GROUND- WOOD PULP. 



45 



Through a mistake in shipment a quantity of white pine (Pinus 

 strobus) was received at the laboratory. It had not been the inten- 

 tion to test this wood, since its value for lumber eliminates it from 

 consideration as a possible substitute for spruce. Tests were made 

 on it, however, since it was at hand. It can be ground on a fairly 

 sharp stone to yield fibers of good strength and excellent color. The 

 pulp contains a considerable amount of pitch, and, like that from the 

 other pines, is inclined to be soft. The yield was approximately 

 1,885 pounds per hundred cubic feet of solid rossed wood. 



THE SPRUCES. 



Engelmann spruce (Picea engelmanni) can be ground under the 

 same conditions used for white spruce. The pulp has an excellent 

 color and a long strong fiber. The fact that the wood ground at 

 the laboratory was in a green state undoubtedly made it easier to 

 produce a good grade of pulp. Wood 

 obtained from Colorado in the form of 

 small logs showed no difference in quality 

 from similar material obtained from Mon- 

 tana, though the latter, owing to its 

 greater weight per cubic foot, yielded 

 about 2,250 pounds of pulp (bone dry) 

 per hundred cubic feet of rossed wood 

 against 2,000 pounds for the Colorado 

 material. 



Sitka spruce (Picea sitchensis) yields a 

 pulp of very good quality, though not 

 equal to that from white spruce. Although 

 the wood can be ground under practically any condition of speed, 

 sharpness of stone, and grinder pressure, the fibers are not as fine 

 and long as those of the white spruce. In color, moreover, Sitka 

 spruce pulp is inclined to be grayish. The wood tested was cut during 

 the latter part of April and contained considerable pitch. It undoubt- 

 edly would have run better had it been cut earlier in the year. The 

 yield was 2,100 pounds per hundred cubic feet of solid rossed wood, or 

 about 200 pounds less than that from an equal amount of white 

 soruce. 



Fig. 33.— Western larch (Larix occi- 

 dcntalis). 



THE HARDWOODS. 



Aspen (Populus tremuloides) requires the consumption of a large 

 amount of power to produce pulp which will run satisfactorily on the 

 wet machine. If the pulp stone is too sharp or a less amount of 

 power is used, the pulp will be very short. When mixed with spruce, 

 however, it operates very satisfactorily. Aspen pulp possesses good 



