JACK PINE AND HEMLOCK FOR MECHANICAL PULP. 21 



HEMLOCK PULP. 



Plates XI, XII, and XIII show hemlock fibers which were obtained 

 during the tests. Undoubtedly the most notable feature is the large 

 amount of fine material present as compared with the jack pine sam- 

 ples. Hemlock grinds short and fine to a far greater extent than 

 either spruce or jack pine. While there are a great many long fibers 

 present, they are not sufficient in number to give a strong and tough 

 pulp. A certain amount of short material is necessary, however, for 

 news paper, and it is this material which gives a good finish. The 

 finish on the paper made from the hemlock pulp, commercial run No. 

 8, was exceedingly good; in fact, the superintendent of the mill where 

 the sample was run pronounced it better than the standard news. It 

 will be seen that there is a regular gradation in the length of fibers 

 from the long to the almost powder form. On certain of the illustra- 

 tions of hemlock fiber black spots composed of a great deal of fine 

 fiber will be noticed. These are the result of drying the pulp before 

 making slides, it being impossible entirely to beat out the fiber after 

 drying. When the material was in the form of pulp laps there was 

 no marked difference in the pulps. However, as with the jack-pine 

 samples, only the better grades of pulp obtained are shown. The 

 sample of pulp illustrated in Plate XIII, figure 2 (commercial run No. 

 50), is fairly representative of the pulp which it is possible to make 

 from hemlock under the conditions described. 



MIXED PULPS. 



Plate XIV shows three photomicrographs of fibers obtained under 

 exactly the same conditions of pressure, speed, and surface of stone. 

 The temperature and other minor variables were also kept as nearly 

 alike as possible. 



Figure 1 shows fibers obtained by grinding hemlock in two of the 

 grinder pockets and spruce in the third (run 46a). Upon determina- 

 tion it was found that the pulp contained 34 per cent spruce and 66 

 per cent hemlock. Figure 2 shows hemlock fiber obtained under the 

 same conditions (run 466) as the first test, and figure 3 shows a number 

 of spruce fibers (run No. 46c). The hemlock fiber is considerably 

 shorter than the spruce and there are more shives present. In the 

 composite sample the hemlock is decidedly in evidence. 



Plate XV shows three fibers obtained by grinding different woods 

 in different pockets of the pulp grinder. Commercial run No. 46a is 

 composed of a mixture one-third spruce and two-thirds hemlock; 

 commercial run No. 51 is composed of one-third jack pine, one-third 

 spruce, and one-third hemlock; commercial run No. 52 of one-third 

 jack pine and two-thirds hemlock. All of these pulps when in the 



