Lyster H. Dewey

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ Where machine brakes are used, the hemp stalks are brought to the machine as grain is brought to a thrashing machine, and the hurds -4- 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 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. ”

“ 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. ”

“ 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. ”

“ 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 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. ”

“ 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. ”

“ 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. ”

“ 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 21⁄2 tons of hurds per acre may be taken as a fair average. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”