Contributor's Note: The following article is provided courtesy of the Business Alliance for Commerce in Hemp (BACH), Historic Reprint Series. -=]*[=- --Excerpted From U.S. Department of Agriculture Bulletin #404-- By Jason L. Merrill US Dept. Of Agriculture Paper-Plant Chemist October 14, 1916 INTRODUCTION: Page 7 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 in 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. COMPARISON TO WOOD: Page 24 The most important point derived from our calculation is in regard to areas required for 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,m 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. ADVANTAGES OF HEMP HURDS: Page 9 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 happened 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 over- cropping, which has contributed so much to the present high hand 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, the competition would be strongest from the eastern mills. In fact, the hurd stock might very possibly meet with favor as a bookstock furnish in the Michigan and Wisconsin paper mills, which are within the sulphite fiber-producing region, where a considerable extension of the hemp industry is anticipated. CONCLUSIONS: Page 25 There appears to be little doubt that under the present system of forest use and consumption the present supply cannot 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. Semi-commercial 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 which according to official test would be classed as a No.1 machine finished printing paper. TECHNICAL REPORT ON OPERATIONS INVOLVED IN PERFORMING A TEST: Page 13 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% 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%. 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% causticity. Sufficient caustic solution was added to furnish 25% or 30% 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 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 C the pressure was usually 115 or 120 pounds instead of 100 pounds, due to air and gases closed 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 this, the rotary was stopped and steam relieved until the pressure was reduced to zero, the head was removed and the stock was emptied into a tank underneath, measuring 5 1/2 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 water was sucked from the stock in the drain tank by means of a vacuum pump communicating with the space between the bottom and the false perforated bottom, leaving the fiber with a very uniform moisture content throughout its entire mass 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% 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 five inches. For this reason, the moisture control of the stock will vary from 65% to 85%. 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 C, and a solution of commercial bleaching powder was added in the quantity judged to be as necessary, after which the stock was pumped to a large wooden tank, to remain and bleach overnight. If the stock was bleached sufficiently white it was drained and washed from bleach residues. If not, more bleach was added until a good color was obtained. The bleaching powder used was estimated to contain 35% of available chlorine, 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 consumption of bleach will be held within certain limits, depending on the raw materials used and the quality of the paper to be produced. In these tests it was desired to cook the hurds so that consumption of bleach would not be over about 10% 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." 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. PAPERMAKING: The term "papermaking," 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 is often used for the production of paper for filling regular commercial orders. The machine is designed to cause the water suspension to 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. -=]*[=- This condensation presented as a public service by: BUSINESS ALLIANCE FOR COMMERCE IN HEMP For more on the many uses of hemp, send $1 & a large, stamped self- addressed envelope. For a catalog of documents, send $2 to BACH, POB 71093, L A, CA 90071-0093 213/288 4152 -=]*[=- END