48 



BULLETIN 343, U. S. DEPAETMENT OF AGBICULTTJEE. 



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, Alpine 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 

 grinding, 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. 



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. 



