10 BULLETIN 152, U. S. DEPARTMENT OF AGRICULTURE. 



PULP. 



In 1905 hemlock formed 11.8 per cent of all the wood used for 

 pulp. In 1906 and 1907 it supplied 14 per cent of the total amount; 

 in 1908, 17 per cent; in 1909, 14 per cent; and in 1910, 15 per cent. 

 During the latter year its consumption was 50 per cent greater than 

 in 1905. 



Hemlock pulp is used for news, wrapping, and other cheap grades 

 of paper, and is manufactured chiefly by the sulphite process. In 

 this process the wood is first chipped and then cooked in a solution 

 of calcium sulphite, which frees the fibers by dissolving the sub- 

 stances that unite them. The dissolved substances comprise about 

 half the original weight of the dry wood, without bark. Hemlock 

 also furnishes a small amount of ground wood pulp, but the great 

 bulk of this is spruce. Ground wood is inferior to chemical pulp, 

 since the fibers become broken in grinding, while the pulp contains 

 the useless constituents which are dissolved out in the chemical 

 process. As a result it is mealy and less interlaceable, especially in 

 the case of hemlock, the fibers of which are shorter than those of 

 spruce. In spite of this, a very serviceable grade of news paper can 

 be made from hemlock pulp, 75 per cent ground and 25 per cent sul- 

 phite, with almost the strength, finish, and appearance of that made 

 chiefly of spruce. 1 



Since the value per ton of ground wood is only about $15, as com- 

 pared with $47 for sulphite pulp, the former is used as the basis for 

 news and other cheap grades of paper, to which a small amount 2 of 

 sulphite pulp is added for strength. Spruce once furnished prac- 

 tically all of both kinds of pulp, and still supplies 90 per cent of the 

 mechanical pulp. Its increasing cost has brought about the use of 

 cheaper woods in the sulphite process, during which so much of the 

 volume is lost. Spruce now supplies less than 60 per cent of the sul- 

 phite pulp, while hemlock supplies about 25 per cent. The propor- 

 tions of hemlock manufactured by the various processes for the six 

 years from 1905 to 1910, inclusive, were — 



Per cent. 



Sulphite process - 94. 75 



Mechanical process 4. 5 



Soda process 7 



Sulphate process 05 



100. 00 



Hemlock pulpwood is marketed both as cordwood and in the log. 



In Wisconsin pieces 8 inches and over at the small end are ordinarily 



cut in log lengths and sold by the thousand board feet, 1,000 



board feet usually being considered equivalent to 2 cords. Pieces 



i J. H. Thickens: "Experiments with Jack Pine and Hemlock for Mechanical Pulp." Dept. of Agri- 

 culture, Forest Service Forest Products Laboratory Series, June 11, 1912. 



2 The usual proportion is from 70 to 84 per cent ground pulp to from 16 to 30 per cent sulphite. 



