JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 7 



WHY JACK PINE AND HEMLOCK HAVE NOT FEEN USED. 



There is much doubt as to exactly why the pulp industry has 

 neglected to use hemlock and jack pine for the cheaper grades of 

 paper. It seems to be the general impression that hemlock grinds 

 so fine and short that there is a great loss in conversion. It has been 

 said that the yield obtained is in many instances only three-fifths of 

 that from an equal amount of spruce. This loss in grinding hemlock 

 has not been in evidence during the tests. 



The pitch in jack pine is undoubtedly responsible for the lack of 

 attention paid to that wood. This, however, can be removed by 

 steaming or soaking, and such treatments will be taken up in future 

 experiments. 



In all the experiments the yields secured from the different woods 

 were in direct proportion to their bone-dry weight per cubic foot. 

 It is therefore to be expected that the yields from jack pine and 

 hemlock will be less per unit of volume than those from spruce, since 

 the two first woods are considerably lighter in weight. On the basis 

 of weight, however, there appears to be relatively little more loss in 

 converting hemlock or jack pine into pulp than in converting spruce. 



The fiber obtained from the ground hemlock and jack pine has 

 been considered unsatisfactory on account of its shortness. Yet it 

 has been found long enough for use in cheap papers. 



One who is accustomed to handling spruce ground wood will not 

 be favorably impressed with the appearance of either hemlock or 

 jack pine pulp. This is particularly true of the hemlock sheet. 

 Both pulps are somewhat softer in texture than spruce, and, alto- 

 gether, are not as pleasing in appearance as the present commercial 

 product. 



Another point which may account for the lack of attention paid 

 to hemlock and jack pine is the care which must be exercised in 

 grinding them. It is possible to obtain a grade of pulp from spruce 

 which is suitable for most purposes without using a great deal of 

 care in the preparation of the surface of the pulp stones. In the 

 grinding of jack pine and hemlock, especially hemlock, on the other 

 hand, great care must be exercised in bringing the stone to the correct 

 degree of sharpness, since these woods will grind to powder if the 

 surface is as sharp as the one ordinarily employed in grinding spruce. 



Yet notwithstanding certain shortcomings the fact remains that 

 it is possible to obtain hemlock and jack pine pulps commercially 

 which are suitable for the cheaper grades of paper. 



