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diff --git a/17855.txt b/17855.txt new file mode 100644 index 0000000..edb7775 --- /dev/null +++ b/17855.txt @@ -0,0 +1,1582 @@ +The Project Gutenberg EBook of Hemp Hurds as Paper-Making Material, by +Lyster H. Dewey and Jason L. Merrill + +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 www.gutenberg.org + + +Title: Hemp Hurds as Paper-Making Material + United States Department of Agriculture, Bulletin No. 404 + +Author: Lyster H. Dewey and Jason L. Merrill + +Release Date: February 25, 2006 [EBook #17855] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK HEMP HURDS AS PAPER-MAKING *** + + + + +Produced by K.D. Thornton and the Online Distributed +Proofreading Team at http://www.pgdp.net + + + + + + + +UNITED STATES DEPARTMENT OF AGRICULTURE + +=BULLETIN No. 404= + +Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief + +[Illustration: USDA crests flanking bulletin banner] + +Washington, D.C. +PROFESSIONAL PAPER +October 14, 1916 + + +HEMP HURDS AS PAPER-MAKING MATERIAL. + +By LYSTER H. DEWEY, _Botanist in Charge of Fiber-Plant Investigations_, +and JASON L. MERRILL, _Paper-Plant Chemist, Paper-Plant Investigations_. + + + =CONTENTS.= + Page. +The production and handling of hemp hurds, + by Lyster H. Dewey: + + What hemp hurds are 1 + Pith, wood, and fiber 2 + Character of hurds affected by retting 2 + Proportion of hurds to fiber and yield per acre 3 + Hurds available from machine-broken hemp 3 + Present uses of hemp hurds 4 + Present supplies of hurds available 5 + Baling for shipment 5 + Cost of baling 5 + Summary 6 + + +The manufacture of paper from hemp hurds, + by Jason L. Merrill: + + Introduction 7 + Factors justifying an investigation of hemp hurds 8 + Character of the material 11 + Character of the tests 12 + Operations involved in a test 13 + Description of tests 16 + Comparison of the tests and commercial practice 21 + Physical tests of the papers produced 24 + Conclusions 25 + + +In preparing the report on the manufacture of paper from hemp hurds it +became evident that a short discussion of the agricultural aspects of +this material should be included in the publication. Such an article was +prepared, therefore, and the two reports are here presented together. + +[NOTE.--This bulletin should be useful to all persons who are interested +in the economic phases of paper making, especially to print and book +paper manufacturers. It also should be of interest to scientific +investigators and chemists.] + + + + +=THE PRODUCTION AND HANDLING OF HEMP HURDS.= + +By LYSTER H. DEWEY, _Botanist in Charge of Fiber-Plant Investigations_. + + +=WHAT HEMP HURDS ARE.= + +The woody inner portion of the hemp stalk, broken into pieces and +separated from the fiber in the processes of breaking and scutching, is +called hemp hurds. These hurds correspond to shives in flax, but are +much coarser and are usually softer in texture. + +The hemp stalk grown in a broadcast crop for fiber production is from +one-eighth to three-eighths of an inch in diameter and from 4 to 10 feet +tall. The stalk is hollow, with a cylindrical woody shell, thick near +the base, where the stalk is nearly solid, and thinner above, where the +hollow is relatively wider. + +In the process of breaking, the woody cylinder inside of the +fiber-bearing bark is broken into pieces one-half of an inch to 3 inches +long and usually split into numerous segments. The thicker lower +sections are split less than the thin-shelled upper ones, and they are +often left quite solid. + + +=PITH, WOOD, AND FIBER.= + +The inner surface of the hurds usually bears a layer of pith, consisting +of thin-walled cells nearly spherical or angular, but not elongated. +They are more or less crushed and torn. They are probably of little +value for paper, but they constitute less than 1 per cent of the weight +of the hurds. The principal weight and bulk consist of slender elongated +woody cells. The outer surface is covered with fine secondary fibers +composed of slender elongated cells, tougher than those of the wood but +finer and shorter than those of the hemp fiber of commerce. No method +has been devised thus far which completely separates from the hurds all +of the long fiber. From 5 to 15 per cent of the weight of the hurds +consists of hemp fiber, in strands from 3 inches to 8 feet in length. +Some fragments of the bark, made up of short cubical cells, usually dark +in color, cling to the strands of fiber. + + +=CHARACTER OF HURDS AFFECTED BY RETTING.= + +Nearly all of the hemp in the United States is dew retted. The stalks +are spread on the ground in swaths as grain is laid by the cradle. The +action of the weather, dew, and rain, aided by bacteria, dissolves and +washes out the green coloring matter (chlorophyll) and most of the gums, +leaving only the fibrous bark and the wood. The plants in this process +lose about 60 per cent of their green weight, or about 40 per cent of +their air-dry weight. + +The stalks are sometimes set up in shocks to cure before retting, and +after retting they are set up in shocks to dry. Each time the stalks are +handled they are chucked down on the ground to keep the butts even. In +these operations sand and clay are often driven up into the hollow at +the base of the stalks, and this dirt, which often clings tenaciously, +may constitute all objectionable feature in the use of hemp hurds for +paper stock. + +In Italy and in most localities in Russia and Austria-Hungary where hemp +is extensively cultivated, it is retted in water, but water retting has +never been practiced in the United States except to a limited extent +before the middle of the last century. Hurds from water-retted hemp are +cleaner and softer than those from dew-retted hemp. + +The fiber is sometimes broken from dry hemp stalks without retting. The +hurds thus produced contain a small percentage of soluble gums, chiefly +of the pectose series. Comparatively little hemp is prepared in this +manner in America. + +Process retting by means of weak solutions of chemicals or oils in hot +water is practiced to a limited extent. The hurds from these processes +may contain traces of the chemicals or oils and also soluble gums in +greater degree than those of the dew-retted or water-retted hemp. + + +=PROPORTION OF HURDS TO FIBER AND YIELD PER ACRE.= + +[Illustration: FIG. 1.--Hemp-breaking machine. The stalks are fed +sidewise in a continuous layer 2 to 3 inches thick, turning out about +4,000 pounds of clean fiber per day and five times as much hurds.] + +The yield of hemp fiber varies from 400 to 2,500 pounds per acre, +averaging 1,000 pounds under favorable conditions. The weight of hurds +is about five times that of the fiber, or somewhat greater from hemp +grown on peaty soils. A yield of 2-1/2 tons of hurds per acre may be taken +as a fair average. + + +=HURDS AVAILABLE FROM MACHINE-BROKEN HEMP.= + +Hemp hurds are available only from hemp which is broken by machines, +when the hurds may be collected in quantity in one place (figs. 1 and +2). Most of the hemp in Kentucky is still broken by hand brakes. These +small brakes are moved from shock to shock, so that the hurds are +scattered all over the field in small piles of less than 50 pounds each, +and it is the common practice to set fire to them as soon as the brake +is moved. It would be difficult to collect them at a cost which would +permit their use for paper stock. + +Where machine brakes are used, the hemp stalks are brought to the +machine as grain is brought to a thrashing machine, and the hurds +accumulate in large piles, being blown from the machine by wind +stackers. + +Machine brakes are used in Wisconsin, Indiana, Ohio, and California, but +to only a limited extent in Kentucky. Five different kinds of machine +brakes are now in actual use in this country, and still others are used +in Europe. All of the best hemp in Italy, commanding the highest market +price paid for any hemp, is broken by machines. The better machine +brakes now in use in this country prepare the fiber better and much more +rapidly than the hand brakes, and they will undoubtedly be used in all +localities where hemp raising is introduced as a new industry. They may +also be used in Kentucky when their cost is reduced to more reasonable +rates, so that they may compete with the hand brake. Hemp-breaking +machines are being improved and their use is increasing. The +hemp-growing industry can increase in this country only as machine +brakes are developed to prepare the fiber. A profitable use for the +hurds will add an incentive to the use of the machine brake. + + +[Illustration: FIG. 2.--Machine brake and hemp hurds. Hemp hurds from +machine brakes quickly accumulate in large piles.] + + +=PRESENT USES OF HEMP HURDS.= + +Hemp hurds are used to a limited extent for barnyard litter and stable +bedding, as a substitute for sawdust in packing ice, and, in rare +instances, for fuel. They are not regarded as having a commercial value +for any of these uses, though they are doubtless worth at least $1 per +ton on the farm when used for stable bedding. They are a waste product, +without value for other purposes which might compete with their use for +paper stock. + + +=PRESENT SUPPLIES OF HURDS AVAILABLE.= + +During the last season, 1915, about 1,500 acres of hemp have been +harvested outside of Kentucky and in regions where machine brakes are +used. Estimating the yield of hurds at 2-1/2 tons per acre, this should +give a total quantity of about 3,750 tons. Large quantities of hemp from +the crop of 1914, which are still unbroken in these areas, and large +piles of hurds undisturbed where the machines have been used during the +last two or three years, increase the total to more than 7,000 tons. +Hemp is now grown outside of Kentucky in the vicinity of McGuffey, east +of Lima, Ohio; around Nappanee, Elkhart County, and near Pierceton, in +Kosciusko County, Ind.; about Waupun and Brandon, Wis.; and at Rio Vista +and Stockton, Cal. + +In Kentucky, hemp is grown in most of the counties within a radius of 50 +miles of Lexington. No accurate statistics of the acreage are collected, +but the crop harvested in 1915 is estimated at 7,000 acres. A machine +brake will probably be used in Bourbon County and also in Clark County, +but most of the hemp in Kentucky will be broken on hand brakes. + + +=BALING FOR SHIPMENT.= + +The hurds will have to be baled to facilitate handling in transportation +and to economize storage space at the paper mills. The bales will need +to be covered with burlap or some material to keep them from shaking +out. They may be baled in the same presses that are used for baling hemp +fiber, but care must be exercised to avoid breaking the press, for the +hurds are more resistant than hemp fiber. A bale of hemp 2 by 3 by 4 +feet weighs about 500 pounds. A bale of hurds of the same size will +weigh about one-third less, or approximately six bales per ton. + +Rough hemp fiber as it is shipped from the farm is not covered; +therefore, the covering material must be purchased especially for the +hurds. A piece of burlap about 36 by 48 inches placed on either side of +the bale will be sufficient, but these pieces, weighing about 3 pounds +each, cost about 40 cents a pair. Baling rope, in addition to jute +covering, will cost at least 5 cents per bale, making the total cost of +covering and ties $2.70 or more per ton. Possibly chip-board, costing +about $33 per ton, or not more than 5 cents for the two pieces for each +bale, may be used in place of burlap. Chip-board, burlap, and also rope +ties may all be used for paper stock. Burlap covers might be returned, +to be used repeatedly until worn out, but chip-board could not be used +more than once. + + +=COST OF BALING.= + +If burlap covers are used the cost of baling, including covering, ties, +use of baling press, power, and labor will amount to at least 60 cents +per bale, or about $3.75 per ton. If chip-board can be used the cost may +be reduced to about $2 per ton. The cost of hauling and loading on the +cars will vary from $1 to $3 per ton, depending upon the distance and +the roads. The farmer must therefore receive from $4 to $6 per ton for +the hurds, baled, on board cars at his home station. + + +=SUMMARY.= + +Hemp hurds are the woody inner portion of the hemp stalk, broken into +pieces in removing the fiber. + +They are not used at present for any purpose that would compete with +their use for paper. + +Hurds are available only from machine-broken hemp, for the cost of +collecting them from the hand brakes would be too great. + +About 7,000 tons are now available in restricted localities in Ohio, +Indiana, Wisconsin, and California. + +The quantity is likely to increase as the use of machine brakes +increases. + +The hurds may be baled in hemp-fiber presses, with partial burlap covers +like those on cotton bales, or possibly chip-board covers. + +It is estimated that the farmers may deliver the bales on board cars +profitably at $4 to $6 per ton. + + + + + +THE MANUFACTURE OF PAPER FROM HEMP HURDS. + +By JASON L. MERRILL, _Paper-Plant Chemist, Paper-Plant Investigations_. + + +=INTRODUCTION.= + +The purpose of this paper is to report upon preliminary tests which were +conducted to determine the paper-making value of hemp hurds, a crop +waste of the hemp-fiber industry. + +The search for plant materials capable of being utilized in paper +manufacture is a comparatively recent but world-wide activity which has +for its object the husbanding of present sources of paper-stock supply +by the substitution of new materials for some of those which are rapidly +becoming less plentiful and more costly. + +The abstract idea of utilizing that which is at present a waste can play +no important role in such activities, the successful commercial outcome +of which must be based on the three fundamental factors--market or +demand for product, satisfactory raw material, and cost. + +Since hemp hurds are to be treated in this report as a raw material for +the manufacture of book and printing papers, the qualities, supply, +probable future, and cost of the material will be considered in +comparison with wood, with which it must compete. There seems to be +little doubt that the present wood supply can not withstand indefinitely +the demands placed upon it, and with increased scarcity economy in the +use of wood will become imperative. This effect is already apparent in +many wood-using industries, and although the paper industry consumes +only about 3 per cent of the total forest cut, it is probable that it +will be affected through this economy. Our forests are being cut three +times as fast as they grow, and as wood becomes more expensive proper +growing and reforesting will receive more attention. Thus, naturally, a +balance will be established between production and consumption, but as +this condition approaches its limiting values the price of wood may rise +to such levels that there will be a demand for other raw materials. + +The use of waste paper in conjunction with chemical wood pulp has +increased to enormous proportions, and it is probable that the increase +will continue. Although it is a cheaper raw material than wood, it is +reasonable to suppose that as the wood supply decreases and the price of +wood pulp advances, the price of waste paper will advance somewhat +proportionately. + +In view of these conditions it is advisable to investigate the +paper-making value of the more promising plant materials before a +critical situation arises. To be of substantial value the investigations +should include not only a determination of the quality and quantity of +pulp and paper which the material is capable of producing, but should +embrace a consideration of such relevant factors as agricultural +conditions, farm practice, assembling conditions, transportation, and +probable future supply. + +Certain cultivated plants seem particularly promising, because in the +harvesting of the regular crop that portion which might be utilized for +paper manufacture necessarily is either wholly or partially assembled. +To this class of plants belong corn, broom corn, sorghum, sugar cane, +bagasse, flax, hemp, and the cereal straws.[1] + +[Footnote 1: For descriptions of investigations of some of these crops, +see the list of publications at the end of this bulletin.] + +It is generally conceded that the employment of different raw materials +would probably yield products of a somewhat different quality than those +now prevailing in the markets, but the qualities of papers and the +public demands are so diversified and numerous that this possible +objection should not be serious. Ten years ago sulphite manufacturers +would not accept consignments of spruce logs if they contained over 5 +per cent of fir, while to-day many manufacturers tolerate 50 per cent. +Rope papers are found to contain not only jute, but when this raw +material is not plentiful, chemical pulp of various kinds. "Linen paper" +is often no more than a trade term. Not long ago printing papers were +made entirely from chemical wood pulp, but to-day if it is desired to +secure paper which is free from ground wood the specifications must so +stipulate. Writing papers, formerly made entirely from rags, now are +likely to contain either chemical or even ground-wood pulp unless the +specifications prohibit it. Without doubt, many paper manufacturers have +maintained certain papers up to a fixed standard for a long series of +years, but it is equally true that competition has lowered the standard +of a great many papers, some of which had acquired a distinctive +recognition. The employment of plant fibers will not necessarily lower +the present quality of papers, but if their employment does result in +products whose qualities are somewhat different from our so-called +standard papers it does not necessarily follow that such papers will not +find a ready market. + + +=FACTORS JUSTIFYING AN INVESTIGATION OF HEMP HURDS.= + +Hemp hurds form a crop waste, in that they necessarily are produced in +the raising and preparation of hemp fiber, and their present use and +value are comparatively insignificant. + +The assembling of the hurds may be effected with economy, since the area +in which hemp is handled with the use of machine brakes is restricted. +Although it must be stated that the present annual supply would not be +sufficient to justify the installation of a pulp mill nor would its +transportation to existing mills appear feasible, it is expected that +the available annual tonnage, especially in certain general sections, +will increase, due to the increased use of the machine brake. The +present tonnage per annum is approximately as follows: In the region of +Ohio and Indiana, 2,500 tons; in the Wisconsin section, 1,000 tons; in +the California region, 1,400 tons. + +In years of adverse weather conditions there are often large areas of +hemp which are not harvested on account of its poor quality; there are +also large areas of cut hemp which become overretted, due to inclement +weather. It has been suggested by some of the hemp raisers that this +large amount of material might be utilized as a paper stock. In these +cases the cost of the whole material would probably be somewhat higher +than that of the hurds, because either all or part of the cost of +harvesting and the total cost of breaking would have to be borne by the +paper maker. Moreover, the quality of this material would be so very +irregular and the supply so uncertain that it probably would not appeal +to the paper manufacturer. + +Without doubt, hemp will continue to be one of the staple agricultural +crops of the United States. The wholesale destruction of the supply by +fire, as frequently happens in the case of wood, is precluded by the +very nature of the hemp-raising industry. Since only one year's growth +can be harvested annually the supply is not endangered by the pernicious +practice of overcropping, which has contributed so much to the present +high and increasing cost of pulp wood. The permanency of the supply of +hemp hurds thus seems assured. + +The favorable location geographically of the hemp regions in relation to +the pulp and paper industry is a factor of considerable importance. The +Kentucky region is not at present in a position to supply hurds, as +machine methods have not been adopted there to any appreciable degree. +The Ohio and Indiana region, which at present has the greatest annual +tonnage, with the prospect of an increase, is situated south of the +Wisconsin and Michigan wood-pulp producing region and at a distance from +the eastern wood-pulp producing regions; therefore, it is in a favorable +position to compete in the large Ohio and Indiana markets. Since, as +will be shown, the hurd pulp acts far more like soda poplar stock than +sulphite stock, competition would be strongest from the eastern mills; +in fact, the hurd stock might very possibly meet with favor as a +book-stock furnish in the Michigan and Wisconsin paper mills, which are +within the sulphite fiber-producing region. Because of its very close +proximity to paper mills, this latter possibility applies with far +greater force to the Wisconsin hemp region, where a considerable +extension of the hemp industry is anticipated. + + +[Illustration: FIG. 3.--A representative sample of hemp hurds, natural +size, showing hemp fiber and pieces of wood tissue.] + + +=CHARACTER OF THE MATERIAL.= + +As received from Pierceton, Ind., the hurds consisted of a mixture of +tangled hemp bast fibers and pieces of broken wood of the hemp stalk. +(Fig. 3.) No reliable data were secured as to the proportion of bast +fiber in the total shipment of 4 tons, although two hand separations of +small representative samples gave results averaging 8 per cent. The +chemical character of the material was such and the quantity was so +small that any appreciable variation of the proportion should not affect +materially the treating processes finally adopted, yet its presence in +varying proportions undoubtedly would modify to some extent the quality +of the resulting paper product. Since the length of the ultimate bast +fiber averages about 22 mm. and the length of the ultimate hemp wood +fiber averages 0.7 mm., it is natural to assume that the bast fiber +would tend to increase the strength of paper produced from the hurds. +(Fig. 4.) + + +[Illustration: FIG. 4.--Fiber derived from the woody portion of the +hurds. x75. From a microphotograph.] + +The broken pieces of wood contained in the hurds varied in length from +mere particles which were somewhat finer than sawdust to pieces about +3-1/2 inches long, exceptional pieces being found which measured 6 +inches in length. The majority of the long pieces were between 2 and 3 +inches in length. In thickness the pieces ranged from one-eighth of an +inch, in case they were derived from the base of the hemp stalks, to +about one sixty-fourth of an inch in those pieces which were derived +from the top and branches of the stalks. In cross section the pieces +often were found to be a quarter or half of the rounded rectangular +woody shell of the stalk, although there appeared to be no regularity in +this respect. + +From the pulp-maker's standpoint the great irregularity in thickness, +length, and mass of the woody pieces militates decidedly against economy +in pulp production. The smaller pieces reduce by chemical treatment +sooner than the larger fragments and are thereby overtreated, which +results in a lower yield of cellulose fiber and a product composed of +undertreated and overtreated fibers, the production and use of which are +not satisfactory or economical. It probably would be found more +satisfactory, therefore, to screen or sort the hurds and treat the +various sizes separately and differently. + +Associated with the hurds was a small quantity of chaff and dirt, +composed chiefly of sand, soil, particles of hemp leaves and flowers, +and other extraneous matter. The sand and soil were present because of +the practice of placing the stalks in shocks in the field, the butts of +the stalks being in contact with the soil. It is a simple matter, +however, to remove the chaff and dirt by sieving, and this practice was +followed in most of the paper tests conducted with this material. + + +=CHARACTER OF THE TESTS.= + +Because of the similarity of hemp hurds to other materials which have +been tested by the Office of Paper-Plant Investigations, semicommercial +tests were conducted in cooperation with a paper manufacturer without +preliminary laboratory tests. Laboratory pulp and paper tests are +regarded only as a preliminary to semicommercial tests and therefore are +not employed unless the material in question presents new features which +should receive investigation before larger sized tests are undertaken. + +The advantages of cooperative mill tests are many, among which may be +mentioned the counsel and advice of the mill management and employees, +the services of specialized and skilled labor, facilities for comparing +the processes and the results of tests with commercial processes and +results, and the use of commercial or semicommercial types and sizes of +machinery. Tests conducted in this manner and on this scale are of a +different quality than is possible in those conducted in a laboratory, +and the results are susceptible of commercial interpretation with a fair +degree of reliability. It is found, in general, that the cost of +securing such equipment and service for a complete and comprehensive +test does not exceed $500, while the installation of an equally +satisfactory equipment alone would cost at least $50,000 and in many +cases very much more. Tests conducted in this manner constitute a direct +demonstration to the manufacturer, and the results obtained are found to +carry more weight when presented to other manufacturers for +consideration. + +It is well known that the method of conducting tests necessarily varies +with the size of the test. In the matter of yield determination, for +example, laboratory tests may be on such a small scale that the weighing +and sampling of the resulting cellulose fibers may be conducted by means +of chemical laboratory apparatus and analytical balance, while in tests +involving a matter of 5 to 10 pounds of material larger and different +types of equipment are necessary. When the tests are so increased in +size as to employ 300 or 400 pounds, still other types of equipment are +necessary for the treatment of the material and for a determination of +the yield of fiber. In tests involving tons of material the equipment +involves the use of machines. Accuracy in degree of control and in +results will vary materially with the size of the test. As the size of +the test increases, certain factors will vary in a beneficial manner, +while others will vary in a detrimental manner, so it is a question for +each investigator to decide, after taking all factors into +consideration, as to the size of test which will give the most +satisfactory results. In work of this nature it is found, on the whole, +that better results are obtained in large tests, although the control of +the factors and the determination of the yield of fiber are more +difficult than in smaller tests. + +In the tests described in this bulletin, the Department of Agriculture +employed a rotary digester of its own design,[2] comprising a shell 5 +feet 5 inches in length by 4 feet in diameter, capable of holding about +300 pounds of air-dry hurds. It is believed that a test of this size is +large enough to give satisfactory results and that the results are +susceptible of commercial interpretation, while at the same time they +are sufficiently small for complete control and to afford fiber-yield +figures which are both accurate and reliable. Two such rotary charges +gave enough fiber for one complete paper-making test. + +[Footnote 2: For a description of this rotary digester, see Brand, C. +J., and Merrill, J. L., Zacaton as a paper-making material, U. S. Dept. +Agr. Bul. 309, p. 28, 1915.] + + +=OPERATIONS INVOLVED IN A TEST.= + +A complete test on hurds comprises seven distinct operations, and the +method will be described, operation by operation, in the order in which +they were conducted. + +_Sieving._--The hurds for the first test were not sieved to remove sand +and dirt, but the resulting paper was so dirty that sieving was +practiced in all subsequent tests. The hurds were raked along a +horizontal galvanized-iron screen, 15 feet long and 3 feet wide, with +11-1/2 meshes per linear inch, the screen being agitated by hand from +below. Various amounts of dirt and chaff could be removed, depending on +the degree of action, but it was found that if much more than 3 per cent +of the material was removed it consisted chiefly of fine pieces of wood +with practically no additional sand or dirt; in most of the tests, +therefore, the material was screened so as to remove approximately 3 per +cent. It became apparent that a finer screen would probably serve as +well and effect a saving of small but good hurds. + +_Cooking._--Cooking is the technical term for the operation by which +fibrous raw materials are reduced to a residue of cellulose pulp by +means of chemical treatment. In these tests about 300 pounds of hurds +were charged into the rotary with the addition of a caustic-soda +solution, such as is regularly employed in pulp mills and which tested +an average of 109.5 grams of caustic soda per liter, or 0.916 pound per +gallon, and averaged 85 per cent causticity. Sufficient caustic solution +was added to furnish 25 or 30 per cent of actual caustic soda, +calculated on the bone-dry weight of hurds in the charge. After closing +the rotary head, it was started rotating at the rate of one-half +revolution per minute, and in about five minutes steam at 120 pounds per +square inch was admitted at such a rate that the charge was heated in +one hour to 170 deg. C., which is the theoretical equivalent of 100 pounds +of steam pressure per square inch. It was found, however, that when the +temperature reached 170 deg. C. the pressure was usually 115 or 120 pounds +instead of 100 pounds, due to air and gases inclosed in the rotary. At +this point the rotary was stopped and steam and air relieved until the +pressure dropped to 100 pounds, or a solid steam pressure. The +temperature was maintained at this point for the number of hours +required to reduce the hurds, which was found to be about five, after +which the rotary was stopped and steam relieved until the pressure was +reduced to zero, when the head was removed and the stock was emptied +into a tank underneath, measuring 5-1/2 by 6 by 2 feet deep, where it +was drained and washed. Samples of waste soda solution or "black +liquor," which were taken from some of the "cooks" for analysis, were +drawn while the stock was being thus emptied into the drainer. + +_Determination of yield._--For determining the yield of cellulose fiber +the stock in the drain tank was washed with water until free from waste +soda solution, when, by means of a vacuum pump communicating with the +space between the bottom and the false perforated bottom, the water was +sucked from the stock, leaving the fiber with a very uniform moisture +content throughout its entire mass and in a condition suitable for +removing, sampling, and weighing for a yield determination. Tests have +shown that it is possible to sample and calculate the yield of bone-dry +fiber within 0.05 per cent of the actual amount. + +It has been found that stocks from different materials vary greatly in +their ability to mat in the drain tank, thereby enabling a good vacuum +to be obtained, some stocks permitting a 25-inch vacuum to be obtained, +while others will not permit more than 5 inches. For this reason the +moisture content of the stock will vary from 65 to 85 per cent. + +_Washing and bleaching._--Washing and bleaching were performed for the +purpose of bleaching the brown-colored cooked stock to a white product, +since it was regarded as highly probable that the fiber would be +suitable for book-paper manufacture. The colored stock was charged into +a 400-pound beating and washing engine of regular construction and +washed about one hour, the cylinder washer being covered with 60-mesh +wire cloth in order to remove fine loose dirt and chemical residues. The +washer was then raised, the stock heated by steam to about 40 deg. C., and a +solution of commercial bleaching powder was added in the quantity judged +to be necessary, after which the stock was pumped to a large wooden +tank, to remain and bleach over night. If the stock was bleached +sufficiently white it was drained and washed from bleach residues, and +if not more bleach was added until a good color was obtained. The +bleaching powder used was estimated to contain 35 per cent of available +chlorin, as this is the commercial practice, and the amount required was +calculated to the bone-dry weight of the unbleached stock. More bleach +is required for undercooked stock than for stock which is properly +cooked or overcooked; therefore, the percentage of bleach required is an +indication of the quality of the cooked stock. Since bleaching is +usually more expensive than cooking, it is desirable to cook to such a +degree that the consumption of bleach will be held within certain +limits, depending on the raw materials used and the quality of paper to +be produced. In these tests it was desirable so to cook the hurds that +the consumption of bleach would not be over about 10 per cent of the +fiber. + +_Furnishing._--Furnishing is the operation of charging the beating +engine with the desired kind or kinds of fiber in the proper proportion +and amount and the adding of such loading and sizing agents as may be +necessary. As shown in the record of results, the furnish in these tests +consisted of hurd stock alone and of various proportions of hurds, +sulphite fiber, and soda fiber. The percentages to be given in the +record of the furnishes refer to the percentage of the total fiber +furnish, and this likewise applies to the loading and sizing agents. In +case sulphite or soda fiber was used, the commercial product in the dry +state was charged into the beating engine and disintegrated, after which +the hurd stock was added in the wet condition. + +_Beating._--Beating is that operation concerning which the paper makers +often say "there is where the paper is really made," and although the +statement may not be literally true it contains a great deal of truth. +It is the operation whereby the fibers are separated from each other, +reduced to the proper lengths, and put in such a physical or chemical +condition that they felt properly and form into a satisfactory sheet. It +is probable that the quality of the sheet depends more upon the proper +beater action than upon any other single operation. The action consists +in drawing a water suspension of the fiber between two sets of rather +blunt knives, one set being located in the bottom of a circulating +trough and the other set on the periphery of a roll revolving just above +the former set of knives. It is during this operation that the loading +and sizing agents are incorporated and the whole furnish is tinted +either to produce a satisfactory white or the desired color. + +The term "paper making," as used in this publication, means the +operation of forming the finished sheet of paper from stock which has +been furnished and prepared in the beater. In these tests a 30-inch +Fourdrinier machine of regular construction was used, a machine which +often is used for the production of paper for filling regular commercial +orders. The machine is designed to cause the water suspension of fibers +to flow on to a traveling wire cloth, whereby the water drains away. +More water is removed by passing the wet sheet through a series of press +rolls, after which the sheet is dried on steam-heated drums and passed +through polished iron rolls, which impart a finish to the sheet. A +Jordan refining machine was employed in conjunction with the machine to +improve further the quality of the fiber, and a pulp screen was used in +order to remove coarse and extraneous materials from the fiber. + + +=DESCRIPTION OF TESTS.= + +The nature of each complete paper test and the dependence of each +operation on the others were such that it does not seem advisable to +submit the results of the seven tests in tabular form. The numerous +cooks, however, which furnished the pulp for the paper tests are +presented in Table I in all essential detail. + + +TABLE I.--Data on cooking hemp hurds. + +------+-----------+------------+----------+--------------------+----------- + | | | | | + | | | | Cooking | Yield of + | Caustic |Strength of | | | bone-dry + | soda used |caustic soda|Causticity+--------+-----------+ fiber + Cook |(percentage| (grams per | of soda | | |(percentage + No. |of bone-dry| liter). | solution.| Time |Temperature|of bone-dry + | hurds). | | |(hours).| ( deg.C.) | unsieved + | | | | | | hurds). +------+-----------+------------+----------+--------+-----------+----------- +293 | 20.6| 100 | 75.3| 3| 166| +294 | 21 | 100 | 75.3| 3| 166| +295 | 21.6| 100 | 75.3| 3| 166| +296 | 20.3| 100 | 75.3| 3| 166| +301 | 21.9| 100 | 82.5| 4| 166| [3] +302 | 24.4| 100 | 82.5| 4| 166| +303 | 24.2| 100 | 84.3| 4| 166| 44.1 +304 | 25 | 100 | 84.3| 4| 170| 39.5 +305 | 25 | 100 | 84.3| 5| 170| 39.4 +306 | 27.8| 107.5| 84.3| 4| 166| 36.5 +307 | 26.7| 107 | 84.4| 5| 170| 38.1 +308 | 26 | 107 | 84.4| 5| 170|\_ 37.3 +309 | 27.3| 107 | 84.4| 5| 170|/ +310 | 27.1| 107 | 84.4| 6| 170| 37.0 +311 | 27.2| 107 | 84.4| 6| 170| 36.8 +312 | 28.3| 116.5| 85.5| 5| 170| 35.9 +313 | 29.1| 113.1| 84.9| 5| 170|\_ 35.2 +314 | 29.1| 109 | 83.9| 5| 170|/ +315 | 29.4| 109 | 83.9| 5| 170| 34.9 +316 | 30 | 109.5| 84.9| 5| 170| 37.2 +317 | 29.6| 109.5| 84.9| 5| 170| 37.0 +318 | 29.6| 107 | 84.8| 5| 170| 37.7 +319 | 29.4| 107.5| 84.2| 5| 170|\_ 35.4 +320 | 29.3| 107.5| 84.2| 5| 170|/ +------+-----------+------------+----------+--------+-----------+----------- + +[Footnote 3: Stock not used; dirty.] + +Discussion of the various cooks will be given in connection with the +descriptions of those paper tests in which the stocks from the cooks +were used, since a stock and its cooking condition can be judged +adequately only after it has been put through the various processes and +into the finished sheet of paper. + +The first test consisted in making four separate cooks, Nos. 293, 294, +295, and 296, of approximately 300 pounds each, dividing the total stock +into two parts and making two separate paper tests. The first test was +made primarily in order to learn some of the qualities and +characteristics of the stock and to get the machinery equipment adjusted +properly. The yield of fiber was not determined in this preliminary +test, since the knowledge of it was not essential at this stage of the +work. The cooked stock which was emptied into the drainer to be washed +free from black liquor was composed largely of whole pieces of hurds, +but only slight pressure between the fingers was required to crush the +pieces. In the case of wood, this condition ordinarily would indicate +undercooking, but might not in the case of hurds. Further observation on +the action of the cooked stock during subsequent processes was necessary +in order to judge of its quality or the suitability of the cooking +conditions. The total cooked stock, about 500 pounds, was divided into +two portions of 200 and 300 pounds, respectively, and work was continued +on them separately. The 200-pound test, designated as run No. 135, was +put into a 350-pound washing engine, washed one hour, and given a total +light brush of 2-1/4 hours. The washing removed a great amount of dirt, +but the engine did not reduce the hurd stock as much as was desired. +After heating the stock in the beater to 40 deg. C., it was bleached with +bleaching-powder solution, 94 gallons at 0.418 pound bleach per gallon, +equivalent to 19.7 per cent of the fiber. This percentage of bleach is +regarded as too high for stock intended for book-paper manufacture, and +subsequent cooks therefore were given harder treatment in order to +reduce this figure. After draining and washing free from bleach +residues, the stock was furnished in the beater with 13 per cent of +clay, 1 per cent of resin size, and 2.5 per cent of alum, was tinted +blue, given one hour's light brush, and pumped to the stock chest. When +running it on the paper machine, the Jordan refiner seemed to have +little effect in reducing shives of undertreated wood, which indicated +further the necessity of harder cooking. The furnish acted well on the +paper machine at 70 feet per minute, but appeared somewhat too "free" on +the wire. The paper produced from this test is of very low quality, due +to the improper preparation of the stock, lack of sufficient bleach, the +use of too small an amount of blue tinting, and the presence of an +excessive amount of dirt, sand, and shives. The excessive amount of dirt +and sand suggested the sieving of the hurds before cooking, and this was +performed in all subsequent cooks. + +The finish of the sheet is very poor, due to the fact that the calender +stack was composed of very light rolls which did not have a satisfactory +surface, yet the stack is known to be able to produce better finishes if +the proper stock is employed. + +Run No. 136 was made on the 300-pound portion of stock from cooks Nos. +293, 294, 295, and 296, and in essentially the same manner as run No. +135. The stock was washed one hour, but given a brush of three hours, +and this brush was harder than in run No. 135. Bleach to the extent of +19.8 per cent of the fiber was used, assisted by 1 pint of oil of +vitriol, and the resulting color was an improvement over that of run No. +135. After adding 13.5 per cent of clay and sizing with 1.1 per cent of +resin size, the furnish was given one-half hour's light brush, tinted, +and run on the machine, which was set at 70 feet per minute. This stock +acted better on the wire and gave no trouble on the machine, but it +still seemed to be impossible to reduce the wood shives by manipulation +of the Jordan refiner. The resulting sheet is an improvement over that +produced by No. 135, but is far from satisfactory. + +Run No. 138 was made from hurds which, as in all subsequent tests, were +sieved on a 11-1/2-mesh wire screen until practically all the loose dirt +and sand was removed, which operation caused a loss averaging 3 per cent +of the hurds. Stock from cooks Nos. 302 and 303 was used for this run +and the increased amount of caustic soda and the increase in the time of +cooking gave a stock of better appearance than those of preceding tests. + +The stock, amounting to 231 pounds dry weight, was washed and at the +same time given a light brush for one hour only, after which it was +bleached with 17 per cent of bleach without the addition of acid. Since +the preceding paper appeared somewhat weak and had a low tearing +quality, it was decided to use a furnish of 15.7 per cent bleached +sulphite and 84.3 per cent bleached hemp-hurd stock. After loading with +13.1 per cent of clay and sizing with 1.1 per cent of resin size, the +furnish was given a medium brush for one hour, tinted, and run on to the +machine at 70 feet per minute. The stock gave no trouble on the machine, +but it was impossible to judge the effect of the Jordan refiner, because +through an oversight the machine chest had not been cleaned since +previous use on an unbleached yucca material. It is believed, however, +that sheet No. 138 shows improvement in the preparation of the hurd +pulp. + +Run No. 139 was made from stock of cooks Nos. 304 and 305, in which +still more caustic soda was employed and the time and temperature of +cooking were increased, giving a yield of total fiber of 40.7 per cent +of the sieved or 39.4 per cent of the unsieved hurds. The cooked stock +still seemed to be undertreated, but it must be remembered that in +working with any new raw material it is impossible to know in advance +how the properly treated material should appear. A washing of one hour +was given while the roll was lowered from a light to a medium brush, +after which the stock was bleached with 17.1 per cent of bleach without +the aid of acid. Since sulphite stock improved the previous paper, this +bleached stock was used in a furnish of 16.6 per cent sulphite and 83.4 +per cent hurds, loaded with 16.7 per cent clay, sized with 1.4 per cent +resin size, given a medium brush of two hours, tinted, and run on to the +machine at 70 feet per minute. The Jordan refiner seemed to have little +effect in reducing shives and was therefore left "just off." No trouble +was experienced with the stock on the machine, and the sheet is an +improvement over previous samples. + +Run No. 140 was made from cooks Nos. 306 and 307, in which more caustic +soda was employed than in any previous cooks and at a higher +concentration, the fiber yields of which averaged 37.3 per cent of the +unsieved hurds. Not much improvement was apparent in the cooked stock, +in spite of the increased severity of cooking. The stock was washed and +given a medium brush for one hour, bleached with 11.9 per cent of +bleach, assisted with one-half pint of oil of vitriol, and made into a +furnish of 14.9 per cent sulphite and 85.1 per cent of the hurd stock. +After loading with 14.7 per cent of clay and sizing with 1.28 per cent +of resin size, the furnish was given two hours' medium brush, tinted, +and run on to the paper machine at 70 feet per minute. Again the Jordan +refiner did not seem to reduce the wood shives sufficiently, and it was +left "just off." No trouble which could be attributed to the stock was +experienced on the paper machine. The color of the resulting paper is +due to the use of too little blue in tinting and probably in some +measure to the use of too low a percentage of bleach. + +Run No. 141 was made from the stock of cooks Nos. 308 and 309 in +practically the same manner as run No. 140. The stock was washed and +brushed one hour, bleached (the record of the amount of bleach was +lost), made into a furnish of 14.7 per cent of sulphite and 85.3 per +cent of hurd stock, loaded with 14.9 per cent of clay, sized with 1.26 +per cent of resin size, given one hour at a medium brush, tinted, and +run on to the machine. The Jordan refiner was able to reduce the wood +shives to a somewhat greater degree than in previous runs and was held +at a medium brush. The stock acted well on the machine and produced a +sheet of better quality than any preceding, with the exception of the +color, which was due to using too small a quantity of blue. + +Among the cooks made for run No. 142 are Nos. 312 and 313, in which the +concentration of the caustic soda was raised to 113 and 116 grams per +liter and the percentage employed was also increased. In spite of these +increases the stock from these two cooks did not show any appreciable +improvement when dumped from the rotary. Stock from cooks Nos. 310, 311, +and 312 was given a medium brush and washing of one hour, bleached with +10.95 per cent of bleach, made into a furnish consisting of 15.2 per +cent of sulphite and 84.8 per cent of hurd stock, loaded with 15.2 per +cent of clay, sized with 1.28 per cent of resin size, given a medium +brush for one hour, tinted, and pumped to the stock chest. Stock from +cooks Nos. 313 and 314 was treated in exactly the same manner, except +that 11.4 per cent of bleach was used. It was pumped to the stock chest +and mixed with the furnished stock from cooks Nos. 310, 311, and 312. A +medium Jordan brush was given the stock and it acted well on the paper +machine, which was speeded to 75 feet per minute. There seems to be a +tendency in the hurd stock to crush a little at the "dandy roll," and +although the marks are not removed by the calender stack which was +employed in those tests it was found that one "nip" on the +supercalenders renders them practically imperceptible and it is believed +that the proper size and weight of calender stack would entirely remove +these marks. All of the papers produced up to this point are somewhat +lacking in the bulk desired in a book paper; therefore, in the two +following runs soda-poplar stock was included in the furnishes. + +In run No. 143 stock from cooks Nos. 315 and 316 was given a medium +brush and washing for one hour and was medium brushed for one hour more, +bleached with 11.3 per cent of bleach assisted with one-half pint of oil +of vitriol, made into a furnish of 16.5 per cent of sulphite, 22.3 per +cent of soda poplar, and 61.2 per cent of hurd stock, loaded with 22 per +cent of clay, sized with 1.38 per cent of resin size, given a hard brush +for one hour, tinted very strongly, and pumped to the stock chest. This +stock was beaten to a greater extent than in previous runs. The stock +was run on the paper machine at a speed of 75 feet per minute, using a +medium Jordan brush, and no trouble whatsoever was experienced. Not over +2 pounds of "broke" was produced during the whole run, and that was in +the "threading" of the machine. The color of the sheet is entirely +satisfactory for many uses. The wood shives apparently were reduced to a +satisfactory degree. Experienced paper makers commented very favorably +on the running of this furnish and the quality of the paper produced. + +Run No. 144 was intended as a duplicate of run No. 143. Stock from cooks +Nos. 317 and 318 was given a medium brush and washing for one hour and a +further medium brush of one hour, bleached with 11.4 per cent of bleach, +and made into a furnish composed of 15.5 per cent of sulphite, 23.5 per +cent of soda poplar, and 61 per cent of hurd stock, loaded with 21.4 per +cent of clay, sized with 1.17 per cent of resin size, hard brushed for +one hour, tinted by the expert colorer of the company, and pumped to the +stock chest. Stock from cooks Nos. 319 and 320 was treated in exactly +the same manner except that the stock was bleached with 12.1 per cent of +bleach and pumped to the stock chest to mix with the former furnish. The +stock acted very well on the machine, which was speeded to 75 feet per +minute, with the Jordan refiner set at a medium brush. The sheet is as +good, if not better, than that of run No. 143, and it is also a good +illustration of the extent to which proper tinting will enhance the +general appearance of a paper. The poor appearance of the samples of +previous runs is due largely to lack of proper tinting. Various degrees +of whiteness, however, are demanded by the trade. + + +=COMPARISON OF THE TESTS AND COMMERCIAL PRACTICE.= + +In work of this nature and on this scale it is practically impossible to +arrive at a cost figure which would be susceptible of commercial +interpretation, and in this preliminary publication nothing will be +attempted beyond a comparison of the process used with the hurds with +that process commercially applied to poplar wood. The process last used +with the hurds should not be regarded as final, satisfactory, or most +suitable, as it has been shown that progress was being made up to the +conclusion of the work. + +In comparing the method of using hurds with the method of handling +poplar wood, a difference is apparent on the delivery of raw material at +the mill. Ordinarily, poplar is received at the mill in the form of logs +about 4 feet in length, which may be stored in piles in the open. Hurds +very likely would be received baled, and it would seem advisable to +store them under cover for the following reasons: (_a_) Baled hurds +would probably absorb and retain more water during wet weather than logs +of wood, thereby causing excessive dilution of the caustic liquor; (_b_) +prolonged excessive dampness might create heating and deterioration +unless the hemp were properly retted; (_c_) wet hurds could not be +sieved free from sand and chaff. Should further work show that the first +two reasons need not be taken into consideration, the third objection +might be overcome by sieving the hurds before baling. Even then, it is +probable that baled hurds stored in the open would accumulate and retain +considerable dirt from factory chimneys, locomotives, and wind. Checked +pulp wood exposed in the open invariably suffers from these causes. + +In the preparation of the raw material for the digesters there is +likewise considerable difference between hurds and poplar wood. The +former apparently requires only a moderate sieving to remove sand and +chaff, which operation doubtless would require only a small amount of +labor and the installation of some simple machinery of low power +consumption. In preparing poplar for digestion, the 4-foot logs are +chipped by a heavy, comparatively expensive chipper of high power +consumption, after which the chips are sorted by sieving, the large +pieces being rechipped. There would be a noteworthy difference in the +installation, operating, and depreciation costs of the two equipments, +and this difference would counterbalance to a considerable extent the +difference in cost of raw material storage. + +It is possible that in the use of the chip loft more care would have to +be exercised in using hurds because of the tendency of the bast fiber to +cause lodgments, but this should not be considered a serious difficulty. + +The weight of hurds which are capable of being charged into a rotary is +a decidedly unfavorable factor. The weight of a cubic foot of hurds +varies somewhat with the proportion of bast fiber, but averages about +5.4 pounds, which, compared with a cubic foot of poplar chips at 8.93 +pounds, represents a digester charge of 60.5 per cent of the weight of +a poplar-wood charge, or, in terms of fiber capacity, the hurds charge +would yield 38.6 per cent as much fiber as the wood charge. The hurds +upon being baled for transportation may be broken and crushed to such a +degree that the weight of the charge may be increased, and it might be +found possible to increase the charge weight by steaming or by the +employment of tamping devices. This small weight of charge constitutes +one of the most serious objections to the use of hurds in paper +manufacture. + +In those tests in which the most satisfactory results were obtained, the +cooking conditions were 29.5 per cent of caustic soda at a concentration +of 107 grams per liter and a causticity of 84.0 per cent acting at a +temperature of 170 deg. C. for five hours, or a total time of seven hours. +The steam condensation in the rotary used for these tests was abnormally +high, due to the fact that the steam supply pipe was uncovered for a +considerable distance and the rotary was entirely uncovered. It is +believed, therefore, that a larger amount of caustic was necessary than +would otherwise have been the case. This belief is strengthened by the +quality of the waste liquor from one of the later cooks, which gave on +analysis 16.85 grams per liter of free caustic soda and showed a +causticity of 27.75 per cent. These data show that only 67.3 per cent of +the total caustic employed was actually consumed in the cooking +operation, which percentage is lower than obtains in practice. The stock +from this cook was bleached with 11.5 per cent of bleach. But even as +the figures stand, the comparison with poplar cooking practice is as +follows: 29.5 per cent caustic soda used as against 22 to 25 per cent; +107 grams per liter as against 100 to 110; 84 per cent causticity is +little different than obtains in practice; 170 deg. C. is about commercial +practice; five hours at pressure as against four to six hours; seven +hours' total time as against possibly six to eight hours; 11.5 per cent +bleach as against 8 to 10 per cent. Thus, it is evident that the cooking +conditions employed were slightly more severe and expensive than those +in commercial use with poplar wood. + +The yield of total fiber obtained from the hurds may be placed at 35 per +cent of bone-dry fiber calculated on the bone-dry weight of hurds used, +or 33.1 per cent of air-dry fiber calculated on air-dry hurds. The yield +of bleached fiber was not determined in this preliminary work, but may +be safely estimated as 30 per cent, which is low when compared with a +yield of about 47 per cent of bone-dry bleached fiber from bone-dry +poplar wood. It is believed quite possible that satisfactory cooking +conditions may be found which will give a higher yield than was obtained +during these tests. The stock should be classed as easy bleaching, and +11.4 per cent of bleach is a satisfactory figure, although a little +high. + +As to beating cost, in the last two and most satisfactory tests the +total washing and beating time was three hours, which may be about an +hour more than ordinarily is used in making papers of this grade, +although the practice varies to a considerable extent. + +In regard to furnish, there is such a diversity of practice that it is +difficult to make a comparison, but if the hurd stock can be produced as +cheaply as soda-poplar stock, the furnish used in these last two tests +should be regarded as satisfactory to the book and printing paper +manufacturer. + +The finish of the paper was not all that might be desired, but that was +due almost entirely to the calender stack available for the work, which +was composed of nine light rolls, many of which were about 6 inches in +diameter and which had not been reground for some time. From a small +test on a large calender stack it was readily shown that the paper +produced is capable of taking a satisfactory finish. + +This comparison, satisfactory in many respects, develops two factors +which are decidedly unfavorable to hemp hurds, namely, raw-material +storage and digester capacity, and they must be taken into full account +in considering the paper-making value of this material, although it +should be recognized that investigation may result in the material +improvement of these conditions. Moreover, it is not at all improbable +that further investigation would develop more satisfactory treating +conditions and more suitable furnish compositions, and the belief in +this possibility is strengthened by the fact that material progress was +being made at the conclusion of this preliminary work. + +Calculations on the raw material and acreage for a permanent supply for +a pulp mill producing 25 tons of fiber a day for 300 days per annum, or +7,500 tons per annum, give the comparison between hurds and wood shown +in Table II. + + +TABLE II.--_Comparison between wood and hemp hurds._ + +-----------+-------------+--------------+-----------+-------------------- + | | | | Acres required for + | | | | sustained supply. + | | | |---------+---------- + | | Raw material | Annual | | +Material. | Pulp yield. | required per | growth | For | For 1 ton + | | year. | per acre. | 25-ton | of fiber + | | | | mill. | per year. +-----------+-------------+--------------+-----------+---------+---------- +Wood | Two cords | 15,000 cords | 0.37 cord | 40,500 | 5.4 + | yield 1 ton | | (about | | + | of fiber. | | 0.55 ton).| | + | | | | | +Hemp hurds | One ton | 25,000 tons | 2.5 tons | 10,000 | 1.33 + | yields 600 | | | | + | pounds | | | | + | of fiber. | | | | +-----------+-------------+--------------+-----------+---------+---------- + +The most important point derived from this calculation is in regard to +areas required for a sustained supply, which are in the ratio of 4 to 1. +Every tract of 10,000 acres which is devoted to hemp raising year by +year is equivalent to a sustained pulp-producing capacity of 40,500 +acres of average pulp-wood lands. In other words, in order to secure +additional raw material for the production of 25 tons of fiber per day +there exists the possibility of utilizing the agricultural waste already +produced on 10,000 acres of hemp lands instead of securing, holding, +reforesting, and protecting 40,500 acres of pulp-wood land. + +The annual growth per acre, although decidedly in favor of hurds, has +little bearing on the project, because the utilization of the hurds is +subordinate to the raising of hemp, and the paper manufacturer probably +could afford to use only hurds resulting from the hemp industry. + + +=PHYSICAL TESTS OF THE PAPERS PRODUCED.= + +Samples of paper produced in the seven tests were submitted to the +Leather and Paper Laboratory of the Bureau of Chemistry. The report of +that bureau on its tests is given in Table III. + + +TABLE III.--_Report of the Leather and Paper Laboratory of the Bureau of +Chemistry on papers manufactured from hemp hurds._ + +-----------+-----+------+-------------------+----------+ + | | | Weight of 500 | | +Laboratory | Run | | sheets. |Thickness,| +No. | No. | Ash. +---------+---------+ 1/10000. | + | | | | | | + | | |25 by 38.|25 by 40.| | + | | | | | | +-----------+-----+------+---------+---------+----------+ + | |_Per | | | | + | | ct._ |_Pounds._|_Pounds._| | +31570 | 144 | 13.9 | 48 | 50-1/2 | 33 | +31571 | 143 | 14.5 | 49 | 51-1/2 | 35 | +31572 | 142 | 9.5 | 49-1/2 | 52 | 33 | +31573 | 141 | 10.9 | 48 | 50-1/2 | 38 | +31574 | 140 | 11.4 | 42 | 44 | 30 |[Transcriber's +31575 | 139 | 13.4 | 55 | 58 | 40 | note: Table III +31576 | 138 | 10.4 | 56 | 59 | 40 | continues below] +-----------+-----+------+---------+---------+----------+ + +-----------+--------------------------+----------+------------------------- + | Strength (Mullen). | | Folding endurance. +Laboratory | | Strength | +No. +--------+--------+--------+ factor +-------------+----------- + | | | |(25 by 40,| | + |Average.|Maximum.|Minimum.| 500). |Longitudinal.|Transverse. + | | | | | | +-----------+--------+--------+--------+----------+-------------+----------- + | | | | | | + | | | | | | +31570 | 15.0 | 17.0 | 11.0 | 0.30 | 5 | 3 +31571 | 14.0 | 14.0 | 13.0 | .28 | 4 | 4 +31572 | 19.0 | 20.0 | 19.0 | .37 | 8 | 6 +31573 | 16.5 | 18.0 | 11.0 | .33 | 10 | 8 +31574 | 14.5 | 16.0 | 13.0 | .33 | 7 | 6 +31575 | 19.5 | 20.0 | 17.0 | .34 | 8 | 5 +31576 | 20.0 | 20.0 | 19.0 | .34 | 23 | 15 +-----------+--------+--------+--------+----------+-------------+----------- + + +There is no system of numerically recording the general appearance and +"look through" of a paper, but it can be stated that only papers Nos. +143 and 144 are satisfactory in these respects, the other samples being +more or less thickly specked with shives. The general character and +tests of these papers correspond very closely with No. 1 machine-finish +printing paper, according to the specifications of the United States +Government Printing Office, which call for a sheet not exceeding 0.0035 +inch in thickness, strength not less than 12 points, free from +unbleached or ground wood pulp, and ash not over 10 per cent. The +strength factor of such papers is about 0.28. The ash should not be over +10 per cent for this grade of paper, but in spite of the larger amount +used the physical tests are sufficiently high. It is to be noted that +the physical tests of samples Nos. 138 to 142, inclusive, are higher +than in Nos. 143 and 144, in which 23 per cent of soda poplar was used, +which shows clearly that hemp-hurd stock imparts strength and folding +endurance to a greater extent than does soda-poplar stock. From these +preliminary tests it would be concluded, therefore, that hemp-hurd stock +acts similarly to soda-poplar stock, but will produce a somewhat harsher +and stronger sheet and one of higher folding endurance. Undoubtedly, +there is more dirt in the samples than would be tolerated by the trade, +but this was to be expected, since in this preliminary work the raw +material was sieved by hand screens instead of by automatic machines +which would sieve more thoroughly. + + +=CONCLUSIONS.= + +There appears to be little doubt that under the present system of forest +use and consumption the present supply can not withstand the demands +placed upon it. By the time improved methods of forestry have +established an equilibrium between production and consumption, the price +of pulp wood may be such that a knowledge of other available raw +materials may be imperative. + +Semicommercial paper-making tests were conducted, therefore, on hemp +hurds, in cooperation with a paper manufacturer. After several trials, +under conditions of treatment and manufacture which are regarded as +favorable in comparison with those used with pulp wood, paper was +produced which received very favorable comment both from investigators +and from the trade and which according to official tests would be +classed as a No. 1 machine-finish printing paper. + + + + + + +End of the Project Gutenberg EBook of Hemp Hurds as Paper-Making Material, by +Lyster H. Dewey and Jason L. Merrill + +*** END OF THIS PROJECT GUTENBERG EBOOK HEMP HURDS AS PAPER-MAKING *** + +***** This file should be named 17855.txt or 17855.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/7/8/5/17855/ + +Produced by K.D. 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