48 BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 
on 
WOODS STEAMED PREVIOUS TO GRINDING. 
In addition to the tests on untreated wood, other tests were made 
on steamed material. Practically all of the conifers yielded fairly — 
strong, brownish-colored pulps suitable for the production of board 
and cheap grades of brown wrapping paper. Balsam fir, noble fir, 
amabilis fir, Alpme fir, and white and Engelmann spruce pulps 
showed longer fibers and felted somewhat better than those from the — 
other woods. When steamed all of the conifers required the con-— 
sumption of a relatively large amount of power for the production of 
satisfactory pulps. This was not the case, however, with aspen and — 
* 
Fig. 36.—Jack pine (Pinus divaricata). 
white birch, which produce much stronger pulps when treated before 
erinding, the product comparing favorably in color and toughness 
with spruce pulp. The fibers of the aspen and white birch were 
shorter, it is true, than those of spruce, but the felting qualities of the 
hardwood pulps are better than those of spruce pulp. Steamed aspen — 
and white birch can be ground with a comparatively small amount of 
power to produce the kind of pulp just described. 4 
A heavy loss in wood substance was noted in the case of all the | 
species tested except western larch. The fibers of the latter wood 
seem to become tougher as the result of cooking and do not grind up — 
to a fine powder which passes through the meshes of the cylinder 
mold. 
