have found the impression +very distinguishable, of a brownish or blackish shade, although still +quite faint. The development is best conducted by floating it, anything +like rubbing the picture being very objectionable." + +"When the picture has fully come out, which is generally from three to ten +minutes at the very most, it is removed from the developing bath, placed +in cold water and washed very gently for a few minutes, the water being +frequently changed till it ceases to acquire a yellow tinge from the +dissolved red prussiate. The picture is then drained from the water, +pressed between folds of blotting paper, dried (I dry in the dark), and +the process is complete. * * * I may state, as one recommendation of this +process to ladies and other lovers of clean hands, that any brown stains +left by it on the fingers or elsewhere are at once removable by a little +weak ammonia or soap and water. * * * I would particularly suggest, as +deserving of notice, the development of the salts of sesquioxide of +uranium, and still more iron, by the metals and metallic-cyanic alkaline +salts, as also by the mellonides and nitro-prussides, and the latter also +by itself and as developed by many metallic salts." + +"I have since had the opportunity of trying the nitro-prusside of sodium, +which, by itself, gives a blue and white picture, in color like that +obtained from the red prussiate of potash." + +"When mixed with a solution of ammonio-nitrate of copper, previous to its +application to the paper, the color obtained is pale purplish pink or +peach-blossom color. By mixing it in the same way with ammonio-oxalate of +sesquioxide of iron, we get a dull green picture, changeable through +intermediate stages into brown by alkaline carbonates, and that into a +_dirty_ black by gallic acid. It may be well to know that the blue of the +picture given by the red prussiate in the process of Sir John Herschel may +be considerably modified or entirely changed to another color, in many +ways, without interfering with the purity of the white ground, by steeping +the picture, after the undecomposed red prussiate has been washed out, in +solution of salts of various metals, copper, uranium or cobalt, for +instance, and that the colors so produced may be modified as desired, +according to the stage at which the action is stopped." + +"There remains but one class of uranic photographs to be described, +namely, that obtained when we develop with a salt of silver or gold (or +platinum?). This class may be made to print much more rapidly than our +ordinary silver printing process, approaching sometimes more nearly to the +calotype development in this respect. We get the _minutest details_ with +great fidelity, and the picture is effectually fixed by a simple fresh +hyposulphite solution, with a good color in many cases, or by ammonia, +which will be considered an advantage by those who hold the hyposulphite +an enemy to durability. Different shades of color are produced according +to different solvent acids and different details. I have got a good black +perfectly like that of an engraving, by the nitrate of uranic oxide, +developed by ammonio-nitrate of silver (or plain nitrate) and fixed by +plain hyposulphite without any coloring bath. * * * I have tried the +hyposulphite of gold on some of the silver-developed prints prepared with +the hydrofluate of the uranic oxide and fixed with ammonia, which had an +exceedingly unpleasant raw-red color, a very agreeable gray was at once +obtained. I have succeeded in getting very beautiful impressions by +development of the uranic paper by chloride of gold alone." + +In another communication to the _Photographic Notes_, more interesting +perhaps than the foregoing, Mr. Burnett says: + +"The clearest and brightest of my results have been obtained by the action +of gallic acid, tannin, or especially a _mixture of tannin and carbonate +of ammonia_, potash or soda, on the blue pictures obtained by the +solarization of paper prepared with ferridcyanide of potassium, +ferrocyanide or ferridcyanide of ammonium. * * * I have also experimented +with the bichromate and iron, with gallic, tannin and other developer; but +I must confess to not having been, in this particular way, so successful +as Mr. Sella appears to have been in the preservation of the whites, owing +possibly to my not having taken the trouble to wash out sufficiently the +iron before toning."(1) + +"I have experimented most extensively in many ways with the chromates and +bichromates, and have succeeded in various ways in getting _very good_ +results. A very capital process for many purposes is to float or steep +your paper in a mixed solution of bichromate of potash and sulphate of +copper. As for E. Hunt's chromotype process," (2) I have mixed gelatine, +or occasionally grape sugar, or both, with the solution, but instead of +developing it by a silver solution, as in the chromotype, wash out the +salts unacted on by light, and develop by floating on a solution of +ferrocyanide of potassium. The color of the red copper salt which now +forms the picture may be modified or changed in many ways, viz., by +soaking the picture, after the ferrocyanide of potassium has been washed +out of the lights, in a solution of sulphate of iron (or the iron salt +may, but not so advantageously, have been applied to the picture before +the application of the ferrocyanide). Solutions of chloride of tin, +gallic and tannic acids, alone or with alkalies or alkaline carbonates, +may also be employed to modify or change the color. Instead of developing +by ferrocyanide you may develop by the cobalt or chromo-cyanogen salts, or +by an alkaline _mellonide_ arsenite, etc. Sulphureted hydrogen, or a +sulphide, will give a _brown_, or _black_ tone, which may be protected +against oxygen and dampness by a resinous varnish. + +"Of all the simple pictures obtainable with bichromated papers, without +complications or other tonings, those obtainable by the combination of a +salt (say the sulphate) of _manganese_, with the bichromate in the paper +preparation, are about the best; these pictures being, however, capable of +being toned and modified in many different ways if desired. This may be +accomplished by the use of toning baths of ferridcyanide or ferrocyanide, +or other metal cyanogen salts, etc., or by either mixing the salts of +other metals, as copper or iron, with the cyanic toning baths, or using +them in the original solution, or by soaking the paper in them, as in +Sella's process, previously to the application of the metal cyanic, +mellonic or other toning baths. Alkalies and alkaline carbonates may also +be used to remove the chromic acid, and leave a subsalt, or the very +stable oxide or carbonate of manganese, which may be peroxidized by the +use of chloride of lime, peroxide of hydrogen, or ozone." + +"In all the processes with metallic salts, alone with bichromates, the use +of sized or unsized paper along with gelatine, etc., has some advantages. +I have got good results by such processes on albumen paper, the albumen +tending to prevent mealiness in the print; also on paper soaked in +gelatine before the application of the bichromic solution. * * * There is +great interest connected with the action of all such papers, along with +the tannin and vegetable coloring matters. I have long been of opinion +that by the steeping of papers or textile fabrics, containing the salts +not only of iron, as recommended by Mr. Sella, but of tin, copper, +bismuth, lead, etc., in solutions of cochineal, red cabbage, beetroot, +grass or the most ordinary foliage, etc., that the most useful results +might be obtained; though for _certain_ permanence I am not sure but that +some of the other processes which I have briefly run over with the +cyanogen acid salts or metallic acid salts, as precipitators, may be more +to be depended upon. The processes with _precipitated oxides_, such as +the one with manganese and similar ones, with other metals which I have +described, I also consider as deserving of more attention than almost any +processes which have been stated, on the score of probable permanence; but +perhaps the best process for black, or generally useful neutral tint, +without silver, that has yet been offered to the public, I believe to be +the process alluded to with the bichromate of potash and sulphate of +copper, toned by an iron salt. * * * This process, the cuprotype (as +also the uranotype and manganotype) is applicable perfectly to films of +_albumen_ or gelatine on glass or porcelain, textile fabrics, parchment, +paper, tiles and many other substances besides paper." + + + + + +THE DESIGNS. + + + + + HOW TO MAKE A NEGATIVE DRAWING + + +The drawing paper for designs to be reproduced by the cyantotype and the +other processes described in this book should be of a fine texture, free +from opacities and very white; and, as the design must serve as a cliche +it is a sine qua non that it be drawn with a very black ink and with +well-fed lines, especially those which are very fine. To obtain a +complete opacity, and, at the same time, to keep the ink quite fluid, +which gives great facility to the designer, one adds some gamboge (or +burnt sienna) to the India ink. The ink of Bourgeois, which is compounded +with yellow and can be diluted as easily as India ink, is excellent, so is +also the American ink of Higgins.(3) + +As much as possible it is desirable to replace the colored lines +indicating the constructions, the axis, projections, etc., by differently +punctuated lines made with India ink. However, if the use of colors be +obligatory on the original design, one should trace the red lines with +very thick vermilion or sienna, the yellow lines with gamboge, and the +blue and green lines with a thick mixture of Prussian blue and chrome +yellow in different proportions. + +One must abstain from applying washes of any tints on the original. If +necessary they should be brushed over when the reproductions are made; +moreover they can be often replaced by cross-lines more or less open, and +the shadowing represented by thicker but not closer lines. + +Tracing paper is recommended instead of linen, which latter, on account of +its thickness and granulation, gives less satisfactory results in regard +to the transparency of the ground and the continuity of the lines. + +To reproduce a design on ordinary paper--not too thick--or an engraving, +etc., the paper is rendered transparent by rubbing over on the back of the +original a solution of 3 parts in volume of castor oil in 10 parts of +alcohol, by means of a small sponge. When the paper is quite transparent, +the oil in excess is removed by pressure between sheets of blotting paper, +and the paper dried before the fire or spontaneously. The design so +treated is not in the least injured, for it assumes its primitive +condition by dissolving the oil from the paper by immersion into strong +alcohol, which it is necessary to renew once or twice, then rinsing in +alcoholized water if the drawing be in India ink, or simply in water in +the case of an engraving, and finally drying between sheets of blotting +paper. + +Instead of an alcoholic solution of castor oil, vaseline can be employed. +The paper is more transparent. + +The method by which are made negative drawings, that is, those which can +be used as negative cliches to reproduce the design in black lines on a +white ground, is thus described by Mr. Cheysson, wlio originated it, in a +manual published by the Department of Public Works of France, from which +we have borrowed most of the above instructions for the drawing of designs +suitable for the photo-reproduction processes:(4) + +"One can avoid the necessity of making a negative from the original +drawing by transforming the drawing itself into a negative." + +"To that effect it suffices to draw with lithographic ink, then to cover +the paper with aniline brown, and, after drying, to wash it with +turpentine oil which dissolves the lithographic ink without altering the +aniline. The lines appear then white on a brown ground impervious to +light (that is, non-actinic). The design is thus transformed into a +negative, and can yield positive impressions with paper sensitized with +silver salts, the ferriprussiate or the bichromate of potash. The +lithographic ink should be very black and the lines well fed." + +"When the drawing is finished it is placed on a board lined with sheets of +blotting paper, then one spreads all over it the aniline brown with a +brush, and, lastly, after drying, the paper is carefully rubbed with a +bung of cotton or a rag imbued with turpentine until the lines of the +design are dissolved." + +In our practice we have often taken a negative cliche from drawings made +in the ordinary manner, without the aid of the camera obscura (which would +have been too expensive for drawings of a certain size), by simply +printing a proof by contact on plain or albumenized silvered paper, and +fixing, without toning, in a new solution of sodium thiosulphate, then +washing as usual. The proofs thus obtained from designs drawn with an +opaque ink, which allows a long insulation and, therefore, yields an +intense reduction, are of a deep brick-red color, quite non-actinic, and +give very good positives by the Artigues process. + +N.B.--Paper in drying never assumes its original shape; it is, therefore, +necessary to make the figures on the reproductions from plans when they +are not on the originals. + + + + + CHOICE OF PAPER. SIZING. + + +In all the photographic processes by precipitation of metallic oxides the +quality of the paper has a great influence on the results. When the paper +is not well sized and not well calendered, the sensitizing solution is +absorbed, instead of simply impregnating the surface of the paper, and not +only the image is sunk in and its sharpness impaired, but good whites can +never be obtained, especially if the image should be toned, owing to the +impossibility of eliminating the metallic salts not acted on, that is, not +reduced by the action of light which the fibers of the paper mechanically +retain. + +The "endless" rolls of paper, 54: inches wide--or "blue print paper," as it +is sometimes termed--of Blanchet freres et Kleber, of Rives, better known +as "Rives' paper", that of Johannot, of Annonay (France), and the +Steinbach (Saxe) paper are recommended. + +For small prints from negatives in half tone the positive paper, 18x22 +inches, of Rives or Saxe, should be preferred to the heavy kind. It is +advisable to size it, so that the impressions be entirely formed on the +surface of the paper. Moreover, an additional sizing is always +advantageous, whatever be the photographic process employed, to prevent +the imbibition of the sensitizing compound and to obtain more brilliant +and vigorous images, for the iron, chromium, uranium and other metallic +soluble salts require the presence of an organic matter (alcohol, ether, +gum arabic, glucose, caseine, etc.) to be reduced by the agency of light; +and as a consequence, the greater, within certain limits, of course, the +amount of organic matters, and the more thoroughly they are mixed with the +salts, the more sensitive the preparation and the better the results. + +Arrowroot is the best sizing for our purposes. Gelatine may be employed, +albumen also, but the coating should be insolubized when applied on the +paper and dry. + +_Sizing with Arrowroot._--In a porcelain dish diffuse 4 parts of powdered +arrowroot and one part of liquid glucose in 200 parts of distilled or rain +water and dissolve by heat over an alcohol lamp, stirring all the while. +Let the solution boil for an instant, and when the paste is homogeneous +let it cool down and then remove the skin formed on its surface and strain +it through a fine canvas. Now provide with three small sponges free from +gritty matters and cleaned in water, and nail by the four corners, one +over the other, felt size uppermost, as many sheets of paper as you wish +to size on a board somewhat smaller than the paper. This done, with one +of the sponges take a small quantity of the arrowroot and, brushing it +length-way and cross-way, spread the paste into an even layer, then, by +rubbing very lightly with the second sponge, efface the striae and smooth +the coating as well as possible. The third sponge serves to remove the +excess of paste when too much is at first spread on. From six to seven +sheets of paper, 18x22, can be sized with the quantity of arrowroot paste +above given. + +Another, but not quite so effective a manner of sizing although sufficient +for the cyanotype, is the following, employed by Mr. Pizzighelli for the +paper used in the platinotypic process: + +Ten parts of arrowroot are powdered in a mortar with a little water and +then mixed by small quantities to 800 parts of boiling water. After a few +minutes 200 parts of alcohol are added and the mixture filtered. The +paper is immersed for two or three minutes in the warm solution and hung +up to dry. + +_Sizing, with Gelatine._--Dissolve at a temperature of about 140 deg. Fahr. +(60 deg. C.) 10 parts of good gelatine in 800 parts of water, then add 200 +parts of alcohol and 3 parts of alum dissolved in a little water. Filter +and prepare the paper by immersion as above directed. The gelatinized +paper when dry should be prepared a second time and dried by hanging it up +in the opposite direction in order to obtain an even coating. + + + + + +THE CYANOTYPE OR BLUE PROCESS. + + +_This process gives white impressions on a blue ground with diapositives +or drawings on transparent or semi-transparent materials, and blue +impressions on a white ground from negatives._ It is commonly known under +the names of "blue print process," "negative ferrotype process" and +"ferro-prussiate process." + +The process is indeed exceedingly simple. A sheet of paper, impregnated +or sensitized, as it is termed, with a solution of ferric citrate and +ferricyanate is impressed under a cliche,(5) then immersed in pure water, +whereby the image is developed and at the same time fixed. It is on +account of the great advantages offered by its simplicity that this +process is generally preferred by civil engineers and architects for the +reproduction of their plans. + +The sensitizing solution is prepared in mixing by equal volumes the two +solutions following: + +A. Iron, ammonio 20 parts + citrate + Water 100 parts +B. Potassium 15 parts + ferricyanate (red + prussiate) + Water 100 parts + +Although the mixture keeps pretty well for a certain period in the dark, +it is best to prepare only the quantity wanted for actual use.(6) + +The paper is preferably sensitized in operating as follows: + +Take hold of the paper by the two opposite corners and fold it into a +loop, lay it on the iron solution, the center of the sheet first placed in +contact with the liquid, and then gradually spread it by lowering the +corners with a little pressure. No solution should run over on the back +of the paper; it would be a cause of stain. This done, and without +allowing the liquid to penetrate _in_ the paper, immediately take hold of +the two corners near the body and withdraw the paper by dragging it over +on a glass rod for this purpose fixed on the edge of the tray. Now pin up +the paper to dry, which should be done rapidly, and sensitize a second +time in proceeding in the same manner. If this second sensitizing be +found objectionable, let float the paper for no more than ten seconds; of +course this method of sensitizing is not applicable to prepare larger +sheets of paper. In this case the paper is pinned by the four corners on +a drawing board or any other support, lined with blotting paper and +quickly brushed over with a sponge sparingly imbued with the sensitizing +mixture, so as to wet the paper with a very small excess of liquid. + +The rationale of this manner of sensitizing is to impregnate only the very +surface of the paper with the ferric salts, and thereby to obtain an +intense blue with very good whites, which latter it would be impossible of +obtaining should the sensitizing solution be allowed to reach in the +fibers of the paper, for, in this condition, it is impossible, owing to +the exigencies of the process, to wash out thoroughly the iron salts to +prevent the chemical changes which cause the whites to be tinted blue. It +is for this reason that better results are also obtained with well sized +papers. + +The sensitizing should be done by a very diffused daylight, and the +drying, of course, in a dark room. When sensitized the paper is yellowish +green. It should be well dried for keeping, and rolled or wrapped in +orange or brown paper and preserved from the action of dampness and of the +air. It does not keep well, however, no more than two or three months, +perhaps, in good condition; but the sooner it is employed the finer the +proofs, the better the whites and more rapidly is the paper impressed. + +There is in the market a paper which keeps for a long time. It is +prepared by adding a small quantity of gum arabic or of dextrine to the +sensitizing solution. Good for the reproduction of line work, it does not +give very satisfactory results for pictures in half tones. + +The following compound gives a paper much more sensitive, but not keeping +so long, than that prepared according to the formula previously given: + +Tartaric acid 25 parts +Ferric chloride, solution 80 parts (in volume) +at 45 deg. Baume +Water 100 parts + +When the acid is dissolved, add gradually concentrated aqueous ammonia, +just enough to neutralize the solution--170 volumes, about. The chemical +change consists in the formation of ferric tartrate. Let cool the +solution, then, after adding the following, keep it in the dark: + +Potassium ferricyanate 211/2 parts +Water 100 parts + +Another and very sensitive preparation is the following: + +A. Iron perchloride, 40 parts + cryst + Oxalic acid 10 parts + Water 100 parts +B. Potassium 20 parts + ferricyanate + Water 100 parts +Mix + +_Printing._--The process we describe yields negative impressions, that is a +positive image from a negative cliche, and a negative image from a +positive cliche, exactly as the silver printing-out process ordinarily +employed in photography. Consequently, for the production of non-reversed +proofs from plans, etc., the original drawing should be placed _face +downwards_ on the glass plate of the printing frame, and, upon the back, +the sensitive paper is laid and pressed into perfect contact by means of a +pad, felt or thick cloth. + +The printing frame is that used by photographers. The lid is divided, +according to the side, in two, three and even four sections, held by +hinges and fastened for printing by as many cross-bars, in order that by +opening one section, from time to time, the operator can follow the +progressive changes resulting from the action of light on the iron salts. +To print, the frame should be placed in the light in such a manner as the +luminous rays fall perpendicularly upon the drawing or cliche. The reason +of this is obvious, since the sensitive paper is not in direct contact +with the design, but separated by the material upon which it is drawn. + +During the insolation--whose time depends necessarily from the more or less +transparency of the cliche, and, also, from the intensity of the +light(7)--the paper assumes first a violet tint, which gradually +intensifies to a dark shade; then this tint fades, becomes brownish, then +pale lilac, while the parts under the lines--that is, the design--upon which +the light has, therefore, no action, are visible by keeping the original +yellow-green tint of the prepared paper. It is when the lilac color is +produced that the exposure is sufficient. + +To ascertain when the exposure is correct, a few black lines can be traced +on one of the edges of the margin of the design, and strips of the +sensitive paper placed upon them to serve as _tests_ in operating, as it +will be explained in the description of the Cyanofer process. When one of +them is taken out and show, by being washed in water, a clear white line +on a deep blue ground, the exposure is at an end. One understands that +the blue color of the ground is more or less intense according to time of +insolation, for the chemical actions between the reduced and the +non-reduced iron salts is so much more complete as the salts acted on are +more or less deoxidized, that is, reduced to ferrous salts; and that to +obtain the maximum of effect, which, therefore, depends on the allowable +time of exposure, the drawing ink should be opaque and non-actinic as far +as possible, because when, on testing, the lines are tinted the exposure +should be discontinued. However, a slight coloration of the lines is not +very objectionable, for it disappears by a longer washing after the +development. + +The image is developed and fixed by washing in water two or three times +renewed. The water must be free from calcareous salts; these salts +converting the iron into carbonates which impart an ochrey tinge to the +proof. Rain water--any water in which no precipitate is thrown down by +the addition of a few drops of a weak solution of silver nitrate--may be +used with safety. + +During the development the ground takes a blue color which rapidly +intensifies, while the iron compound, not acted on and imparting a yellow +green tint to the design, is washed out from the white paper. If the +print has not been sufficiently exposed the ground remains pale blue, more +or less; the reason has been explained. In this case the development +should be done quickly, as the blue is always discharged by washing. On +the other hand, whenever the whites are tinted by excess of exposure, they +can be cleared partly or entirely by a prolonged immersion in water, but +the ground is also to some extent lightened. + +When the proof is well developed and fixed, that is, when the soluble iron +salts are eliminated, the blue color can be brightened by adding to the +last but one washing water a small quantity of citric acid, or of +potassium bisulphate, or a little of a solution of hypochlorite of lime +(bleaching powder). + +The action of light in this, as well as in the other photographic +processes with metallic salts described in this work, is one of +deoxidation, as shown by Herschel. The chemical changes which produce the +blue precipitate is quite complicated. It is evident that both the ferric +citrate and the ferric cyanate are partly reduced to ferrous salts under +the luminous influence, and react in presence of water with the unreduced +part of each of these compounds, the ferric citrate with the ferrous +cyanate forming Prussian blue (ferric-ferrocyanate), and the ferric +cyanate with the ferrous citrate giving rise to Turnbull's blue (ferrous +ferricyanate). The blue of the print is consequently a mixture in a +certain proportion of the two compounds; and as the color of Prussian blue +is quite different from that of Turnbull's, it follows that by varying in +a certain measure the percentage of the two ferric salts forming the +sensitizing solution, the color of the blue may be varied thereby. Hence +the difference in the formulas given by different authors.(8) + +The blue color of the image can be changed into black or dark green. But +to that purpose the paper should be, although not exactly necessary, well +sized as before directed, and sensitized with extra care to prevent the +imbibition of the iron solution into the paper. After exposure the proof +should necessarily be thoroughly washed to eliminate the soluble iron +salts, then immersed for a moment in water acidified with nitric acid, +1:100, and this done and without washing treated by a solution of aqueous +ammonia at 2 per 100 of water. In this the blue color disappears, being +changed into a red brownish tint, which indicates that the Turnbull's and +Prussian blues are transformed, the former into ferroso-ferric hydrate, +with formation of ferrocyanate, and the latter into ferric hydrate. It is +by the action of tannin (gallotannic acid) on the ferric oxides thus +formed that the black is produced, and by that of catechu-tannic acid +contained in the extract of catechu that one obtains a dark green, almost +black color. + +To obtain the black tone it suffices to immerse the proof on its removal +from the ammoniacal in a solution of tannin at 5 per 100 of water, and +when toned, to wash it in a few changes of water. + +The process to turn the blue color into a green was devised by Mr. Paul +Roy. It is as follows: Dissolve 7 parts of borax in 100 parts of water, +and acidify the solution with sulphuric acid added drop by drop until the +litmus paper becomes red; then, in the same manner, neutralize with +aqueous ammonia not in excess, but just enough to show an alkaline +reaction; this done dissolve 1 part of powdered catechu and filter. In +this the proof is immersed after development until the desired effect is +attained. Wash, etc. + +To clear the lines, or to make additions, or to write on the blue margin +of the proof a solution of potassium oxalate is employed. It dissolves the +blue without leaving scarcely any trace of it. The solution can be +prepared by mixing the two solutions whose formula is given below:(9) + +A. Oxalic acid 10 parts + Water 100 parts +B. Caustic potassa 121/2 parts + Water 100 parts + +The blue prints are permanent. When drying they darken a little from +oxidation; exposed to sunshine for some hours, they bleach considerably; +but in the shade the faded pictures progressively absorb oxygen from the +air and assume their original intensity and color in a period so much the +longer as the insulation has been more prolonged; it may take weeks if the +picture were much bleached. + + + + + +THE CYANOFER. (PELLET'S PROCESS.) + + +_This process gives blue impressions on a white ground from positive +cliches, and white impressions on a blue ground from negative cliches._ +It is termed "positive ferrotype process." + +The cyanofer is an application of one of the numerous and useful +inventions for which photography is indebted to A. Poitevin. In 1863 he +discovered that certain organic substances were rendered insoluble by +ferric chloride, and that they again became soluble; when under the +influence of light the ferric chloride has been reduced to a ferrous salt. +This curious phenomenon is the base of the process now to be described. +As usual the process has been modified by compounding the sensitive +solution in various ways and by minor details in the manner operating. +But although these modifications have rendered the process easier to work +with, there is not a great difference in the results obtained. We give +two formulas. Aside from the addition of gum arabic, which was suggested +by Mr. Pellet, and which constitutes the capital improvement of the +process, the formula is substantially that devised by Mr. Poitevin. + +Prepare three solutions as follows: + +A. Gum arabic, best 50 parts + quality + Water 170 parts +B. Tartaric acid 12 parts + Water 80 parts +C. Ferric chloride 35 parts in volume + solution at 45 + deg. Baume + +Mix gradually B to C, then C, by small quantities, in agitating briskly. +It is important to prepare the solution as directed, for by adding the +ferric chloride before tartaric acid, the gum arabic would be at once +coagulated. When the ferric chloride is mixed, the solution at first +thickens, but becomes sufficiently fluid for use in a certain period. It +does not keep, and should be employed the day it is made if possible. + +The paper, which should be well sized and calendered, and which, when not +giving good results by too much absorbing the sensitive solution, must be +starched as before directed, is coated either by brushing or by floating. +By the first method a roll of paper five yards long can be prepared +without great trouble, and give, perhaps, better results than if prepared +by floating; but the latter method is by far the the most convenient: one +does not generally prepare by brushing sheets of paper larger than about +30x40 inches. + +For brushing, the paper is pinned on a board, then, with a large badger +brush dipped in the sensitive solution, the latter is applied as evenly as +possible; after which, by lightly passing the brush over, the striae are +removed, the coating well equalized, and the paper hung up to dry. The +coating should not be very thin, and, above all, not too thick, for then +it would require an unusually long exposure to allow the light acting +through the whole thickness of the film, which is a sine qua non to obtain +a clear ground, i.e., not stained blue. + +To prepare by floating, pour the solution in a shallow tray, which needs +not to be more than 20x34 inches, 30 inches being the width of the drawing +paper usually employed; then roll the paper and place it on the solution. +Now, taking hold of it by two corners, draw it out slowly: the paper will +unroll by itself. This operation can be done by diffused daylight, but, +of course, the paper should be dried in a dark room. It dries rapidly. +Endless rolls are prepared by machinery. To expose, the drawing is placed +in the printing frame, face downwards, and the sensitive paper laid over +it. The whole is then pressed into contact by interposing a cushion +between the lid of the frame and the paper, and exposed so that the rays +of light fall _perpendicularly_ upon it. + +The cyanofer preparation is quite sensitive. From half a minute to two +minutes exposure, according to the intensity of the light and the +thickness of the coating, is sufficient in sunshine to reproduce a drawing +made on the ordinary tracing paper. In the shade, by a clear sky, the +exposure is about five times longer, and varies from half an hour to an +hour and more in cloudy weather, but then the design is seldom perfectly +sharp. + +The progresses of the impression is followed by opening one side of the +printing frame and examining the proof. The exposure is sufficient when +the paper is tinged brown on the parts corresponding to the ground of the +design. The image appears then negative, that is, yellowish on a tinged +ground. + +Another and more safe method of ascertaining the correct time of exposure, +which can be employed concurrently with the other, is to place a few +strips of the same sheet of sensitive paper between the margin of the +design, upon which a few lines have been traced, and the paper, and, +without opening the frame, to draw one of them, from time to time, and dip +it in the developing solution. If the whole strip be tinted blue, the +proof is not sufficiently exposed; but if the lines soon appear with an +intense coloration on the yellowish ground of the paper, and the latter do +not turn blue in a minute, at the most, the exposure is right. By excess, +the lines are with difficulty developed or broken. + +For developing, we provide with three wooden trays lined with lead or +gutta-percha, or, more economically, coated with yellow wax. The wax is +melted, then applied very hot, and, when it is solidified and quite cold, +the coating is equalized with a hot iron, whereby the cracks produced by +the contraction of the wax when cooling are filled up. + +One of these trays should contain a layer, about three-quarters of an inch +thick, of an almost saturated solution of potassium ferrocyanate (the +developer); the next be filled with water, and the third with water +acidified by sulphuric acid in the proportion of three per cent. in +volumes. + +All this being ready, the margin of the proof is turned upwards--so as to +form a disk of which the outside is the impressed surface--in order that +the ferrocyanate solution does not find its way on the back of the proof, +which would produce stains. Now the proof is laid, the lower edge first, +on the developer, and gradually lowered upon it, when, taking immediately +hold of it by the two corners nearest to the body, it is lifted out and +held upright to allow one following the development of the image; and, +presently, if any air-bubbles are seen on the proof, they should at once +be touched up with a brush wetted with the ferrocyanate solution; the +reason explains itself. + +The image appears at once. As soon as the fine lines are well defined, +the blue intense, and, especially, when the ground has a tendency to be +tinged blue, the proof is placed in the tray filled with water and in this +turned over two or three times, when it is immersed in the diluted +sulphuric acid. In this bath the print acquires a deep blue coloration, +consisting of Prussian blue, and the ground becomes tinted with a blue +precipitate without adherence, which is easily washed off by throwing the +liquid on the proof with a wooden spatula, or, better, by rubbing with a +rag tied to a stick. When the ground is cleared, and after three or four +minutes immersion to dissolve the iron salts acted on, the proof is rinsed +in water several times renewed to free it from acid, and hung to dry. + +There are two causes of failures in this process, viz., over and +under-exposure. In the former case the fine lines are broken or washed out +in clearing the proof (which may also arise from the drawing made with an +ink not opaque enough); in the latter the ground is more or less stained. + +The blue stains, the lines for corrections, etc., are erased with the the +potassic oxalate (_blue salving,_ as it is termed) whose formula has been +given. + +The additions, corrections and writing are made with a _Prussian blue ink_ +prepared by mixing the two following solutions: + +A. Ferric chloride, 4 parts + dry + Water 350 parts +B. Potassium 15 parts + ferrocyanate + Water 250 parts + +The precipitate being collected on a filter and washed until the water +commences to be tinged blue, is dissolved to the proper consistency in +about 400 parts of water. This ink does not corrode steel pens. + +It has been stated that the cyanofer process keeps for years if preserved +from the combined action of dampness and the air. The writer found in his +practice that the ferric salts in presence of the organic matters (the +sizes) acts as does potassium bichromate and renders, in a certain period, +the cyanofer film insoluble even after a prolonged insulation. Paper +freshly prepared is always more sensitive and gives better whites and +generally finer results.(10) + +The prints can be toned black in operating as in the cyonotype, but the +results are seldom good. + +Captain Pizzighelli's formula is as follows: Prepare + +A. Gum arabic 15 parts + Water 100 parts +B. Ammonia ferric 45 parts + citrate + Water 100 parts +C. Ferric chloride 45 parts + Water 100 parts + +For sensitizing mix _in order_: + +Solution A 100 parts +Solution B 40 parts +Solution C 20 parts + +The mixture very much thickens at first, but becomes sufficiently fluid +for use in a few hours. It keeps well for two or three days. Leaving out +B and replacing it by rain water, this makes also a good solution for the +cyanotype. + + + + + +THE BLACK OR INK PROCESS. (FERRO-TANNATE PROCESS.) + + +_This process gives black positive impressions on white ground from +positive cliches, and negative impressions from negative cliches._ It has +been attributed to Mr. Colas, but in reality it was invented by Mr. +Poitevin, who describes it as follows in his communication of May, 1860, +to the Societe Francaise de Photographie: + +"I make a solution containing--" + +Iron perchloride, cryst 10 parts +Tartaric acid 3 parts +Water 100 parts + +"I apply the paper on this mixture and let it dry spontaneously in the +dark, and at the moment of using it I completely desiccate it at a gentle +heat. Thus prepared the paper is of a deep yellow color. Light decolors +it rapidly, and ten or twelve minutes' exposure through a positive cliche +suffices to well impress it, that is, to reduce in the whites the iron +perchloride to the state of protochloride." + +"To print, one is guided by the decoloration of the paper, and even for +more facility I add to the solution of iron perchloride and tartaric acid +a small quantity of a solution of potassium sulphocyanide for the purpose +of obtaining a red tint, which is more visible and disappears also under +the influence of light in proportion to the decomposition of the +perchloride. One obtains then after exposure a red design on the white +ground of the paper. This red color is not permanent. It even disappears +by keeping the proof in the dark." + +"To develop and then to fix the design thus obtained I wash rapidly the +paper in ordinary water, or better, in water holding chalk in suspension. +The red coloration disappears, a part of the iron perchloride is washed +out, and in the parts which have not been acted on by light the +perchloride is transformed into sesquioxide. I replace then the water by +solution of gallic acid or of tannin and the image progressively appears +in ink-black. When I judge the image to be sufficiently intense I wash +the proof in rain water, in preference to ordinary water, which might +cause the gallic acid and tannin to turn brown. I sponge between sheets of +blotting paper and let the proof dry spontaneously." + +"If in place of gallic acid I use a diluted solution of potassium +ferricyanide (red prussiate of potash), Prussian blue is formed in the +parts acted on by light. The preparation is even sensitive enough to +permit one to obtain an impression in the camera obscura in developing by +the ferricyanide." + +"As to the proofs in gallate (or tannate) of iron, they can be transformed +into Prussian blue in a solution of potassium ferrocyanide (yellow +prussiate of potash) slightly acidified by sulphuric acid." + +The paper most suitable for this process is that which has been previously +well sized with starch, as explained in a special paragraph of this +pamphlet. Paper prepared with a film of coagulated albumen gives also good +results. It may be prepared by brushing as well as by floating, but in +either case the paper should be wetted on the surface only and dried +rapidly at a temperature of about 115 deg. Fahr. (46 deg. C.) and kept in +a dry place. It does not keep for more than from ten to fifteen days, +owing to the hygroscopicity of the iron compound. Mr. Colas, who prepares +the paper for the Parisian market, I think, states that he avoids its +deterioration by keeping it wrapped in blotting paper, between two sheets +of India rubber, to exclude air and dampness. Silvered albumen and plain +paper, well desiccated, could be kept in that way for a certain period, +especially if the blotting paper is impregnated with sodium bicarbonate +and well dried. + +Mr. A. Fisch advises to discard the preliminary washing and to develop +just on the removal of the proofs from the printing frame. In operating +in this manner the development is best made by floating, taking care that +the solution does not run off the back of the proof. + +The developer may consist of a dilute solution of nutgalls or of + +Tannin or gallic acid 4 parts +Oxalic acid 0.15 parts +Water 1,000 parts + +After developing the proof should be washed rapidly--under a jet of water, +if possible--for were the iron salt and the reagent not soon removed, or +any remain in the paper, the ground would be tinted violet. And whatever +be the care taken, it very seldom occurs that the whites are pure when the +proof is dry. This for half-tone pictures has not a great importance, but +for the reproductions of plans it is sometimes objectionable. In fact it +must be acknowledged that none of the processes now at our disposal--if we +except the so-called Artigues process described further on--gives an +entirely satisfactory result. A simple and expeditious process, yielding +intense black impressions on a white ground, is yet to be found for the +reproduction of plans, maps, etc., without resorting to a negative cliche +or drawing. + + + + + +THE CUPROTYPE. (BURNETT'S PROCESS.) + + +_This process gives positive impressions from negative cliches._ + +Uranic nitrate 10 parts +Cupric nitrate 2 parts +Water 100 parts + +Float for a minute strong, well-sized paper on this solution and let it +dry spontaneously in the dark. Expose until the image is visible, then +develop by floating on a solution of potassium ferricyanide at 5 per 100 +of water--the image appears at once with a rich brown color. When +developed, wash it in several changes of water until the unaltered salts +are eliminated. The proof is then fixed, and, if too intense, can be +reduced in water slightly acidified with hydrochloric acid. A fine black +image is obtained by toning in a solution of platinic chloride at 1 per +100 of water. + +The chemical actions giving rise to the formation of the metallic +ferrocyanide, of which the image consists, are quite complicated. Under +the luminous agency the uranic nitrate is first reduced, then the uranous +oxide acts on the cupric nitrate, forming cupric oxide, which is finally +reduced to the metallic state. This metal now converts the ferricyanate +in the ferro compound, which, by another action, forms both cupric and +uranic ferrocyanate. + +The following uranium process gives black impressions: + +In a saturated solution of tartaric acid dissolve freshly precipitated +ferric oxide, and keep the solution--ferric tartrate--in the dark. To +prepare the sensitizing solution, dissolve 20 parts of uranic nitrate and +from 1 to 3 parts of tartaric acid in 100 parts of water, and add a small +quantity of ferric tartrate, the proportion varying with the tint desired: +an excess gives a blue black. With this solution brush the paper over, +and, when dry, expose under the negative cliche, then develop with a +solution of potassium ferricyanate at 4 per 100 of water. To fix, it +suffices to wash in water, renewed three or four times. + +As pointed out by Mr. B. J. Burnett (see Introduction), many photographic +processes can be devised by basing them upon the various chemical changes, +of which uranous oxide, reduced by light from the uranic nitrate or +sulphate, is susceptible by means of metallic or organic reagents. + +In the Appendix some of the most important processes, with or without +silver salts as reagents, will be described. + + + + + +THE ANILINE PROCESS. + + +The aniline process was published in 1865, by Mr. Willis, the inventor of +the platinotype.(11) It is based on the oxidation of aniline by chromic +acid, thus: A sheet of paper brushed with a solution of potassium +bichromate and sulphuric acid, dried, and after insolation under a cliche +exposed to the fumes of aniline which, in reacting with the chromic +compound not reduced by light, forms a blue-black image. _The process +gives, consequently, a positive impression from a positive cliche._ + +There are various methods of operating; we will briefly describe them. + + SENSITISING SOLUTION. +1. Potassium 6 parts + bichromate + Sulphuric acid 6 parts + Magnesium chloride 10 parts + Water 150 parts + +Willis recommended 10 parts of solid phosphoric acid instead of sulphuric +acid; the latter forms a preparation about twice more rapidly reduced. + +2. Potassium 10 parts + bichromate + Manganous sulphate 4 parts + Potassium 20 parts + bisulphate + Water 300 parts +3. Ammonium 5 parts + bichromate + Ammonium chloride 5 parts + Cupric sulphate 1 part + Sulphuric acid 8 parts + Water 150 parts + +Good well-sized paper should be employed. Rives is too tender and absorbs +too much. Steinbach is better. For small sizes, whatever be the paper +selected, it is well to size it with starch and, if possible, to calender +it on a hot steel plate, or, in lieu, to iron it. This is not, however, a +sine qua non. The paper is sensitized by brushing or by floating. To +sensitize by floating, it should be left but for a few seconds on the +solution and removed by dragging it on a glass rod in order to remove the +superfluous liquid. Only the surface of the paper should be impregnated, +otherwise the whites would be more or less tinted and the image imbedded +not as sharp. + +Sensitized, the paper must be dried as rapidly as possible. It does not +keep, and should be employed the day it is prepared or the day after, +keeping it well wrapped in paper. + +As said above, it is exposed under a positive cliche, plans, designs, +etc., drawn on tracing paper or linen. The more transparent the material, +the more rapid the chemical changes. During the insolation--and it is very +short--the chromic compound is reduced, the parts corresponding to the +ground, that is, the transparent parts of the cliche, are discolored, +while those under the design remain unaltered; the image being, therefore, +faintly visible, and being formed of the chromic mixture, it is developed +by the fumes of aniline in a blue black tone. Therefore, if the paper be +not sufficiently exposed, the ground is colored like the image, although +not as deeply, since the dye formed is proportionate to the more or less +quantity of unreduced compound, and if exposed too long the image is +imperfectly developed or not at all by excess. + +The discoloration of the ground, which turns to a greenish hue, easily +indicates when the exposure is sufficient. But, to ascertain it, the +beginner should use _tests_ as in the cyanofer process. Mr. Endemann +regulates the time of exposure by partly covering a strip of the sensitive +paper with a piece of the tracing material upon which the design is made, +and exposing the whole until the covered part of the paper assumes the +same shade as the part directly exposed to light. + +To develop the print is placed in the bottom of a tray, which is then +covered with a lid upon which is pinned blotting paper well imbued with an +aniline and benzine mixture, or the reverse; that is, exposing the print +fastened to the lid and placing the aniline on the bottom of the tray. +The tray should be hermetically closed; that is a condition to obtain a +fine and equal coloration. For this purpose the lid should be well lined +with sheets of blotting paper and a weight placed over it during the +operation. Large prints are necessarily developed in a fumigating box +made ad hoc. The aniline solution consists of + +Aniline (commercial for 8 parts +red) +Benzine, rectified 100 parts + +In place of benzine, ether U.S.P., sp. grav. 0.837, may be used. + +When the proof is not over-exposed the development commences in a few +minutes. The image first takes a dirty black olive color which turns blue +in water, then the tone darkens to a dark-brownish tint. The time of +exposure to the aniline fumes depends on the time of insolation; if short, +the ground is soon tinted, and consequently the development should then be +stopped; if over-exposed, the development proceeds slowly. The darkest +tone is obtained by a rather full exposure which admits a long fumigation. +Sometimes the image takes a green color; it suffices then to wash the +proof in water rendered alkaline by a few drops of aqueous ammonia to +obtain the normal color. + +To somewhat improve the tone of the image and, if objectionable, to remove +the chromic oxide which tinges the ground greenish, the proof should be +immersed in a dilute solution of sulphuric acid 1:100, then washed twice, +and finally passed in ammoniacal water 1:100. + +Mr. Hermann Endemann has published, in 1866, the following process in the +_Journal of the American Chemical Society_, pp. 189 et seq.: + +The paper, which must be well sized with glue, 1:50, is sensitized with +the following solution and exposed when dry, but still slightly damp: + +A. Potassium 1 ounce or 480 + bicarbonate parts + Salt 1 ounce or 480 + parts + Sodium vanadate 2/3 grain or 0.66 + part + Water 20 ounces or 9,600 + parts +B. Sulphuric acid 2 ounces or 960 + parts + Water 10 ounces or 4,800 + parts + +When cold mix to A. + +"From the composition of the solution," says Mr. Endemann, "it is evident +that it must be strongly acid; but when this solution is exposed to light, +in the presence of the organic substances of the paper, the acidity of the +solution disappears, we obtain potassium and sodium sulphates, basic +chromium sulphate, salt and vanadic acid. While, therefore, the unchanged +parts of the paper remain acid, the changed parts acquire a neutral +reaction, and while the first will readily assimilate bases, the second +will not. Exposed in an atmosphere laden with water and aniline, the +aniline will be absorbed in those parts where the solution remains acid +and in proportion to the remaining acidity." + +To develop the image the paper is spread over the opening of a frame +tightly placed on a pan, in the bottom of which is heated a solution of +aniline in water, 1:50, until the image appears brown, and for further +development in a box laden with steam water, which, according to Mr. +Endemann, requires two hours to obtain a deep black coloration. To remove +the chromium compound the picture is immersed in a solution of aqueous +ammonia, 1:6, then washed and dried. + +A few years ago the aniline process was improved by developing the image +with the aniline-benzine mixture vaporized by steam in a box made +specially for that purpose, whereby a reproduction can be obtained in less +than ten minutes. + +In the photographic department of Messrs Poulson & Eger's Hecia +Architectural and Ornamental Iron Works, which is directed by Charles +Bilordeaux, this process is worked in the following manner: + +The developing is made of sheet iron with a door sliding up and down, it +being balanced by a counterpoise, and provided with a chimney. In the box +is a gutter, extending the whole length of the bottom, covered with muslin +and connected to a steam pipe; there is also a coil similarly connected. +After the insolation, which requires about one minute in sunshine, the +print is suspended in the box, the muslin brushed over with the solution +of aniline, and live steam allowed to pass through the gutter for only two +minutes, whereby the aniline being vaporized acts on the chromic salt and +develops the image; then the steam is allowed in the coil, and, in from +three to four minutes, the paper is dry and the picture finished. The +image stands on a slightly greenish ground, which is not objectionable for +the purpose the reproductions are made. + +The sensitizing solution is similar to that published by Mr. Endemann, +viz.: + +Potassium bichromate 460 grams +Sodium chloride 460 grams +Ammonium vanadate 0.75 gram +Sulphuric acid 1 liter +Water 13 liters + + + + + +THE PRIMULINE OR DIAZOTYPE PROCESS. + + +Primuline, discovered in 1887 by Mr. A. G. Green, an English chemist, is a +dye of a primrose color, possessing a great affinity for cotton fibers, to +which it is readily fixed by simply immersing the material for a few +moments in a hot solution of the dye. If the material so dyed be placed +in an acidified solution of nitrous oxide, the primuline is diazotized, +forming a derivative compound of a deeper color, which fades in the light, +and which in presence of amines and phenols gives rise to a variety of +dyes whose color depends on the reagent employed, while, when acted on by +light, the resulting compound is entirely deprived of this property. In +other words, the diazotized primuline acts as a mordant only when not +altered by the luminous action. + +The chemical change light effects in the diazotized primuline is not well +known. It is pretty certain, however, that nitrogen is set free, for if +gelatine imbued with primuline be immersed in water after insulation, +nitrogen is set free and can be collected as usual in a tub filled with +water and inverted on the substance. + +By itself diazotized primuline is slowly influenced by light, but quickly +acted on in presence of organic substances. It is more sensitive when +applied on cotton or paper than on wool, silk, linen, and such organic +compounds as gelatine, albumen, caseine, starch, etc. Its sensitiveness +is about one-tenth less with gelatine than with cotton. + +The sensitiveness of diazotized primuline to light, when united to organic +substances and the different colors which can be obtained with the +unaltered compound, have given rise to an interesting printing method, the +invention of Messrs. A. G. Green, C. F. Cross, and E. J. Bevan, which +yields _positive impressions from positive cliches_. The manipulations of +the process are simple: + +In a certain quantity of rain water, kept at nearly the boiling +temperature by an alcohol lamp placed under the vessel, dissolve per cent. +2 parts of commercial primuline, and in this immerse, by means of a glass +rod, some pieces of calico--free from dressing--turning them over several +times during the immersion. When the fibers are well imbued, which +requires from four to five minutes, remove the calico with the glass rod +and rinse it thoroughly in water. This done, wring out the superfluous +liquid as much as possible, and, finally, immerse each piece separately in +a solution of + +Sodium nitrite, 7 parts +commercial +Hydrochloric acid, 16 parts +commercial +Water 100 parts + +After turning the pieces of calico two or three times over, they are +rinsed to eliminate the acid, then drained and placed between sheets of +blotting paper to dry. All this, except the impregnation with primuline, +should be done in the dark room. + +As said above, primuline is transformed by nitrous oxide into a diazotized +compound, and consequently the material is now susceptible of being acted +on by light. It does not keep, and should be exposed, etc., soon after +its preparation. + +Paper is impregnated with primuline either by floating or brushing. The +best results are obtained with paper previously sized with arrowroot or +gelatine in order to keep the image entirely on the surface of the paper. + +Linen, silk and wool are treated as calico. + +The cliches should be positive to obtain positive expressions and somewhat +more opaque than those employed in the processes before described, else +vigor and intensity could not be obtained. Here we must state that the +primuline process seems to be better adapted for the reproductions of +drawings, such as made for the black process, and of opaque photo-cliches +in lines, or white and black, than for printing in half tone. + +When the material to print upon is thick and wholly impregnated with +diazotized primuline, it is advisable, since the insulation could not be +prolonged to effect the change through, to expose the back of the material +for a certain but short period in order to _clear_ it. This is especially +advantageous when the cliche is not of good intensity. + +During the exposure, which varies from 30 seconds to 10 minutes and more +by a dull light, the progresses of the luminous action is seen by the +bleaching of the material which assumes a dingy coloration. But in order +to ascertain when the decomposition is complete on the ground of the +image, it is well to use _tests_ as in the cyanofer process, dipping one +of them in the developer from time to time. + +The developers are compounded as follows: + + FOR RED. +Beta-naphthol 4 parts +Caustic potassa 6 parts +Water 500 parts + +Rub the alkali and the naphthol with a little water in a mortar and add +the remainder of the water. + + FOR ORANGE. +Resorcin 3 parts +Water 500 parts + +When dissolved add + +Caustic potassa 5 parts + + FOR YELLOW. +Carbolic acid, cryst 5 parts +Water 500 parts + + FOR PURPLE. +Naphthylamine 6 parts +Hydrochloric acid, in 6 parts +volume + +Mix in a mortar, then add + +Water 500 parts + + FOR BLACK. +Eikonogen, white crystals 6 parts +Water 500 parts + +Pulverize the eikonogen, add the water and, at the same time, the material +on its removal from the printing frame, and keep in motion until the +development is effected. + + FOR BROWN. +Pyrogallol 5 parts +Water 500 parts + +After the development, which requires but a few moments, it suffices to +wash the material to fix the image by eliminating the soluble compounds. +However, for purple the material should be passed in a dilute solution of +tartaric acid and not washed afterwards; it should remain acid. + +When it is desirable to obtain an impression in several colors, the +various developers are thickened with starch, then locally applied with a +brush on the image, which is always visible after exposure. + +For printing on wood, glass and porcelain, see further on. + + + + + + PRINTING ON WOOD, CANVAS, OPAL, AND TRANSPARENCIES + + +_Printing on Wood._--To print on a wood block a design to be engraved on +the same presents certain difficulties. In the first place, the +sensitizing solution must not be absorbed by the wood, but remain wholly +on its surface; then the photo film, although thick enough to produce an +image sufficiently intense to be distinctly visible in all its details, +should not scale or clip away under the graver, and not interfere in any +way with the work of the artist; the least touch of the graver must reach +the wood and make its impression. Lastly, the design should be permanent. +These difficulties will be avoided by adhering to the instructions given +in the lines following. + +The solution to render impervious the surface of the wood consists of + +Common gelatine 5 parts +Gum arabic 3 parts +Castile soap 3 parts +Water 100 parts + +Dissolve by heat on a water bath. + +To apply it, the wood is rubbed with fine sandpaper, then heated over a +spirit lamp to about 86 deg. Fahr. (30 deg. C.) and upon it is poured in +excess the liquefied and quite warm solution, which must be allowed to +penetrate in the pores of the wood by letting it gelatinize, when it is +wiped off clean. Nothing must remain on the surface of the wood. This +done, and while still damp, the preparation is rendered insoluble by +pouring over a solution of alum at 5 per 100 of water. The object of this +preliminary operation is to render the wood impervious, and therefore to +prevent the sensitizing solution to penetrate its texture. The wood is +then heated again and its surface whitened with a little silver white or +sulphate of barium, diffused in a small quantity of the following warm +solution: + +Gelatine 1 parts +Alum 0.1 part +Water 100 parts + +While wet, this is smoothed with a jeweler's brush, taking care to leave +on the wood, a very thin layer of the mixture, only sufficient to obtain a +white surface which, by contrasting with color of the wood assists the +engraver in his work. The wood should now be allowed to dry thoroughly, +when it is coated with a tepid solution of + +Isinglass 3 parts +Water 100 parts + +and dried. + +Now the sensitizing process differs according as whether the cliche is +positive or negative. In the former case the preparation is sensitized +with the solution employed in the black process, proceeding afterwards as +usual; in the latter, that is, when the cliche is negative, the best +process is the cuprotype.(12) + +For printing, special frames are employed to permit one to examine the +progress of the impression from time to time without the possibility of +either the wood block or the cliche moving. These frames open in two. +The upper frame is provided with screws on the four sides to hold firmly +the block when it is placed into contact with the cliche by means of the +screws fixed on the cross bars. As to the cliche, if it is made on a +glass plate, it is secured on the thick glass plate of the lower frame by +two wooden bars against it pushed by screws. + +When the block is ready for printing, the prepared side is usually +concave. It is straightened by slightly wetting the back and resting it +on one end, prepared side against the wall. + +_Printing on Canvas.--_The canvas should be first brushed with a solution +of aqueous ammonia in alcohol, 1:3, to remove greasiness until the thread +just commences to show, then, when rinsed and dry, rubbed with fine sand +to give a tooth, dusted, washed with a sponge and then coated with the +following solution, proceeding afterwards as in the cuprotype process: + +Isinglass 8 parts +Uranic nitrate 5 parts +Copper nitrate 2 parts +Water 200 parts + +_Printing on Opal, Celluloid, etc._, is quite simple; it suffices to coat +the material with the following gelatine solution, and, when the film is +dry, to proceed in operating by any one of the processes before described. + +The sensitizing compound may be incorporated to the gelatine solution, but +we prefer not to do it and to sensitize the plates as they are wanted for +use. + +A. Gelatine 4 parts + Water 70 parts in volume + +Dissolve and mix little by little in order: + +B. Chrome alum 0.25 parts + Water, hot 20 parts +C. Alcohol 10 parts + +When coated place the plates on a level stand until the gelatine is set, +and let them dry on a rack. + +_Transparencies._--Prepare the plate as directed above with + +A. Gelatine 6 parts + Water 70 parts +B. Chrome alum 0.3 part + Water, hot 20 parts +C. Alcohol 10 parts + +Sensitize with the uranic-copper solution employed in the cuprotype. By +this process transparencies of a rich brown, not actinic, color are +obtained. Consequently they can be used to reproduce negatives by the +same process. For lantern slides they may be toned black by platinic +chloride. + +To strip off the picture, apply, first, on the glass plate a substratum of +India rubber, 2 to 100 of benzole, coat with plain collodion, immerse the +plate in water as soon as the film is set, and when greasiness has +disappeared pour on the gelatine solution and proceed. + +For tranferring on any material, a sheet of paper is immersed in a +solution of India rubber cement in 20 parts of benzole, dried, coated with +the gelatine solution, sensitized, etc., by operating in the ordinary +manner. After development, the proof, being dry, is brushed over with +alumed gelatine moderately warm, dried, immersed in tepid water until the +gelatine is softened and tacky, when it is placed on the material and +squeezed into contact. This done, the transfer should be allowed to dry +thoroughly. Now, by imbuing the proof with benzole to dissolve the India +rubber, the paper is easily stripped off, leaving behind the picture +adhering to the material. + + + + + +TRACING PROCESS ON METAL. + + +We call the attention of metal engravers to this process. It is well +known that wood engravers have their original designs photographed on the +block in order to save considerable time by not making the drawing +themselves; moreover the cost is nominal, so to say, and the copy more +true and perfect than it can be done by hand. Why should not the copper +engraver and the aquafortist avail themselves of the same advantages? A +few do it secretly, no doubt, but the generality not knowing the process, +or, if so, not having tried it, think it is not possible or that it may +spoil their plates. This is an error. It can be done and very easily by +adhering to the following instructions: + +Dissolve 2 parts of ammonium bichromate in 100 parts of water, and in this +let soak for an hour or so 10 parts of Coignet's best gelatine, then +dissolve on a water bath, filter through flannel, and the solution is +ready for use. + +Before being coated, the plate should necessarily be cleaned free from +oxidation and greasy matters. This is done by immersing the plate for a +few moments in a warm solution of common potash, then rinsing and rubbing +it with chalk moistened with a little water, when after rinsing again and +draining the plate should be immediately prepared. + +To spread the gelatine solution in an even and thin layer, a tournette is +employed. The most simple consists of a round wooden stick of which the +upper part is carved in the form of a cup with an edge, or rim, about one +quarter of an inch broad. On this rim is melted some gutta-percha, upon +which the plate is pressed into contact and adhers quite firmly when the +gutta-percha is solidified. The stick is perforated at the lower end and +revolves on an iron pivot fixed at the bottom of the support, being held +in the opening on the platform of the same, as shown in the diagram on the +following page. + +The plate being fastened to the tournette, the warm gelatine solution is +flowed over it and spread to the edges by means of a glass rod or a piece +of cardboard, avoiding air bubbles. This done the tournette is set into +motion, and when the film is equalized, which is done in a moment, the +plate is detached, placed on a leveled stand and slowly dried with the +spirit lamp. + + [A Tournette] + +By a good light the exposure on the shade does not exceed twenty minutes +with a pretty intense transparency, and should be regulated with a +photometer. When the insulation is sufficient, the image is slightly +visible, and should be so. The plate is then bordered with banking wax +and bitten-in with a solution of ferric chloride at 45 deg. Baume, or-- + +Ferric chloride, crystal 20 parts +Hydrochloric acid 1 part +Water 100 parts + +The parts of the gelatine film the most acted on are impermeable, so to +say, and consequently do not allow the etching fluid to penetrate to the +copper; while those the least impressed are permeated according as to +their degree of insolation, Therefore, when the ferric chloride solution +is poured upon the film and carefelly brushed over with a soft brush, in a +few moments the image progressively appears, the deep blacks first, then +the half tints, and lastly the most delicate details, the whole requiring +but a few minutes. It is now that the etching action should be stopped by +washing under the tap. However, should by excess of exposure, or any +other cause, the details not appear within five or six minutes, the ferric +chloride should nevertheless be washed off, for then it may find its way +under the film and the plate would be spoiled. After washing the gelatine +is dissolved in a solution of potash, etc., when the image would be found +slightly engraved. + +Should the image be in half-tints, it would be advisable to apply a grain +of rosin on the gelatine film just before etching. To engrave on steel +the operations are the same, but on its removal from the printing frame +the plate should be soaked with water renewed several times until the +bichromate is washed off. The film is then dried spontaneously and +afterwards flowed for about two minutes with the Solution A, then, this +being thrown away, with the Solution B, which is allowed to act for a +similar period. + +A. Nitric acid, pure 120 parts + Silver nitrate 6 parts + Alcohol, 95 deg 50 parts + Water 75 parts +B. Nitric acid, pure 5 parts + Alcohol, 95 deg 40 parts + Water 60 parts + + + + + +GRAPHOTYPY. + + +This process consists in converting a cliche in half tones into one in +lines, which can be directly printed on paper, or impressed, by means of +an ink transfer made as explained before, on a stone, or on a zinc or +copper plate for etching in relief, or in intaglio, according as the +cliche is negative or positive. + +A cliche on gelatine, but preferably on a collodion film, is varnished +with a solution of yellow wax and bitumen in benzole and turpentine-oil: + +Bitumen of Judaea 8 parts +Yellow wax 2 parts +Benzole 40 parts +Turpentine oil 60 parts (filter) + +then etched as done to engrave in the aquafortis manner, the corrections +being made by applying with a brush some of the above varnish on the +defective parts, which are worked over when the varnish is dry. + +The tools are simply needles of various thickness ground in sharp square +and round points of different sizes. + +When the etching is finished, the parts which should form the ground, or +white parts of the design, being covered with the bitumen varnish is +non-actinic, or, in other words, does not admit the light acting on the +sensitive plate preparation employed to reproduce the design, except by an +exposure a good deal longer than that necessary to reduce the metallic +salts. + +The engraver will see at once that, although it greatly simplifies the +copying work and, consequently, saves much time, this process does not, +however, bind him to any rules and leaves him perfectly free to follow its +inspirations and make such alterations as he thinks proper to produce +artistic effects; in a word, the reproduction will no more be a picture +taken by a mechanical process, so to say, but an original drawing +reflecting his talent and characteristic manner. + +A similar process much employed by photo engravers, and presenting the +same advantages, is to convert an ordinary photograph on paper--or a blue +print, as devised by the writer--into a design in lines by drawing with +India ink, or the special ink of Higgins, and, this done, to wash off the +photographic image, the design being afterwards reproduced by the ordinary +processes as a negative or a positive cliche. + +When the photograph is a silver print especially made for the purpose in +question and, consequently not _toned,_ but simply fixed in a new +thiosulphate (hyposulphite) bath, and well washed--it is bleached by +flowing over a solution of-- + +Bichloride of mercury 5 parts +Alcohol 40 parts(13) +Water 100 parts + +If the photograph has been toned, i.e., colored by a deposit of gold, or +if it was fixed in a thiosulphate bath in which toned prints have been +fixed, then the image is dissolved by treatment in a solution of potassium +cyanide in alcoholized water. + +When a blue photograph is reduced, it is advisable before drawing upon it +to first reduce its intensity by a prolonged immersion into water. Pale +blue is a very actinic color which is not reproduced in photography, +except by the ortho-chromatic process, or if it does, the impression being +very weak, is not objectionable. When the image has not been sufficiently +or not at all bleached, the blue is dissolved by an alcoholized solution +of the blue solving. + + + + + +THE URANOTYPE. + + +This process, devised by J. Wothly, in 1864, did not receive from the +photographers the attention it merits, as it is always the case when a +process is patented, and can be replaced by another equally practical +which is not. It gives pictures of a very good tone, which are quite +permanent; we have some made in 1866, which are suffered no change +whatever, they seem to have been printed from yesterday. + +The first process given by Wothly does not appear to be complete. It has +been well described by H. Cooper and a gentleman who signs by the initial +letter X. + +The process published in 1865 by Wothly is as follows: A sheet of paper is +sized by brushing with a paste made of 24 parts of arrowroot in 500 parts +of water, to which are added a few drops of a solution of citric or +tartaric acid, then coated with a collodion consisting of 100 cubic +centimeters of plain collodion, a few drops of oil of turpentine and 30 +cubic centimeters of the following sensitizing solution: + +Nitrate of uranium 30 to 90 parts +Chloride of platinum 2 parts +Alcohol 180 parts + +The time of exposure is about that required for paper prepared with silver +chloride. The image is bluish-black but weak. After washing the print is +immersed in a solution containing 0.5 parts of chloride of gold for 2,000 +parts of distilled water, and then fixed in a bath of sulphocyanate of +potassium, which tones the image blue-black. + +It may happen that the proof is slightly tinted red. This arises from a +small quantity of lime in the paper which forms uranate of calcium. + +To prevent the proofs turning yellow, it should be washed in an +exceedingly weak solution of acetic acid. + +If, after exposure, the print is immersed, without it being washed, in the +gold bath, the image becomes rose-red, but the whites remain pure. The +effect is peculiar. + + + + + H. COOPER'S PROCESS (1865). + + + PREPARATION OF THE PAPER +St. Vincent arrowroot 200 grains +Boiling water 10 ounces + +Crush the arrowroot to fine powder, then rub it to a paste with a little +water, and let an assistant pour a few drams of boiling water while you +keep stirring all the time; finally, let him add the rest of the boiling +water, the operator still continuing the stirring. The paste is allowed +to cool, and will be thicker when cold than when hot. Remove the upper +portion entirely when quite cold, otherwise, if any left, it will give +rise to streaks. The author insists upon the necessity of all these +cares. Two sheets of paper are now placed side by side on a flat board, +then the surface of the first is covered with the paste by means of a +sponge, proceeding, before you leave it, all over the sheet in a +horizontal direction; the second sheet is covered in a like manner. By +the time the second sheet is pasted, the first one will be partially dry. +The sponge is now drawn over each sheet, in succession, in a perpendicular +direction in order to efface the streaks from the first sponging. If the +paste drags in a slimy manner, it is too strong, and a fresh arrowroot +must be prepared, because dilution only ends in failure. Why dry, the +paper is rolled under moderate pressure, and when it lies smoothly the +maximum pressure may be applied. + + PLAIN COLLODION. +Alcohol 12 ounces +Ether 4 ounces +Pyroxyline 80 grains + + SENSITIVE COLLODION. +Plain collodion 1 ounce +Nitrate of uranium, pure 30 grains +Nitrate or silver 5 grains + +Add the uranium first, and as soon as it has dissolved all that it can, +add a grain or two of soda, and when settled pour off the supernatant +collodion and add the silver.(14) To coat the paper with collodion, use a +board with a handle beneath, such as is used by plasterers. On this place +a sheet of paper, the edges being turned up about the sixteenth of an +inch; this enables the whole of the sheet to be covered without spilling +the collodion or allowing it to run on the back of the paper. + +There is a marked difference in the appearance of the prints when they +leave the pressure frame. Some samples of collodion cause the picture to +print of a beautiful green, others of a rich brown, and some of a yellow +or orange tint. The last take the longest of all to tone, and difficultly +assume the tint of well toned silver prints,(15) those printing to green +or brown tone very rapidly. + +After printing the pictures are placed in diluted sulphuric acid, 1 to 30 +of water, until the high lights are perfectly clear and white; this takes +from ten to fifteen minutes. After washing well under a stream of water, +they are placed in the toning and fixing bath. + + TONING AND FIXING BATH. +Sulphocyanide of ammonium 1 ounce +Water 12 ounces +Chloride of gold 1 to 3 grains + +After removing from this bath, the prints are immersed for a few moments +in water, and then rapidly washed. + + FORMULA FOR PREPARING THE PYROXYLINE +Nitric acid, sp. gr. 1.30 12 fluid ounces +Sulphuric acid, sp. gr. 36 fluid ounces +1.845 +Water 8 fluid ounces +Temperature 130 degrees Fahr. +Time of immersion 15 minutes. + + + + + X'S PROCESS (1865). (Secrets of the Uranotype) + + +_Preparation of the Uranium Compound.--_Precipitate the nitrate of uranium +from its solution by concentrated liquid ammonia. Let settle the +precipitate, decant, and wash in several changes of water. Dissolve it by +heat in pure nitric acid, _taking care not to add an excess of acid._ The +ammonio-nitrate of uranium salt is then crystallized and dried. Mix a +solution of 6 drams of this salt, dissolved in 3 drams of water, to a +solution of 15 grains of silver in 30 minims of water, and crystallize. +This salt is called _ammonio-nitrate of uranium and silver._ + + SENSITIZING SOLUTION. +Ammonio nitrate salt 3 drams +Alcohol 8 drams +Distilled water 15 drops +Nitric acid, pure 1 drop + +_Plain Collodion.--_Dissolve in a small quantity of ether 1 dram of Canada +balsam and 1 dram of castor oil, filter and let evaporate the solution to +the consistency of oil. + +Of this, add 10 minims to a collodion made of + +Alcohol 10 ounces +Ether 20 ounces +Pyroxyline 220 grains + + SENSITIVE COLLODION +Plain collodion 12 drams +Sensitizing solution 6 drams +Nitric acid 2 or more drops + +Keep this collodion in the dark, as it is quite sensitive. + + PREPARATION OF THE PAPER +Arrowroot, pulverized 1 ounce +Water 32 ounces +Solution of acetate of 10 drops +lead + +Heat to 100 deg. Fahr. and then add four ounces of albumen. The paper is +floated on this solution for five minutes and hung up to dry. The sizing +may also be applied with a sponge in the manner often described. + +The proofs should be slightly over-printed and, before toning and fixing, +placed for about ten minutes in the following solution: + +Distilled water 40 ounces +Acetic acid 1 ounce +Hydrochloric acid 1 ounce + +After washing in several changes of water, the proofs may be toned in any +toning bath, and then fixed with sulphocyanide of potassium, washing +afterwards in the usual manner. + + + + + +THE PLATINOTYPE. + + + + +This process, discovered by William Willis,(16) yields very fine +impressions which wholly consists of platinum and are, therefore, +chemically permanent. It has been described theoretically and practically +by Pizzighelli and Kuebl in a paper for which the Vienna Photographic +Society has awarded the Voightlander prize.(17) The following is an +abridgment of this important process, as described by the authors: + +The paper, calendered or not,(18) is sized with gelatine or arrowroot. +The color of the proof with the latter size is brownish black, and bluish +black with the former. + +To prepare the gelatine solution 10 parts of gelatine are soaked in 800 +parts of water and then dissolved at a temperature of 60 deg. C. (140 deg. +Fahr.), when 200 parts of alcohol and 3 parts of alum are added and the +solution filtered. + +To prepare the arrowroot solution 10 parts of the substance are powdered +in a mortar with a little water and mixed to 800 parts of boiling water, +added gradually in stirring. After boiling for a few minutes 200 parts of +alcohol are added and the mixture filtered. + +These solutions are employed warm. The paper is immersed for two or three +minutes and hung up to dry in a heated room, then immersed a second time +and dried by hanging it up in the opposite direction, in order to obtain +an even coating. + +The potassic platinic chloride is an article of commerce. It should be +soluble without residue in 6 parts of water and without acid reaction. In +this proportion it constitutes the normal stock solution employed in the +various formulas. + +The standard ferric oxalate solution is also found in commerce. Treated by +potassium ferricyanate it should not be colored blue, nor become turpid +when diluted with one-tenth part of water and boiled. The former reaction +indicates that it contains no ferrous salt, and the latter no basic +oxalate. + +The authors give the following instructions for preparing the ferric +oxalate solution, to which they attach much importance: + +Five hundred parts of ferric chloride are dissolved in 5,000 parts of +water and heated to boiling, when a solution of soda is added until the +liquid becomes alkaline.(19) About 250 parts of caustic soda are generally +employed for this purpose. The precipitate--ferric oxide--is now washed in +warm water until the last washing water is quite neutral to test paper, +then drained and mixed with 200 parts of pure crystallized oxalic acid. +The mixture is then allowed to stand in the dark for several days at a +temperature not exceeding 30 deg. C. (86 deg. Fahr.) At first the +solution from green turns to a yellow green, and finally becomes almost +brown. At this moment the excess of ferric oxide is filtered out and the +liquor submitted to a quantitative analysis, the result of which leads to +ascertain the quantity of ferric oxalate in 100 parts of the solution and +the excess of oxalic acid. The solution should then be diluted with +distilled water, such as it contains 20 parts of ferric oxalate per 100 +parts of water, and oxalic acid must be added in the proportion of from 6 +to 8 per 100 of the ferric oxalate, taking into account the quantity of +acid the solution already contains. The solution should be kept in the +dark. It is altered by light.(20) + + IRON CHLORATE SOLUTION +Ferric oxalate solution 100 parts +Potassium chlorate 0.4 parts + +This solution is employed to obtain more contrasts. + + PREPARATION OF THE SENSITIZING SOLUTION +Platinum solution 12 parts +Ferric oxalate solution 11 parts +Distilled water 2 parts + +This solution gives very soft tones with intense black. To obtain more +brilliancy we use the following proportions: + +Platinum solution 12 parts +Ferric oxalate solution 9 parts +Chlorate of iron solution 3 parts +Distilled water 2 parts + +To obtain results comparable to those which the silver printing out +process gives, the following mixture is employed: + +Platinum solution 12 parts +Ferric oxalate solution 8 parts +Chlorate of iron solution 4 parts +Distilled water 8 parts + +For very weak negatives, reproductions of drawings, etc., we use-- + +Platinum solution 12 parts +Chlorate of iron 11 parts +Distilled water 2 parts(21) + +To obtain proofs not completely black, as, for example, reproductions of +lead drawings, the solution may be diluted with half or the whole volume +of distilled water. But if the solution be applied on little absorbent +surfaces or on paper strongly sized it is not advisable to dilute it. + +_Preparation, of the Paper.--_The paper should be kept slightly moist in +order that it does not too completely absorb the sensitizing solution. +Therefore, when the atmosphere is very dry, it is well to keep the paper +in a damp place, in the cellar for example. Before sensitizing, which +should be done by a very diffused light, a quantity of the solution +proportionate to the surface to be sensitized (about 15 c.c., for a whole +sheet of Rives' or Saxe paper) must be measured, and spread with a large +brush(22) on the paper fixed with drawing pins on a board covered with a +sheet of blotting paper. When well impregnated, the paper is hung up to +dry in the dark room, and as soon as the apparent dampness of the surface +has disappeared, it should be dried immediately at a temperature of 30--40 +deg. C. (86--101 deg. Fahr). If the paper be dried too rapidly the +sensitive compound remains on its surface, and in developing the image +does not come out well. If, on the other hand, the drying is too slow, +the solution penetrates too much in the paper and the image is wanting of +vigor and does not appear very sharp. One cannot depart from this rule +that the desiccation from the moment the solution has been applied until +the paper is dry should last no more than from twelve to fifteen minutes. + +The sensitized paper is hygroscopic and must be preserved in a calcium +box. _It is a conditio sine qua non that the paper must be quite dry +before, during, and after printing, to obtain good results._ Dampness is +the greatest enemy in this process. + +For printing a pad of India rubber should be placed over the platinum +paper to prevent it from attracting the atmospheric moisture, and in damp +weather it is even advisable to cover it with several sheets of blotting +paper previously heated before the fire. + +The platinum paper is at least three times more sensitive than the silver +paper used in the printing-out process, under the reductive action of +light the yellow color of the prepared paper turns brown and then becomes +of a lighter color, nearly orange, so that the darker parts of the image +often appears more luminous than the dark half tints. No rule can be +given to regulate the insolation, but after a few trials it is easy to +judge when it is right by observing the progress of the reduction and the +color of the image. The orange color indicates the complete reduction of +the ferric oxalate. When the details in the lights are _faintly_ visible, +the exposure is generally right. + +The developer consists of an almost saturated solution of potassium +oxalate _acidified by oxalic acid,_ and for use heated to 80--85 deg. 0. +(176--184 deg. Fahr.),(23) in an agate glazed iron tray placed upon a water +bath at the above temperature. By simply drawing the proof over it, the +image is at once developed.(24) + +When the proof is thought to be over-exposed, the oxalate solution can be +employed at a lower temperature. If, on the contrary, it is +under-exposed, the solution may be heated even to the boiling point. + +The developer can be used over and over again. _It should always have an +acid reaction._ + +According to Mr. Borlinetto a sepia tone is obtained by using the +following cold developer: + +Saturated solution of 120 parts +potassium oxalate +Saturated solution of 13 parts +copper chloride +Oxalic acid 1.5 part + +After developing the proofs are _immediately_ immersed for fixing in a +solution of hydrochloric acid, 1 to 80 of water, renewed so long as the +paper is tinged yellow (about three times), leaving the proofs ten minutes +in each solution. Lastly, they are washed to remove the acid. + +The platinotype has been still improved by Captain Pizzighelli, who +devised the following methods of operating by which the impressions are +obtained by the continuous action of light, that is, without development, +thus rendering the platinotype just as simple as the ordinary printing-out +silver process. + +In these new processes to the sensitizing solution is added the alkaline +oxalate, which effects the reduction of the platinous salt during the +exposure to light. Consequently the prepared paper is insolated until the +image appears as it should be, or--which is exceedingly useful in cloudy +weather--until it is entirely visible but still deficient in delicate half +tones, for in the dark the action proceeds and the image developing itself +will be found finished in a period which may extend to a few hours. But +it can be, however, developed in a few seconds by immersion in a cold or +slightly warm solution of sodium carbonate, 1:25 of water. The image is +fixed as directed in the foregoing process. + +The paper, prepared exactly as in the former process and kept in the +calcium box until wanted for use, should not be employed quite dry, but +allowed to absorb a little moisture by hanging it in the dark room. +Hence, the India rubber and other protecting pads can be dispensed with. +They are even objectionable, for dampness is absolutely necessary to +promote the chemical changes by which the image is developed. + + A. AMMONIO-FERRIC OXALATE SOLUTION +Ferric oxalate solution 100 parts +Neutral ammonium oxalate 18 to 20 parts + + B. SODIO-FERRIC OXALATE SOLUTION +Ferric oxalate solution 100 parts +Neutral sodium oxalate 15 to 18 parts + +To prepare these two solutions the ammonium or sodium oxalate is dissolved +by small quantities at a time, and when the emerald color due to the +formation of the double oxalate commences to darken, the saturation being +then complete, no more of either salt should be added. The solution is +now well shaken with 3 parts of glycerine, allowed to settle and filtered. + +Any one of the double oxalates can be used. The ammonium tends to produce +softer pictures and bluish tones. To obtain more contrasts a little +potassium chlorate may be added. + + C. IRON CHLORATE SOLUTION +Solution B 100 parts +Potassium chlorate 0.4 part + + D. MERCURIC SOLUTION. +Mercuric chloride 20 parts +solution at 5:100 +Sodium oxalate solution 40 parts +at 3:100 +Glycerine 2 parts + + SENSITIZING SOLUTIONS. + FOR BLACK TONES. +Platinite solution, 1:6 5 parts +Solution B 6 parts +Solution C 2 parts + + FOR SEPIA TONES. +Platinite solution, 1:6 5 parts +Solution C 4 parts +Solution D 4 parts + +Intermediate tones are obtained by diminishing the dose of C and replacing +it by an equal volume of B. For this process the paper should be sized +with + +Arrowroot 2 parts +Sodium oxalate at 3:100 100 parts + +To dispense with this preliminary sizing Captain Pizzighelli adds gum +arabic to the platinite solution, whereby the sizing and sensitizing are +done in one operation. + +The gum arabic solutions are prepared as follows: + +E. Gum arabic in 40 parts + powder + Sodium ferric 40 parts + oxalate solution, + B + Sodium oxalate 100 parts + solution at 3:100 + Glycerine 3 parts + +Place the glycerine and the gum arabic in a mortar, then, stirring with +the pestle, dissolve by adding, little by little, the mixture, heated to +40--45 deg. C. (104--113 deg. Fahr.), of the solution of sodium ferric +oxalate and sodium oxalate. Let stand for about two hours and grind again +to dissolve entirely the gum arabic. Filter through muslin. + +F. Mercuric chloride 20 parts +solution, 5:100 +Sodium oxalate solution, 40 parts +3:100 +Gum arabic in powder 24 parts +Glycerine 2 parts + +Dissolve as said above. + + SENSITIZING SOLUTIONS. + FOR BLACK TONES. +Platinite solution, 1:6 5 parts +Solution E 6 parts +Solution C 2 parts + + FOR SEPIA TONES. +Platinite solution, 1:6 5 parts +Solution C 4 parts +Solution F 4 parts + +Mix just before use. The solutions do not keep. The paper prepared by +either one of these two processes can be exposed as in the _old_ process, +and the image developed bythe hot oxalate solution. + +The preparation of wood, canvas, etc., for the platinotype printing need +not to be described; it suggests itself. + + + + + CAUSES OF FAILURES. + + +_The images are veiled._ + +This defect may result from various causes, viz.: + + 1st. The stock ferric oxalate solution is impaired by a partial reduction + of the ferric salt into ferrous oxalate. The solution should be + preserved in an orange colored vial, and kept in the closet of the + dark room. It should be tested from time to time for the ferrous + salt with a solution of potassium ferricyanate. If it does not + contain any ferrous oxalate it can be used by adding to it a little + of the iron chlorate solution. + 2d. The paper has been exposed to light during the sensitizing or the + subsequent operations. One should bear in mind that the platinum + paper is twice more sensitive than silvered paper. + 3d. The sensitized paper has been dried at a temperature above 40 deg. + C. (104. deg. Fahr.) + 4th. Over-exposure. + +_The proofs are not sharp._ + + 1st. The sensitive paper has absorbed moisture. + 2d. It is too old. The paper cannot be kept good for over six weeks, + unless special care be taken. + +According to Mr. Bory, the sensitive paper altered by keeping is restored +to its original good quality by simply brushing it over with a solution of +0.05 parts of potassium chloride or the same quantity of potassium +chlorate in 100 parts of distilled water, or a mixture of these two +solutions, or one of iron chlorate. + +By treating the insolated paper with these solutions, the image is +destroyed, and the paper can be used again. One operates as for +sensitizing, taking care to desiccate the paper, as it has been directed. + +_The proofs are brilliant during the development, but become dull in +drying._ + +The paper not well sized. It has been dried too slowly. + +Remember that it should be quite desiccated within fifteen minutes. + +_The paper is more or less yellow._ + + 1st. The paper tinted with ultramarine. + 2d. The sensitizing solution or the developer are not sufficiently acid. + 3d. The washing (fixing) in the solution of hydrochloric acid was not + sufficient to eliminate the iron salts from the paper. + +_The proofs harsh, devoid of half tones._ + + 1st. The sensitizing solution contains too much iron chlorate. + 2d. Exposure too short. + +_The paper is stained._ + +The brush not kept clean while sensitizing. + +_Black spots._ + +They are generally due to metallic dust in the paste of the paper, or from +particles of undissolved salt in the platinite solution. + +NB: No good results can be expected unless the paper be kept absolutely +dry before, during and after exposure, when using the former (original) +process. + +Impaired sensitiveness of the paper, want of vigor, tinged whites, +muddiness, indicate dampness. + + + + +ARTIGUES' PROCESS + + +The Artigues process, so called, is, without any doubt, the best to be +employed for the reproduction of plans and drawings in lines. It is +simple, expeditious, and yields black impressions on a very pure white +ground which are absolutely permanent. And this is of the utmost +importance when the copies are to be used for military purpose, or kept in +archives, such as those of the Patent Office, for example. Should it not +require the use of negative cliches, it would certainly supersede any of +the processes previously described; moreover, as it will be seen, it can +be employed for many other purposes than that of obtaining duplicates from +original drawings. The objection is not even very great indeed, for the +design can be, without great trouble, transformed into a negative by the +aniline method described in the beginning of this work. + +The Artigues process is an adaptation for the purposes in question of the +carbon process invented by Poitevin. We shall describe it in extenso. + +The paper can be prepared with any one of the following solutions: + + 1st. Dissolve 21/2 parts of ammonium bichromate and 5 parts of best gum + arabic in 15 parts of water and neutralize with a few drops of + concentrated aqueous ammonia; then add 100 parts in volume of whites + of egg and a certain quantity of thick India ink, and, this done, + beat the whole to a thick froth. In ten or twelve hours the albumen + will be deposited and ready for use. + + The quantity of India ink added to the albumen should be such as the + paper be black when coated, but, however, sufficiently transparent + for one to see the shadow of objects placed on the back of it, and + the coating should not be thick. This is important in order to + allow the light acting through the whole thickness of the + preparation when the paper is insolated under the cliche, for, if + the film be too opaque or too thick (by addition of too much gum + arabic), it would be only impressed on its surface, and the image + dissolved during the development. The cause of this failure must be + explained. Under the action of light the bichromate employed to + sensitize the albumen is reduced into chromic oxide which render + insoluble this organic substance--or any other, such as caseine, + gelatine, gum arabic, etc.; therefore whenever the film is not acted + on in its whole thickness, the subjacent part being still soluble, + is necessary washed off and with it the superficial impressed part, + that is, the image. + + 2d. Take 10 parts of lamp black and work it up in a mortar to the + consistency of a thin paste by gradually pouring a little of a + solution of from 6 to 8 parts of gum arabic and 1 part of liquid + glucose in 100 parts of water, adding afterwards the remainder, into + which 21/2 parts of ammonium bichromate have been dissolved, and + filter through flannel. With this, coat the paper by brushing so as + to form a thin and uniform film, and pin it up to dry in the dark. + +These solutions keep well for a certain period. We have kept the albumen, +which we prefer to use, for two months in good condition; but the +sensitive paper does not for more than three or four days in taking the +usual care. It is more practical--and this is recommended--to leave out the +bichromate from the preparations, and to coat the paper, in quantity, +beforehand, and for use to sensitize it with a solution of potassium +bichromate at 31/2 per cent. of water applied on the verso with a Buckle +brush.(25) + +The bichromate solution should be allowed to imbue the paper for about one +minute, and having brushed it once more, the paper is pinned up to dry in +the dark room. It can also be sensitized from the back by floating, if +this manner is found more convenient. + +When dry the paper is impressed under a negative cliche of good intensity +until the design, well defined in all its details, is visible on the back +of the paper, which requires an insolation of about two minutes in clear +sunshine, and from eight to ten times longer in the shade. In cloudy +weather the exposure to light is necessarily very long. + +As explained before, the luminous action, by reducing the chromic salt in +presence of certain organic substances, causes the latter to become +insoluble; consequently if, on its removal from the printing frame, the +proof be soaked in cold water, for, say, ten minutes, and, placing it on a +glass plate or a smooth board, gently rubbed with a brush or a soft rag, +the parts of the albumen or gum arabic preparation not acted on will +dissolve, leaving behind the black image standing out on the white ground +of the paper. This done, and when the unreduced bichromate is washed out +in two changes of water, the operation is at an end. + +As to the theory of this and similar processes, the insolubilization of +the bichromate organic substance acted on by light was formerly attributed +to the oxidation of the substance by the oxygen evolved during the +reduction of the chromic salt into chromic oxide; but from the fact that +oxidation generally tends to destroy organic matters, or to increase their +solubility, it is more probable that it results from the formation of a +peculiar compound of the substance with chromic oxide (J. W. Swan); +moreover, gelatine imbued with an alkaline bichromate, then immersed first +in a solution of ferrous sulphate and afterwards in hot water, is +insolubilized with formation of chromium trioxide, Cr2O7K2+SO4Fe = +SO4K2+C2O4Fe+C2O3 (Monckhoven). A similar but inverse action occurs, as +shown by Poitevin, when gelatine rendered insoluble by ferric chloride +becomes soluble by the transformation, under the influence of light, of +the ferric salt into one at the minimum. + +The writer has improved the above process by simplifying the modus +operandi as follows: + +Instead of compounding the preparation with gum arabic and the coloring +matter, the albumen is simply clarified by beating the whites of eggs to a +froth, etc., and the paper is coated by floating for one minute, then hung +up to dry in a place free from dust. + +If the reader has any objection for albumenizing his own paper, he can use +the albumen paper found in the market for the printing-out silver process +generally employed by photographers. + +The paper is sensitized from the back with the potassium bichromate bath +by floating or by brushing. When dry, it is exposed as usual, but for a +shorter period than when the preparation contains the India ink or other +coloring matters which impede the action of light. + +The progress of the impression is followed by viewing, from time to time, +the albumenized side of the paper. When the design is visible, well +defined and brownish, the proof, being removed from the printing frame, is +rubbed with very finely powdered, or, better, levigated graphite, and, +this done, immersed in cold water for from fifteen to twenty minutes, when +by gently rubbing it under a jet of water with a soft rag, or with a +sponge imbued with water, the albumen is washed off from the parts not +acted on, leaving the design on a perfectly white ground. + +If instead of graphite, or any dry color insoluble in water, lithographic +ink, much thinned with turpentine oil, be applied on the print in a light +coating which permits one to see the design under it, and if, then, the +print be soaked in water and afterwards developed as just directed, an +image in greasy ink is obtained. And, furthermore, by replacing the +printing by transfer ink, one readily obtains a transfer ready for the +stone or a zinc plate to be etched in the ordinary manner. + +As usual there are two causes of failures in these processes, viz., under +and over-exposures. In the former case the image is partly washed off; in +the latter the ground cannot be cleared. The reasons are obvious. + +Mr. de Saint Florent gives the following processes:(26) A sheet of +albumenized or gelatinized paper is sensitized from the verso on a +solution of potassium bichromate, dried in the dark and exposed under a +positive cliche. After insolation, the proof is washed in water, to which +are added few drops of ammonia, then inked all over with an ink consisting +of 100 parts of liquid India ink, 7 parts of sulphuric acid and 3 parts of +caustic potassa, and dried in a horizontal position. When quite dry, the +proof is placed in water, and after an immersion of about ten minutes, +rubbed with a soft brush: the image little by little appears, and if the +time of exposure be right, it is soon entirely cleared, and, then, if not +enough vigorous, it may be inked again. The gloss of the image is removed +by means of a solution of caustic potassa at 10 per 100, and the proof +finally washed with care. + +If in lieu of albumen paper, one employs paper prepared with a thin +coating of gelatine, and dissolves the not acted on gelatine in warm +water, a very fine positive image is obtained by means of acidified inks +which will fix themselves on the bare paper. + +Positive impressions from positive cliches can also be obtained in +operating in the following manner: On its removal from the printing frame +the proof is washed, sponged between sheets of blotting paper, then +covered with not acidified India ink mixed with potassium bichromate, and, +when dry, exposed from the verso to the action of light. This done the +image is cleared with a somewhat hard brush. + + + + +THE CARBON PROCESS. + + +The carbon tissue is seldom prepared by photographers. However, for the +sake of completeness, we shall give the formula of the mixtures most +generally employed, and describe the manner of coating the paper on a +small scale. + +_Preparation of the Tissue.--_The gelatine generally recommended to +compound the mixture is the Nelson's autotype gelatine. Coignet's gold +label gelatine, mixed with a more soluble product, such as Cox's gelatine, +for example, gives also excellent results. + +Gelatine 110 parts +Sugar 25 parts +Soap, dry 12 parts +Water 350 parts + +The coloring substances consist of: + + FOR ENGRAVING BLACK. +Lamp-black 20 parts +Crimson lake 2 parts +Indigo 1 part + + FOR WARM BLACK. +Lamp-black 3 parts +Crimson lake 3 parts +Burnt amber 2 parts +Indigo 1 part + + FOR SEPIA +Lamp-black 2 parts +Sepia of Cologne 18 parts + + FOR PHOTOGRAPHIC RED BROWN. +India ink 3 parts +Crimson lake 4 parts +Van Dyck brown 4 parts + +For blue, Turnbull's blue is employed; for yellow, light chrome yellow; +for red, carmine dissolved in aqueous ammonia, evaporating, then adding +water, etc. (See further on.) + +To prepare the mixture, dissolve the sugar and soap in the cold water, add +the gelatine, let it soak for an hour, then dissolve it in a water bath +and mix by small quantity the colors finely ground together and wetted to +the consistency of a paste. After filtering through flannel the mixture +is ready for use. + +For coating, the method devised by Mr. Alf. Harman has been found +excellent in the hands of the writer, not only for the purpose in +question, but also for coating paper with gelatinous or viscous (gum +arabic) preparations. + +"Take two tin dishes, such as used for the development of the carbon +prints; arrange one on your bench tilted to an angle; the lower angle is +intended to receive the warm water for keeping the gelatine mixture to a +proper temperature. Into this angle of the tray arrange another tray +somewhat smaller, and keep it from touching the bottom of the outer one by +the insertion of any small article that will suggest itself. Into the +inner tray the gelatine mixture is to be poured." + +"The actual making of the tissue can now be proceeded with, and is so +simple and certain as not to be believed until put to the test. Purchase +a roll of paper-hanger's lining paper of good quality, cut it into widths +of about one and a half inch less than the width of your inner tray, and +in length of, say, thirty inches. For the success of the operation it is +necessary that the paper be rolled up the narrow way. Now having just +sufficient water at a temperature of 100 deg. Fahr. (38 deg. C.) into the +outer tray, pour the gelatine mixture into the inner one, and take one of +the lengths of rolled paper, and, holding it by both ends, gently lower it +on the surface of the gelatine; then at once slowly raise the end of the +paper, which will unroll itself and become beautifully coated in far less +time than it takes to describe. Twenty sheets may be coated in a quarter +of an hour, and be equal in all respects to that made by the most +expensive machine." + +In the description of this method of coating, Mr. Harman does not explain +how the gelatine should be allowed to set before hanging up the paper to +dry, which is, however, obviously important. It is as follows: Place on +the tray a smooth board a little larger than the sheet of paper, leaving a +small space at the end furthest from the body, and slowly, without a stop, +draw off the paper, prepared side uppermost, on the board upon which it +should remain until the gelatine is set. If the paper curls up, wet the +back a little with a sponge before coating. + +The following coating method, due to Mr. Chardon, is excellent for sheets +of paper of the ordinary photographic size, 18x22 inches. + +On a glass plate placed on a leveled stand, is laid a sheet of paper +previously wetted, which is then flattened into contact with an India +rubber squeegee, taking care to remove the air bubbles interposed. The +quantity of gelatine necessary to coat the paper is regulated by means of +a glass rod held by an iron lath, which serves to handle it; at each end +of the rod is inserted a piece of an India rubber tube whose thickness +regulates that of the gelatine layer. The mixture is poured from a small +teapot, at the opening of which has been adapted a bent glass tube about +three-sixteenths of an inch in diameter, between the rod and the lath, so +that by a simultaneous motion, one can equalize the gelatine as it is +poured on. When the gelatine is set the paper is hung up to dry. In +drying, the gelatine contracts, and, necessarily, causes a deformation of +the tissue, which curls up at the edges and loses its planimetry. To +prevent this, while the gelatine is almost dry, the tissue is placed under +pressure until quite desiccated. Dumoulin advises to apply on the film, +while still soft and tacky, a wooden frame, which, by adhering to it. +keeps the tissue perfectly plane as it dries. + + [Chardon's method of coating] + +_Sensitizing.--_The tissue is sensitized in a bath of potassium bichromate. +The degree of concentration of the bath, which varies from 2 to 5 per +cent. of water, is important. The tissue sensitized in a weak bath is +less rapidly acted on by light and yields more contrasts than when imbued +in a concentrated one. The former should consequently be employed for +printing weak negatives, and the latter for those which are intense. A +bath compounded with 30 parts of potassium bichromate, 1,000 parts of +water and 2 parts of aqueous ammonia, is used for printing negatives of +the ordinary intensity, the tissue being, then practically of the same +sensitiveness, a silvered paper insolated to obtain a print not +over-exposed. For intense negatives the ammonia should be discarded and +replaced by the same quantity of chromic acid. + +The time of immersion has also a certain influence on the results. The +less the tissue is allowed to absorb the solution the less sensitive it +is, but also the more the tendency of the half tints to be washed off +during the development. Generally the tissue should remain immersed until +it lies flat and the edges just commence to curl up, unless white and +black impressions are desired, but even then it is preferable to operate +as said above, using a bath at 2 per cent. + +For use the bichromate bath should be cooled down to 15 deg. C. (59 deg. +Fahr.), and much lower in summer, say 10 deg. C. (50 deg. Fahr.), and kept +at about this temperature by placing pieces of ice around the tray. At 20 +deg. C. (68 deg. Fahr.) the prints are more or less granulated; above this +the gelatine is softened and the reticulation greater; at 25 deg. C. (75 +deg. Fahr.) it may dissolve. + +The addition of alcohol to the bichromate bath--sometimes recommended to +harden the film and allow it to stand a higher temperature, and to hasten +the desiccation of the tissue--is objectionable, for the spirits tend to +reduce the bichromate, which is transformed into the green salt, and, +therefore, a partial or complete insolubilization of the gelatine is the +result. + +Aqueous ammonia added to the sensitizing solution has for its object to +permit one to keep the sensitive tissue for a somewhat longer period, but +it renders it less sensitive. If enough be added to turn the solution +yellow weak prints are obtained. + +The bichromate bath should be renewed often. It does not keep owing to the +presence of gelatine and other organic matters which it dissolves and +which cause the reduction of the chromic salt even in the dark. The +tissue prepared in such a bath is not very sensitive and the image +develops with difficulty, and even cannot be developed at all. + +As said above, the tissue is well sensitized when its edges commence to +curl up. It is then removed from the bath by drawing it on a glass rod +fixed at the end of the tray, and placed, prepared side down, on a +slightly waxed glass plate, rubbing it with an India rubber squeegee to +remove the superflous liquid, when it is hung up to dry. + +While wet the bichromated tissue is insensitive; the sensitizing can +therefore be made by daylight, but the drying should of course be done in +the dark room, that is in a room lighted by a candle or the sunlight +filtered through a deep orange window glass. + +_Caution.--_The soluble bichromates are very poisonous. By absorption they +produce skin diseases not without danger and very difficult to cure. Hence +when handling the wet tissue the fingers should be protected by India +rubber tips, and any yellow, stains on the hands should be rubbed with a +dilute solution of aqueous ammonia, and the hands well rinsed in water. + +_Drying.--_When the tissue dries rapidly it adheres well on the support +upon which it is applied for developing and yields brilliant images which +are easily cleared. On the other hand, were it allowed to dry slowly the +adherence would not be so complete, the image dull and developing with +difficulty. They may even refuse to develop at all from the +insolubilization of the gelatine. + +In winter and in the cool days of spring and autumn, the gelatine dries +quick enough in the air, but when the weather is warm and damp, the +gelatine, drying very slowly, may be so softened as to run off, or to +produce an entirely objectionable reticulation, or the defects above +mentioned. This may be avoided by drying it pinned up in a box, or a +closet, over quick-lime. + +When dry, the tissue is generally wrinkled, brittle, breaks easily in +handling and cannot be laid flat on the cliche; but by holding it over a +basin of boiling water, the steam in a few moments rendering it +sufficiently pliable to lay it flat between glass plates, where it should +be kept under pressure until wanted for use. + +The writer always dries the tissue in the following manner, which he +devised about sixteen years ago.(27) And not only the least trace of +reticulation is avoided, but the tissue, drying quite flat, lies in +perfect contact with the negative, which is quite important to obtain +proofs exactly sharp all over. + +A clean glass plate is rubbed with talc, or, which the writer prefers, +flowed with a solution of(28) +Yellow wax, pure 1 part +Benzine, pure 100 parts + +then strongly heated, allowed to cool and rubbed clean (apparently) with a +piece of flannel. After once more repeating this operation the plate is +coated with the following plain collodion:(29) + +Ether, conc. 250 parts, in volume +Alcohol, 95 deg 250 parts, in volume +Pyroxyline 3 parts + +When the film is set, the plate is immersed in filtered water until +greasiness has disappeared, when on its removal from the bichromate bath +the tissue is laid, without draining, upon it and pressed into contact +with the squeegee to remove the excess of liquid and, with it, the air +bubbles interposited. The tissue is then allowed to dry in the air on the +collodionized plate in the cold season, or, when the weather is warm and +damp, in a box in the bottom of which is placed a quantity of quicklime in +earthen dishes. When dry, the plates are placed one upon another, wrapped +in paper and kept in a dry place. When wanted for use the tissue is +stripped off and will be found quite flat with a beautiful surface to +print upon. + +One should avoid to keep the sensitized tissue in a moist and warm +atmosphere, for in less than ten hours it becomes insoluble even in +complete darkness. It should neither be kept in the air contaminated with +gaseous reductive matters, such as the products of the combustion of coal +gas and petroleum, sulphydric or sulphurous emanations from any source, +the fumes of turpentine oil, etc., which, by reducing the chromic salt, +cause the insolubilization of gelatine, prevent the print to adhere on the +support or the clearing of the image, which may even refuse to develop. + +The sensitive tissue keeps well for three or four weeks in cool and dry +weather, and no more than eight or ten days in summer unless well +desiccated and kept in a preservative box. If kept too long the image +cannot be developed. + +_The Photometer.--_The time of exposure is regulated by means of a +photometer. Of all the photometers which have been devised for that +purpose we do not know any one more practical than that suggested in 1876 +by Mr. J. Loeffler, of Staten Island. It is made as follows: On a strip of +a thin glass plate, 6x2 inches, make four or five negatives, 11/2x11/4 inch, +exposing each one exactly for the same period and developing in the usual +manner, but without any intensification whatever. It is even advisable to +reduce the intensity if they were opaque. Fix, etc., and apply a good +hard varnish. Now cover the back of these negatives with strips of +vegetable paper or transparent celluloid, or, better, of thin sheets of +mica, in such a manner as there be one thickness on the second negative, +two on the third, three on the fourth, etc., leaving the first one +uncovered. Then place on the whole a glass plate of the same size as the +first and border like a passe-partout. + +_The Negatives.--_For the carbon process the negatives should be intenser +than those intended for printing out on silver paper. However, good +proofs may be obtained from any negatives, so to say, by varying the +strength of the bichromate solution, as, also, by _using the tissue +freshly sensitized for weak negatives,_ in order to obtain vigor, and _for +strong negatives, the tissue two or three days after its preparation,_ +when it yields better half tones. Printing dodges are also resorted to. +That the most commonly employed consists to varnish the back of the +negatives with a matt varnish, or to stretch on the same a sheet of +mineral paper upon which the retouches are made by rubbing graphite, +chrome yellow, pink or blue colors to strengthen the shadows or the +whites, as the case requires. As a rule, it is advantageous to cover the +printing frame with tissue paper, whatever be the quality of the +negatives. + +The negatives should be bordered with deep yellow or orange-red paper to +form what is termed a "safe edge" upon which should rest the tissue in +order to prevent the margin from being insolubilized by the reductive +action of light. If this precaution were neglected it would be impossible +to strip off the paper without tearing the proof when the tissue is +applied on the support upon which the image is to be developed. + +Before exposing it is advisable to ascertain what the printing qualities +of the negative are by making on silvered paper a proof of it--_not +over-printed--_and another of the photometer, both being exposed at the +same time and for the same period. This done, compare the proof from the +negative cliche with those of the photometer, and mark the negative with +the number of that of the photometer to which it corresponds, stating the +shade of the proof next to it; for example: _No. 2_; _No. 3 faint, or +commences to appear,_ etc. This No. 2 and the observation will indicate +the intensity of the negative and serve as a guide for printing on the +tissue, since, as before explained, the silver paper is practically of the +same sensitiveness as the tissue prepared for negatives of the ordinary +intensity. + +_Exposure.--_To print, the tissue is laid over the negative, taking care +that it covers the safe edge, and a strip of silvered paper placed in the +photometer, then both the printing frame and the photometer are exposed to +light side by side. + +Unless the negative be weak, when more vigor is obtained by exposing in +sunshine, the printing should be done in the shade. It is a well-known +fact that the part of the bichromated film corresponding to the half +tones in the lights are not sufficiently impressed in comparison to the +blacks while impressed in direct sun's light in this as well as in the +collotype, photogravure and other processes with the chromic salts, +because the luminous action through the bare glass, or nearly so, which in +the negative represent the shadows and half blacks, is more energetic in +proportion than through the other parts, from which it results that these +parts being most acted on are made deeply insoluble through the thickness +of the film, and then require to be cleared by a treatment with water at a +higher temperature than the parts representing the half tints in the +lights of the picture, which are but superficially and slightly insoluble, +can stand. + +From time to time during the exposure the print in the photometer is +examined, and when a certain picture is printed to a certain shade, or +when the one next by commences to appear or is faintly printed, etc., the +exposure of the tissue is sufficient. This, as the reader has already +inferred, is a matter of experience, the guide being the knowledge of the +intensity negative tested as above explained. + +_Development.--_The carbon prints are developed either on a sheet of paper +upon which it should remain (single or simple transfer), or on a provisory +support to be afterwards transferred on paper or any other material +(double transfer). + +_Simple Transfer.--_This process is quite simple: The impressed tissue and +a sheet of paper coated with alumed (insoluble) gelatine are immersed face +to face in cold water, and when the tissue is softened both are removed, +one superposed on the other, and the whole, being placed on a glass plate +and covered with a thin oil cloth, is firmly pressed into contact with the +squeegee. The rationale of applying under water the tissue on the +gelatinized paper is to avoid the interposition of air bubbles. + +To operate by simple transfer the tissue should be impressed under a +reversed negative. The reason is obvious. + +_Double Transfer.--_By this method the carbon prints are generally +developed on porcelain or opal plates, which more easily than glass plates +permit one to follow the progress of the development and to retouch the +imperfections before transferring the picture on paper. + +In order that the image does not adhere on the provisory support a little +of the following mixture is spread over the plate, which is then pretty +strongly heated, and, when it has cooled down, polished lightly with a +piece of white flannel to obtain a very thin and even layer free from +striae. If the plate has not been used before for the purpose in question, +it should be waxed a second time in the same manner: + +Yellow wax 4 parts +Rosin 1 part +Turpentine or benzine 250 parts + +The plates can be developed on the plates so waxed, but for "full gloss," +that is, for enameled pictures, a film of collodion is applied on the +plates, which then, instead of being waxed, should to be simply flowed +with a solution of India rubber 1 to 100 of benzole: + +Ether 250 parts +Alcohol 250 parts +Castor oil 1 part +Pyroxyline 5 to 6 parts + +When the plate is coated and the collodion film set, it is immersed in +water until greasiness has disappeared and wanted for use. Then the +tissue, previously soaked in water, is applied upon it (taking care to +avoid air bubbles) and squeezed, lightly at first, with some force +afterwards, to insure a perfect contact. + +Zinc plates are also employed as provisory supports instead of glass, opal +or porcelain plates. The modus operandi is exactly the same.(30) The +plates should be well planed, free from scratches, etc., and well polished +to obtain glossy pictures without one having recourse to a film of +collodion. For matt pictures, i.e., without gloss whatever, the plate +should be finely granulated, and when waxing a very light pressure should +be exerted to remove the excess of wax, else it might be quite impossible +to strip off the picture in transferring on paper. + +For double transfer on biscuits, objects in alabaster, porcelain, wood, +any even or curved rigid materials, flexible supports are employed to +develop the pictures. These supports are prepared by fastening albumen +paper on a board and evenly brushing over the following hot compound, +filtered through flannel, which, when dry, is polished with a cloth: +Stearine 15 parts +Rosin 3 parts +Alcohol 100 parts + +The flexible supports should be waxed, then collodionized for full gloss, +as the glass, porcelain and metallic plates. + +Another method which the writer recommends is the following, due to Mr. +Swan: Immerse a sheet of paper in a solution of India rubber, 4:100 of +benzole, and let dry, which requires a few minutes. This is the flexible +support. Then after exposure, brush over the India rubber solution on the +carbon tissue, apply upon it the support when the benzole is evaporated, +and pass the whole under a rolling press to secure adhesion, then develop. +To transfer, soak the proof in tepid water, apply it on the material +prepared, as it will be explained further on, and when dry, imbue the +support from the back with benzole, to soften the India rubber, and strip. + +To dispense with a rolling press, the proof may be developed on lacquered +vegetable paper prepared by immersion in a solution of 10 parts of red +shellac in 100 parts of alcohol. After developing the proof is coated +with alumed gelatine, and when dry transferred as usual. To strip off it +suffices to imbue the paper with alcohol in order to dissolve the shellac. + +When the picture must be transferred on small spaces or on small objects +the most simple method--the most effective, perhaps--is the following, +devised some years ago by the writer and now employed for the ornaments of +"articles de Paris:" Prepare the provisory support as usual, but with a +thicker film of collodion; then, after developing and coloring, if +necessary, the picture is coated with gelatine, to which may be added some +zinc white or other colored substance to form a ground. This dry, strip +off, immerse the pellicle in water to soften the gelatine and transfer on +the material collodion side up. + +The proofs should be developed within three or four hours after +insolation, for the luminons action continues pretty actively in the dark, +and this for a long time; thus: a proof rightly exposed in the morning +behaves as one over-exposed if developed in the evening, and after a +certain period either can not be developed or refuses to adhere on the +support. However, the proofs can be kept for three weeks, may be more, +before development, if the soluble bichromate be washed off, the tissue +sponged and dried rapidly in the warm season. This capital improvement is +due to Mr. Charles Brasseur. + +It has been said that before being applied on the support the proof should +be immersed in water to soften the tissue. The time which it should be +allowed to absorb water has an importance which must not be neglected. If +it do not remain long enough to be soaked through, small invisible air +bubbles are formed on its surface, and interposing themselves between the +image and the support, form minute, brilliant, silver-like spots on the +finished picture; and, if the temperature of the water is above 20 deg. C. +(68 deg. Fahr.), the image will be more or less reticulated. The +temperature depends a good deal of the softness of the gelatine; 15 deg. +C. (59 deg. Fahr.) is safe, except, however, when the thermometer is in +the thirtieths (90th Fahr.), when the water should be cooled down a few +degrees lower, but not at the melting ice temperature, for then the proof +would not adhere well. As a rule, the tissue should remain in the cold +water until it becomes flat and shows a tendency to curl up. It is at +this very moment that it should be squeezed on the support. + +The proofs should not be developed immediately after transferring. The +adherence is greater and the pictures finer and devoid of defects when the +development is made half an hour, and even an hour, after. If developed +too soon the picture will be partly, and even entirely, washed off. +Hence, a number of transfers can be prepared beforehand, placing them, +face to face one upon another, in order that the tissue does not dry, +which is quite essential. + +To develop, the plate, with the tissue adhering to it, is placed in water +heated to 30 deg. C. (80 deg. Fahr.), where it is left rocking the tray +occasionally until the paper rises up by itself at the corners, when +taking hold of it by one corner, it is stripped off, leaving behind the +image buried in soluble gelatine. Should the paper offer any resistance +whatever, the gelatine should be allowed to become more soluble by +increasing the temperature of the water, or by a longer immersion. There +is, in fact, no objection to this. The plate--and that is a good +method--can be placed in an upright position in a tin box, made ad hoc, and +left therein in warm water until the paper detaches itself and the image +is partly developed _and the bichromate washed off._ This done, the plate +is held in an inclined position on a tray filled with water at 35 deg. C. +(95 deg. Fahr.), which is dashed with a wooden spoon on the image to clear +it from the non-acted-on gelatine. Presently one can judge whether the +exposure is right. If it is too short, the half tints in the shadows are +washed off, unless the negative be too intense, when a similar effect also +occurs in the whites. If it is too long, either the image is with +difficulty cleared or remains undeveloped. In the latter case, it is +recommended by some operators to increase the temperature of the +developing water to near the boiling point, and, for local clearing, to +pour it on. This we find objectionable, for the half tints are easily +washed off. A better process, when the picture can not be cleared by +water at 50 deg. (122 deg. Fahr.), or thereabout, is to use a solution of +common salt at 5 or 6 per cent. of slightly warm water.(31) It is even +preferable to finish the development in a tepid solution of potassium +sulpho-cyanide, 12:100. The dissolving action is long, but not only, as +said above, the half tints are best preserved, but blistering and local +washing-off are avoided. + +After development the plate is rinsed under the tap, then flowed two or +three times with a solution of chrome alum at 1 per cent. of water, then +washed, and finally allowed to dry spontaneously. + +It is objectionable to use a strong solution of alum, and in it to immerse +the plate for any length of time; the gelatine is considerably +hardened--which is not necessary--and more liable to crack by time in being +thoroughly desiccated. We discard the common alum which we found liable +to produce a slight reticulation. + +Two defects are complained of by the beginners, viz., the want of +adherence of the deep blacks, and, especially, the isolated and fine lines +when the picture is a reproduction of an engraving, a drawing, etc., and +the liability in half tone pictures of the delicate details being washed +out. The first defects are avoided by pouring a solution of boric acid on +the transitory support before applying the tissue and developing at a low +temperature with salted water. The second from an imperfect knowledge of +the properties of gelatine acted on by light in presence of a salt of +chromic acid. One should bear in mind that the degree of solubility of +gelatine so acted on, as also its degree of impermeability--which is +important in certain processes of photogravure--is proportionate to the +degree of insolation; thus, when not impressed, bichromated gelatine +dissolves in water heated to about from 25 to 30 deg. C. (77 to 80 deg. +Fahr.), and when acted on between 30 and 100 deg. C. (86 to 112 deg. +Fahr.), according as to the degree of insolation, that is, of reduction of +the chromic salt, the latter temperature being that of insolubility of the +parts the most acted on. The very delicate half tints do not, generally, +stand a temperature higher than 35 deg. C. (95 deg. Fahr.), and, +therefore, as the degree of insolubility of the various parts cannot be +ascertained, a priori, it is advisable during the development to increase +gradually the temperature of the water from this degree, and not to exceed +45 deg. C. (113 deg. Fahr.), in order to obtain the most perfect result +from a negative of good intensity. Indeed, by placing the supports on a +rack and immersing the whole in water heated to 30 to 35 deg. C. (86 to 95 +deg. Fahr.), the image will clear up by itself to perfection in a certain +period. This method is excellent for proofs in lines. Those from the +grained negatives employed in photogravure are still more perfectly +developed in a tepid solution of potassium sulphocyanate, since the +impressions wholly consist of insoluble parts (the lines) and gelatine not +acted on. + +_Retouching.--_The retouches are easily made. They should be done before +transferring when working by the double transfer process. + +The transparent spots, and any parts which should be altered, are +retouched with the material of the tissue dissolved in warm water; the +whites are cleared with a scraper; and any parts which are not intense +enough, or which should be blended by the addition of half tints, are +worked on the proof--to which a tooth has been given by rubbing with +cuttle-fish powder--by means of a stump and an appropriate color, a mixture +of lamp-black and carmine, for example, in very fine powder. + +The proofs can also be colored by chemical means (see further on), or with +water colors employed with a solution of chrome alum, 1 to 200 of water, +or gilt, silvered or bronzed with metallic powders applied with the +gilder's size thinned with turpentine on the proof previously coated with +a thin layer of alumed gelatine. + +_Second Transfer.--_To transfer, a sheet of enameled or simple transfer +paper is immersed in tepid water until the gelatine is softened and feels +slippery to the fingers. The support is then placed under water at +ordinary temperatures--not under 16 deg. C. (60 deg. F.)--for two three +minutes, then rubbed with a camel brush to remove the air bubbles, which +might be formed on the surface of the image, when, without draining, the +gelatinized paper is laid upon it, covered with the thin oil cloth, and +pressed into contact with the squeegee, commencing in the center to the +sweep off the water, then repeating the operation for the other half, as +explained to apply the tissue on the provisory support. When the whole is +quite dry, which requires three or four hours, the edges are cut with a +penknife and the whole stripped off. It may happen that the proof is +covered with minute, silver-like brilliant spots, which are nothing else +than very small air bubbles interposited between the carbon proof and the +transfer paper. They are caused by the gelatine paper not having been +sufficiently softened or not laid on the proof with proper care. The +defect may also arise from the transfer paper coated with not sufficiently +thick gelatine. + +To transfer on any rigid material, the proofs on flexible supports are +coated by floating on the following gelatine solution, then allowed to +dry, and, when wanted for use, immersed in tepid water to soften the +gelatine and secure adherence: + +Gelatine 50 parts +Water 400 parts +Solution of chrome alum, 6 parts +4:100 + +_Development on Absorbing Materials.--_The development of carbon prints on +absorbent material--such as canvas and palettes to be painted in oil, +etc.--cannot be made in the ordinary manner on account of the impossibility +to eliminate entirely the chromic salt which tinges the material yellow. +To turn the difficulty, it suffices to wash off in several changes of cold +water all the unaltered bichromate from the prints on their removal from +the printing frame, and to proceed as usual, or the prints can be allowed +to dry and transferred at some future time. + +Canvas should be prepared by brushing with a solution of aqueous ammonia +in alcohol, 5:20, to remove greasiness until the thread is apparent, and, +when dry, rubbed with sand to grain it--or to give a tooth, as it is +termed--then rubbed dry with a solution of soluble glass, 1 to 10 of +beer.(32) + +Palettes should be rendered impervious, or nearly so, by flowing upon them +a solution of alumed gelatine, which is allowed to penetrate into the +pores of the wood and the excess scraped off when solidified, when the +surface may be whitened, if necessary, as for printing on wood box, q.v. + +Opals, porcelain, or ivory should be prepared with the following +substratum: + +Gelatine 50 parts +Water 400 parts +Chrome alum, 4:100 6 parts + +Very fine carbon proofs having the appearance of pictures on opal plates +are made by transferring in the following manner, devised by the author: + +Develop on the ground surface of a glass or porcelain plate, well waxed, +to obtain a matt picture, or in the ordinary manner for "full gloss," and +when the image is retouched or colored, apply a thin coating of gelatine, +let dry and coat with the following opaque collodion: + +A. Ether, conc. 100 parts + Alcohol, 95 deg 90 parts + Pyroxyline 7 parts +B. White zinc in very 9 parts + fine powder + Castor oil 3 parts + Alcohol 10 parts + +Grind in a mortar, adding ultramarine blue and carmine, or a little of any +suitable coloring matters, and mix to A. When the collodion is dry, which +requires a few hours, strip the whole or back with strong white or colored +paper before stripping. A solution of gelatine with glycerine, white zinc, +etc., may be substituted for collodion when the pictures are employed as +ornaments on wood, etc. Carbon prints on celluloid are now made for +similar purposes. +OPAL GELATINE SOLUTION +Gelatine 150 parts +Glycerine 15 parts +Zinc, white 40 parts +Water 600 parts + +To which some coloring matters may be added according to taste. Grind the +white with the glycerine and a little water, mix to the gelatine dissolved +in the remainder of water, and filter through canvas. Apply the mixture +moderately hot, 30 deg. C. (86 deg. Fahr.) + +_Transparencies.--_The transparencies are printed on a special tissue sold +under the name of "diapositive." It differs from the ordinary tissue in +this, that the mixture contains a greater quantity of the color matter, +India ink, which is ground exceedingly fine. + +The proofs for transparencies should be printed deeper than those to be +seen by reflection, and developed on thin glass plates, free from any +defects, and coated with either one of the following substrata: + +Soluble glass 5 parts +White of eggs 15 parts +Water 20 parts + +The whole is beaten up to a thick froth and allowed to subside, when the +clear liquid is decanted, filtered through flannel and the glass plates +coated. The substratum should be allowed to dry for a few hours, and +rinsed under the tap before use. + +The other substratum consists of + +Gelatine 35 parts +Acetic acid, No. 8 250 parts +Alcohol, 95 deg 50 parts +Water 700 parts +Chrome alum, 4:100 60 parts + +Dissolve the gelatine in the acid at a moderate heat, add afterwards the +alcohol and water, and lastly mix the chrome alum by small quantities at a +time. + +These substrata are employed to avoid the peeling off of the image. To +prevent the entire desiccation of the gelatine, which is the cause of the +defect above alluded to, it is advisable to add glycerine to the washing +water after the image is cleared. Some operators recommend a coating of +flexible collodion, that is, prepared with castor oil, for the purpose in +question. We do not think that necessary when the transparencies are not +exposed to sunshine. If anything should be applied we would prefer the +encaustic. + +Carbon transparencies are invaluable for reproducing negatives in the +original size by the same (carbon) process, or for enlarging by the +collodion or gelatine process. For these purposes they should be made on +the special red tissue manufactured by the Autotype Company, of London, +Eng. They can, however, be made on the ordinary tissues. + +Whatever be the tissue employed, the transparencies for the reproduction +of negatives are seldom opaque enough, and should be intensified. This is +done by treating them with a very dilute solution of sodium permanganate, +which colors them olive green. + +Transparencies for lantern slides, etc., are best colored with the +couleurs a l'albumine of L. Encausse, sold by J. Reygondaud, Paris +(France). They are transparent.(33) + +_Toning and Intensifying.--_The carbon proofs can be toned and at the same +time intensified by reagents acting with chromic oxide. + +The dyes or coloring matters precipitated are not opaque, and, as a +consequence, not objectionable for transparencies. The following +processes are the most employed: + +Prepare three solutions as follows: + +A. Ferric sulphate 5 parts + Water 100 parts +B. Sodium carbonate 2 parts + Water 100 parts +C. Gallic acid 5 parts + Water 100 parts + +Dissolve the gallic acid in warm water. Filter each solution. They keep +well. + +To tone, the plate is immersed for, say, ten minutes in A, then, after +rinsing slightly, it is placed in B for the same period, rinsed again and +flowed with C until the desired color is obtained. The tone is a splendid +purple black color. If a solution of pyrogallol be substituted to that of +gallic acid, the tone is green, and to a green bordering to black when a +solution of catechu is used, the catechu exerting at the same time a +tanning action on the gelatine. After toning, the plate should be +thoroughly washed. + +A similar process consists to wet the plate under the tap, then to flow +over a mixture by about equal volumes of + +A. Ferrous sulphate 5 parts + Acetic acid, No. 8 5 parts + Water 100 parts, filter +B. Gallic acid 5 parts + Water 100 parts + +When toned, the plate is well washed, then flowed once with the alum +solution and again washed. The tone by this process easily turns to an +inky blue not very agreeable. The action should be stopped a little +before the desired color is obtained. + +It sometimes happens that the image in drying intensifies more then +necessary. It can be cleared with a solution of oxalic or citric acid. + +A brown sepia is obtained by toning first with potassium permanganate, 1 +per cent. of water, then, after washing, with a solution of pyrogallol. +If gallic acid be used instead of pyrogallol, the tone is black. By this +process a great intensity is obtained. A dilute solution of ammonium +sulphide can be employed as a clearing agent. + +Pyrogallol and silver nitrate give a warm black tone. + +Potassium bichromate followed by silver nitrate form a brick-red +precipitate of some opacity.(34) + +Chloride of nickel and potassium ferrocyanate produce a fine brown. + +Lime water and alizarine dissolved in alcohol dye violet. + +Alizarine and the caustic alkalies produce a variety of tints, from violet +to purple, according to the concentration of the solutions. + +Lead acetate and alizarine in ammoniacal solution dye purple. + +Potassium ferrocyanide and uranium nitrate produce a warm sepia tone. With +chloride of nickel the tone is brown. + +Ammoniacal solution of coralline diluted with water gives carmine red. + +Potassium bichromate and extract of indigo produce a fine greenish tone +suitable for landscapes. + +Extract of indigo colors blue(35) + +Some of these reactions can be applied to the printing processes with the +bichromates, etc. The paper should be coated with galatine. See the +Appendix. + +Other colorations can be obtained with dyes in utilizing (as shown by +Persoz) chromous chromic oxide as a mordant: alizarine, Brazil and yellow +wood (morus tinctoria), Fustet (rhus cotinus), etc. The extent of this +work does not admit of describing the numerous processes which can be +employed; they will suggest themselves to the chemist. + +The alkalies employed with the dyes should be employed in diluted +solutions, as being liable to produce reticulation. By applying the +coloring matters and the mordants thickened with a little starch, the +image can be colored with different colors. Lantern slides can be thus +colored with great ease. + + + +PREPARATION OF RED, YELLOW, OR BLUE TISSUES. + + +_Red Tissue.--_Dissolve 10 grams of carmine in 1 liter of aqueous ammonia +and evaporate. When the smell of the alkali has almost disappeared, add 1 +liter of rain water. Of this take 65 cubic centimeters, add 35 c.c.m. of +rain water, and in the solution let soak for an hour 15 grams of very +soluble gelatine, add 1 gram of sugar, and dissolve in a water bath. +Filter, and take of the mixture a sufficient quantity (25 c.c.m. for a +surface 18x24 centimeters) to cover a sheet of paper which has been +previously applied upon a glass plate in the following manner: In a tray +full of hot water, immerse the plate and the paper; remove the whole in +such a manner as the paper remains in contact with the plate; rub out the +excess of water with a squeegee, and flow the gelatine over the paper +still damp. Let cool on a leveled stand, and when the gelatine is +solidified to a consistent jelly, remove the paper from the plate and +place it to dry in an oven heated at not over 24 or 25 deg. C. + +It is desirable that in drying the paper does not curl up. To that end, +apply over it, before it being removed from the plate a wooden frame to +which the gelatine, still sticky, will sufficiently adhere to hold the +tissue when it stretches in drying. + +_Yellow Tissue.--_Pulverize to an impalpable powder 25 grams of light +chrome yellow in tablets (water color), and gradually add in stirring 1 +liter of rain water. Take 100 c.c.m. of this and into it let soak for an +hour 15 grams of the same gelatine used for the red tissue, add 1 gram of +sugar, then proceed as above. + +_Blue Tissue.--_In a liquid consisting of 85 c.c.m. of rain water and from +12 to 15 c.c.m. of blue ink, such as sold by stationers, let soak for an +hour 15 grams of the same gelatine and 1 gram of sugar, and proceed. + +_Preparation of Transfer Paper.--_Two kinds of transfer paper are +employed--the enamel and plain transfer paper. + +To enamel the paper: Dissolve 100 parts of barium nitrate in 500 parts of +water, and, on the other hand, 200 parts of sodium sulphate in the same +quantity of water. Mix, wash well the precipitate--barium sulphate--by +decantation, and when well drained, mix to the following solution: + +Gelatine, Coignet's 300 parts +Glycerine 80 parts +Ultramarine blue 1 part +Crimson lake 0.1 part +Water 2,500 parts + +Let soak the gelatine for, say, one hour, dissolve by heat, then add by +small quantities, stirring violently, 4 parts of chrome alum dissolved in +250 parts of hot water. Filter through flannel and coat the paper as +directed to prepare the tissue. The mixture should be employed +immediately after adding the chrome alum. + +The plain transfer paper is prepared in the same manner, leaving out the +barium sulphate and the coloring matters. + +_Preparation of the Silver Paper.--_Immerse the paper for two minutes in a +solution of-- + +Sodium chloride (common 2 parts +salt, dry) +Lemon juice 1 part +Water 100 parts (filter) + +When dry and wanted for use, sensitize the salted paper by floating for +one minute on-- + +Silver nitrate 8 parts +Nitric acid 0.1 part +Water 100 parts + +On its removal from the silver bath, sponge the paper between sheets of +blotting paper and hang it up to dry. + +ENCAUSTIC FOR SINGLE TRANSFER PROOFS. +White wax 25 parts +Mastic 3 parts +Turpentine 100 parts + +Dissolve by heat, first the mastic, then the wax, and keep for use in a +large mouthed vial. + + MATT VARNISH. +Sandarac 6 parts +Mastic 6 parts +Lavender oil. 0.5 parts +Ether 100 parts + +When dissolved, add 30 parts of benzine. The opacity of the film varies +with the quantity of benzine added; by excess the varnish dries +transparent. + + WATER COLORS WHICH RESIST THE ACTION OF LIGHT. +Red. Indian red. Light red. +Orange. Mars yellow. +Blue. Cobalt blue. French blue. Smalt. New blue. +Brown. Raw umber. Burnt + sienna. +Green Terre verte. +Yellow. Cadmium Yellow Roman ochre. + yellow. ochre. + + + + +APPENDIX. + + +Although we intended to only describe the printing processes without the +use of silver salts, we thought it would be well to complete this work by +giving the most practical and interesting processes ever published to +obtain permanent photographs; as they may give rise in the hand of +experimenters to useful applications. + +From time to time processes are published under "queer" names, which are +based on the well known actions of reagents on the ferric salts reduced by +light. They are derived from those described in the following pages. + +We call specially the attention of the reader to the process of Poitevin, +by which one can experiment with every ferric salts, citrate, lactate, +oxalate, tartrate, benzoate, etc., by simply exciting with the +corresponding acid. Observe that to obtain good results the paper should +be strongly sized; it is a sine qua non, although not recommended by +Poitevin. + + + +C.J. BURNETT'S PROCESS(1857). + + +"A capital process for many purposes," says Mr. Burnett, "is to float or +_steep_ the paper in a mixed solution of bichromate of potash and sulphate +of copper, as for Hunt's chromotype process.(36) I have mixed gelatine, or +occasionally grape sugar, or both with the solution;(37) but instead of +developing it with nitrate of silver, as in chromotype, wash out the salt +unaltered by light, and develop by floating on a solution of ferrocyanate +of potassium. The purple red color of the copper salt which now forms the +picture may be modified or changed in many ways,(38) viz., by soaking the +picture, after the ferrocyanate of potassium has been washed out of the +lights, in a solution of sulphate of iron. Solutions of gallic acid, +tannic acid with alkalies of carbonate, may also be employed to modify or +change the color. This process has the advantage that one may regulate +the exact tone (black or useful neutral tint) to the greatest nicety by +the time we allow the print to remain in the iron toning bath." + + + +GODEFROY'S PROCESS (1858). + + +Float the paper upon the following solution for three minutes and hang it +up to dry: + +Uranium nitrate 30 to 60 parts +Silver nitrate 8 parts +Water 100 parts + +(39) + +The sensitiveness increases in proportion to the quantity of uranium +nitrate. With the above formula the paper can be exposed in the camera, +or, for printing, under a negative cliche. + +In printing an exposure of five seconds in diffused light gives an image +perfectly visible, and a grayish black tone; ten seconds gives a vigorous +image almost of a black color; in from fifteen to twenty seconds the image +is very strong, with the color of an engraving. In sunshine the action is +necessarily much more rapid. + +The impression is developed by immersion in + +Ferrous sulphate 8 parts +Tartaric acid 4 parts +Sulphuric acid 1 part +Water 100 parts + +The image is rapidly developed. It is fixed by washing in water. + + + +DE LA BLANCHERE'S PROCESS (1858). + + +Uranium nitrate 25 parts +Distilled water 100 parts + +Filter the solution and keep it in the dark. + +The paper should be sized with a gelatine solution at 5 per 100 of water, +and, when dry, kept in the dark.(40) It is sensitized by floating five +minutes. + +The exposure under a negative varies from fifteen to twenty minutes in the +shade, and from one to three minutes, at the most, in sunshine. As a +rule, it is advisable to somewhat underexpose in order that the +development be regular, progressive, under control. + +The image is developed by floating, or immersion in + +Silver nitrate 2 parts +Distilled water 100 parts +Nitrate acid, C.P. a trace + +When the image is intense enough it is washed in several changes of water, +then toned in a solution of gold at 1 per 1,000 of water acidified with +traces of hydrochloride acid.(41) + +The following bath develops slowly, and gives very rich purple tones +without toning: + +Nitrate of silver 3 parts +Nitrate of uranium 1 part +Nitrate of cadmium 1 part +Alcohol 10 parts +Water 100 parts +Nitric acid traces + +_The developing solutions should be as little acid as possible, but not +neutral, for then the proofs would be veiled and grayish._ + +The image can also be developed in a solution of gold, or in a very weak +solution of mercuric chloride at 1 per 10,000. The proof must be +extremely well printed and left for from two to five minutes in the +mercuric solution. If the time of exposure is right, the image will +change but little in the solution, and will take, when treated with silver +nitrate, the most splendid tones. + +The proofs should be carefully washed when finished. If they were +developed with silver, they must be immersed in diluted aqueous ammonia, +which will perfectly clear the whites. If developed with chloride of +gold, the water should be heated to 60 to 80 deg. C. (140 to 176 deg. +Fahr.) + + + +HOUDOY'S PROCESS (1858.) + + +The paper is floated upon a lukewarm solution of gelatine at 5:100, and +when dry, on a bath of uranium at 10 or 15 per 100 of water. After +exposure to the sun the image is developed with a solution of silver +nitrate acidified with acetic acid. The exposure varies, according to the +nature of the negative, from one to ten minutes; it must be long enough +for the image being developed in from thirty to forty seconds. It is then +removed from the silver bath and placed in the following: + +Ferrous sulphate 3 to 8 parts +Acetic acid 2 parts +Water 100 parts + +In this bath the image takes a great vigor and appears entirely on the +surface of the paper. When the proof has been too long exposed it should +be washed slightly before placing it in the iron bath. Developed, the +image is, generally, of a sepia tone, which can be turned to black by a +solution of chloride of gold, 1:1,000, washing afterwards as usual. + + + +NIEPCE DE ST. VICTOR'S PROCESS (1859). + + +Red Prints. + + +Float the paper for fifteen or twenty seconds on a 20 per cent. solution +of nitrate of uranium and dry before the fire in the dark room. This +paper can be prepared many days before use. Expose in sunshine from eight +to ten minutes, according to the intensity of the light and the quality of +the negative, then wash in moderately warm water (50 to 60 deg. C.) for a +few seconds. This done, immerse in a solution of red prussiate of potash +at 2 per cent. of water; in a few moments the proof will become of a fine +blood-red color, like "sanguine." Wash, etc. + + +Green Prints. + + +Make a red print as above described, immerse it for a few minutes in a +solution of nitrate of cobalt and dry it without washing. Fix then in a +solution of sulphate of iron at 20 per cent. of water and 4 of sulphuric +acid. Wash and dry before the fire. + + +Violet Prints. + + +Prepare the paper in the uranium bath, expose, wash and develop in a +solution of chloride of gold, 1:200, until the proof has assumed a fine +violet color. Wash in several changes of water. + + +Blue Prints. + + +Sensitize the paper with a red prussiate of potash solution at 20 per 100. +Let dry, expose until the proof is slightly blue; immerse it for five or +ten seconds in a saturated solution of bichloride of mercury, wash only +once and immerse in a solution of oxalic acid--saturated when cold--heated +to about 55 deg. C. Wash in three or four waters and let dry +spontaneously. + + +Black Prints. + + +Float the paper on a mixture by equal volumes of a solution of iron +perchloride and another of uranium nitrate, each at 10 per 100 of water. +Expose and develop on a saturated solution of gallic acid. + + + + DR. T.L. PHIPSON'S PROCESS (1861). + + +Take a solution of perchloride of iron and, having precipitated the +peroxide with ammonia, collect the precipitate on a filter and wash it +with boiling water. Add the precipitate in excess to a warm solution of +oxalic acid. A beautiful emerald green solution is obtained, which must +be a little concentrated by evaporation and then set aside in a dark room +for use. The paper is floated for ten (?) minutes upon the green solution +of ferric oxalate, to which has been added a little oxalate of ammonia and +hung up to dry in the dark. + +Expose under a negative for from ten to twenty minutes, according to the +weather, and wash well the paper with rain water. Spring water will not +do on account of the lime it may contain, which will form oxalate of lime +in the paper (insoluble). When all the non-decomposed oxalate is washed +from the proof, a feeble image of oxalate of protoxide of iron, scarcely +visible, is left on the paper. To develop it and to obtain the vigor, the +tone and color of silver prints proceed as follows: + +Plunge the proof for a little while in a (weak) solution of permanganate +of potassium to which a few drops of ammonia have been added; in the bath +the image becomes brown and distinctly visible. It is then withdrawn and +immersed in a solution of pyrogallic acid for half an hour, after which it +is washed and dried. + +The image thus obtained can hardly be distinguished from silver prints; +the tone is soft, brilliant and permanent. + +This process is quite original and interesting. The theory is as follows: +Under the action of light the ferric oxalate is reduced in the ferrous +salt, insoluble, which, after the print has been cleared from the ferric +oxalate, is oxidized and reduced into ferric oxide by the alkalized +permanganate, the latter then forming colored compounds with reagents. + +It has been lately published in England under the name of "kallitype," a +new process--or old, ad libitum--which consists in developing the image in +ferrous oxalate by a peculiar silver compound whose formula is given +below. The paper is prepared by brushing with a strong solution of +neutral ferric oxalate dried rapidly--which is a sine qua non when using +deliquescent salts; and after exposure the image is developed, etc. + +Silver nitrate 50 grains +Sodium citrate 800 grains +Potassium bichromate 1 to 2 grains +Water 10 ounces + +"Dissolve the silver nitrate in 1 ounce of water, the citrate and +bichromate in the remainder and mix. The precipitate--silver citrate and +chromate--is then dissolved by adding 1 dram of ammonia .880, and after 35 +drops of strong nitric acid has been added the solution is ready for use." + +This process reminds us that of Robert Hunt (1842), and that of more +recent date (1863), of Borlinetto, who developed the image in black with a +silver nitrate alcoholic solution, 1:500, and after washing the picture in +a solution of citric acid, 1:10, fixed it by aqueous ammonia. But, +although that is not absolutely necessary, we would advise one working +this, or similar processes in which a silver salt is employed for +developing, to fix the image, after treatment with citric acid to clear +the proofs from iron salts, in a solution of ammonium sulphocyanate--which +has not the injurious effect of sodium thiosulphate (hyposulphite)--in +order to prevent the paper to be tinged by the reduction of the silver +nitrate which is mechanically retained in its fiber. + +The solution of ammonium sulphocyanate should be compounded with auric +chloride to tone the picture at the same time it is fixed; thus: + +Ammonium sulphocyanate 35 parts +Gold terchloride 0.15 part +Water 350 parts + +The solution can be used over again. + +In the processes devised by Dr. Phipson, Monckhoven and other authorities, +the double ammonio-ferric oxalate is rightly recommended instead of the +simple oxalate. Not only is the preparation more sensitive to the +luminous action, but better half tones are obtained. As usual, it is +advantageous to size the paper with starch. + +The ammonio-ferric oxalate is prepared by precipitating ferric chloride or +sulphate by aqueous ammonia, then washing the precipitate collected on a +filter until the washing water be neutral or does not evolve the smell of +ammonia. The precipitate is then placed in an evaporating dish, and by +small quantity is added a hot solution of ammonium oxalate until it is +nearly (not entirely) dissolved, when the solution is set aside for a few +hours, then filtered and evaporated to crystallization. For use, the +crystals of ammonio-ferric oxalate are dissolved in the proportion of 1 +for 5 of distilled water. The solution as well as the crystals should be +kept in the dark. + +If one object to the trouble of crystallizing, the solution can be +prepared by dissolving the ferric oxide in a hot solution of 30 parts of +ammonium oxalate and 25 parts of oxalic acid in 180 parts of water +observing that the oxide must be in excess.(42) + +The following sensitizing solution gives also excellent results: + +Ammonio-ferric oxalate 10 parts +Ammonio-ferric lactate 4 parts +Water 100 parts + +After exposure, which varies from five to ten minutes, according to the +intensity of the light and the printing quality of the negatives, the +picture appears negative from formation of ferrous oxalate. It may be +developed in a great many ways: by a solution of silver nitrate at 2 or 3 +per cent. of water acidified slightly by an organic acid--citric acid, for +example--or a diluted solution of ammonio-nitrate of silver, which most +likely constitutes the best developer; the image is black and consists of +metallic silver and ferric oxide, with formation of silver oxalate, which +dissolve in the ammonia. If the print be treated by a weak solution of +aqueous ammonia, the image turns green, then brown, and if, before the +latter coloration is obtained, gallic acid or pyrogallol be added, the +image becomes bluish-black or brown-black. In the same circumstances +tannin (gallo-tannin) produces a blue-black image; catechu-tannin(43) and +quino-tannin give green, etc. Employed as a developer, potassium +ferricyanate develops an image in prussian blue, and auric chloride one in +the characteristic violet metallic gold. To fix the images obtained by +the latter reactions, it suffices to wash them in a few changes of water, +and, if developed with silver, they can be toned by any of the alkaline +solutions of auric chloride used in the printing out silver process, etc. + +The photographs obtained by all these processes are permanent. + + + +DR. J.B. OBERNETTER'S PROCESS (1863). + + +Copper chloride 100 parts +Ferric chloride, sol. sp. 13 parts +gr. 1.5 +Hydrochloric acid, conc. 12 parts +C. P. +Water 1,000 parts + +Float the paper on this solution for about two minutes and hang it up to +dry. The keeping quality of the prepared paper is remarkable; it has been +kept for two years without apparent change; its sensitiveness is at least +one-third greater than that of silver albumen paper. Unless developed +within an hour or two, the vigor of the proof is much impaired; after +twenty-four hours a print can be taken over on the same. + +When exposed, only a faint image is visible. It should be fixed in the +following solution: + +Potassium sulphocyanate 12 parts +Sulphuric acid, conc. 1 part +Sensitizing solution 10 to 12 parts +Water 1,000 parts + +A print is floated on this solution, face downward, for three or four +minutes, taking care to agitate the liquid as little as possible; the +print is afterwards immersed and another one floated in its place, thus +proceeding until all the prints are immersed or the solution can hold no +more. A fresh solution is then added to strengthen it: the older the +solution the more rapidly and better it works. In this developer copper +cyanide is precipitated on the parts acted on by light, and this exactly +in the proportion to the luminous action. The time of immersion depends +on the method selected to finish the proofs; it its from five minutes to +half an hour. If the proof is immersed for, say, twenty-four hours, the +image comes out in a relief which may bring the shadows to two lines in +depth. When well developed and thoroughly washed, the proof can be dried +and the subsequent operations made at any convenient time. + +Various processes may be employed to give to these proofs the tone +required; thus: the prints well washed are placed in a solution of +ferricyanate of potassium at 6 to 12 per 100 of water, where they take a +red color increasing in intensity. If left over night the color becomes a +splendid velvet deep red with perfect clear whites. To obtain the color +of silver photographs one hour's immersion is sufficient. After this +operation the proofs are washed until the water is no more tinged yellow. + +By immersion in +Ferrous sulphate 100 parts +Iron sesquichloride 40 parts +Hydrochloric acid 80 parts +Water 200 to 300 parts + +the proofs undergo the following gradation of colors: red, reddish violet, +blue-violet, black and greenish black. As soon as the desired color is +obtained, the proofs are washed in acidified water and dried. + +The most beautiful purple violet is obtained by leaving the proofs in the +iron solution until green-black, and then washing for a moment in a dilute +solution of sub-acetate of lead. + +A brown-black may be produced by treatment, after washing, with an +ammoniacal solution of hypermanganate of potash. + +A weak solution of nitrate of silver also yields very fine pictures, but +the exposure should be very short, and the proofs must be fixed in water +containing a small quantity of oxalate of ammonia. + +In order to impart to the proofs the gloss of silver photographs, they +should be albumenized in the ordinary manner, and the albumen +insolubilized by well known means. + +The chemical actions in this process I explain in the following manner: On +the paper there are Fe2Cl3 and CuCl, the latter in excess. By the action +of light, and according to the transparency of the negative, Fe2Cl3 is +reduced to FeCl, while CuCl suffers no alteration. + +If the paper be immediately placed in an _absolutely_ dry room after +exposure, the picture remains unchanged. In a moist atmosphere FeCl +attracts moisture and, with a part of CuCl, is so decomposed that Fe2Cl3 +is formed together with Cu2Cl. + +After this action has commenced, if the proof be not immediately immersed +in a solution of sulphocyanate of potassium, Cu2Cl passes over to a higher +combination of chlorine, and the paper is again fit to be impressed anew +by the action of light. + +As long as FeCl or even Cu2Cl is present, if the print is immersed in the +sulphocyanate solution, sulphocyanate of copper is immediately formed on +the reduced parts, while on the others the sulphocyanide of copper, formed +and dissolved by the sulphocyanide of potassium in excess, becomes decom- +posed with water in soluble sulphocyanide of copper and deposited as such +on the parts already covered with the salt. + +Frequently the prints appear yellow from formation of the double +sulphocyanide of copper, but the color disappears by washing in water. +Red coloration is due to decomposition into ferrocyanide of copper. + + + +L. LIESEGANG'S PROCESS (1865). + + +Pour ammonia into a nitrate of uranium solution, wash the precipitate of +uranate of ammonia in distilled water, then dissolve in citric acid. + +Mix this solution of citrate of uranium and a little of a solution of +chloride of gold with a paste prepared by dissolving tapioca in hot water. +The quantity of chloride of gold must be small and the heat not too great, +otherwise the gold would be reduced. + +Spread the mixture with a sponge on the paper, which takes a brilliant +yellow color, and expose when quite dry; the proofs have the delicacy and +vigor of albumen prints. + +The proofs come from the frame with a bluish-black color; they should not +be toned, but merely fixed by washing until the yellow color of the paper +has disappeared. + +The color of the picture can be changed to a purple by a solution of +chloride of tin. + + + +GUARBASSI'S PROCESS (1867). + + +The paper is floated in the dark for four or five minutes on a saturated +solution of bichromate of potash. When dry, it is printed a little longer +than for silver prints and afterwards floated, face upwards, on a water +bath until all the unaltered bichromate is dissolved. It is then immersed +in the following solution, which improve by use and tones the pictures to +a reddish color: + +Saturated solution 4 parts +nitrate of mercury, as +free from acid as +possible +Saturated solution 1 part +bichromate of potash +Distilled water 28 parts + +This solution should be prepared, filtered and allowed to stand for some +time before use. The print is left in the bath until it has assumed an +intense red color, the whites remaining perfectly pure. It is then washed +and put in another bath to obtain a brownish tint. This bath is thus +composed: + +Conc. aqueous ammonia 2 parts +Distilled water 100 parts + +The print must be immersed at once, and when, in a short time, it has +assumed the proper color, it should be washed immediately. + +The picture is toned in a very diluted solution of chloride of gold, +1:7,000, in which the color passes from a light brown to a deep black or a +violet black tone, when it is washed in two changes of water. + + + +A. POITEVIN'S PROCESS (1870). + + +"I use a paper prepared with iron sesquioxide rendered sensitive to light +by tartaric or, better, citric acid in concentrated solution. This paper, +after desiccation and exposure to light, possesses the property of +reducing the solution of silver nitrate and that of chloride of gold, and +of turning blue with a solution of potassium ferncyanate in the parts +where light has reduced the iron sesquichloride into the oxide at the +minimum." + +"To coat the paper with an equal layer of iron sesqnioxide, I brush it +with a tuft of fine linen dipped in a solution of iron perchloride at 10 +or 12 per cent. of water, and dry the sheets in the dark. I immerse +afterwards these sheets, one after the other, in a tray containing aqueous +ammonia, in such a manner as to well wet each sheet successively. A +sufficient number of sheets being immersed, I pour off the ammonia in a +vial, and, in the tray, I wash them several times, and remove them one by +one to hang them up to dry, even in full light, the iron sesquioxide not +being sensitive to light." + +"The paper can be prepared in quantities beforehand. To use it I apply +upon each sheet a solution of citric acid at 30 or 35 per cent. of +water(44)--which may be done by daylight--and let them dry in the dark." + +"Exposed under a negative of the ordinary intensity, the paper is +impressed in sunshine in a few minutes; in the shade it requires about the +same time as chloride of silver paper." + +"After exposure the image is not visible, and without being obliged to +shelter it from light, I immerse the print in a solution containing about +1 per cent. of silver nitrate. This solution can be used over and over +again, by adding to it a little of the silver salt. It does not become +turpid by use; it simply turns slightly green from formation of iron +nitrate. The image appears soon and rapidly becomes vigorous; in half an +hour it will be completely developed. When the exposure is sufficient the +color is deep sepia, but not so intense if the quantity of citric acid is +feeble. No fixing is necessary; it suffices to wash in several changes of +waters." + +"The image can be toned with great facility by a weak solution of gold or +of platinum chloride, or, better, by a mixture of these two salts. If the +impressed paper be treated by a very diluted solution of potassium +ferrocyanate, one obtains very pretty blue proofs." + +"A weak solution of gold chloride develops a violet image. A solution of +platinum chloride has no effect." + +"All the various phases of this printing method can be followed in full +(diffused) light; there is only the desiccation of the paper when +sensitized with citric acid, which requires to be done in the dark." + + + + + + +***END OF THE PROJECT GUTENBERG EBOOK PHOTOGRAPHIC REPRODUCTION PROCESSES*** + + + +CREDITS + + +December 24, 2007 + + Project Gutenberg edition 10 + Martin Schub + + + +A WORD FROM PROJECT GUTENBERG + + +This file should be named 24016.txt or 24016.zip. + +This and all associated files of various formats will be found in: + + + http://www.gutenberg.org/dirs/2/4/0/1/24016/ + + +Updated editions will replace the previous one -- the old editions will be +renamed. + +Creating the works from public domain print editions means that no one +owns a United States copyright in these works, so the Foundation (and +you!) can copy and distribute it in the United States without permission +and without paying copyright royalties. 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