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.)
The broken pieces of wood contained in the hurds varied in length from mere particles which were somewhat finer than sawdust to pieces about 3½ 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 [ -12- ]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.