10 BULLETIN 950, U. S. DEPARTMENT OF AGRICULTURE. 



SUITABILITY FOR PULP AND PAPER. 



So far as suitability of species for pulp making is concerned, it 

 should be sufficient to point to the British Columbia and Pacific 

 Xorthwest pulp mills now operating on Sitka spruce and western 

 hemlock. At times the hemlock alone is used, and it is said to 

 prove as satisfactory as in mixture with quick-cook sulphite fiber, 

 as far as quality of product is concerned. In addition to newsprint, 

 only a few grades of building and mill wrapping paper are made at 

 the British Columbia plants; but hemlock-spruce sulphite fiber is 

 shipped to outside mills for the production of bond, manila, tissue, 

 pure-fiber printing, and other high-grade papers requiring a strong, 

 tough, white fiber. 



Western hemlock and spruce are the standard mechanical and sul- 

 phite pulpwoods for the United States mills in the Pacific North- 

 west also, the hemlock being consumed in greater amounts than any 

 other single species. In 1918, 145,583 cords of hemlock pulpwood 

 and 35,385 cords of spruce was consumed in Washington, Oregon, 

 and California. Of ground wood pulp the hemlock, mixed with 

 spruce and cottonwood, amounts to 20 to 50 per cent of the total, and 

 the yield for the mixed species is about 1,850 pounds of air-dry pulp 

 per cord. Of pulp cooked by the sulphite process alone, the yield 

 is about 1,050 pounds per cord. The spruce (75 per cent), mixed 

 with black cottonwood (25 per cent), affords a yield per cord of 

 about 950 to 1,000 pounds of bleached soda pulp suitable for the 

 highest grades of book and writing papers made from wood. From 

 these three woods the following papers are made : Manila, cartridge, 

 express, bag, fiber wrappings, news, tissue, fruit wrap, toweling, 

 sheathing, book, label, writing, and related papers. 



The above facts show that the two principal species concerned are 

 both commercially suitable for mechanical and sulphite pulps (in- 

 cluding high-grade Mitscherlich fiber), and the papers that are 

 usually made from them, as before specified. 



While the consensus of practical opinion is that the spruce is 

 somewhat the better pulpwood of the two, the following condensed 

 summaries of some Forest Service semicommercial tests 6 at the 

 Forest Products Laboratory, at Madison, Wis., carried on for a 

 period of 10 years, afford a good opportunity for a comparison of 

 them. The slightly greater weight of the hemlock per unit volume 

 of prepared wood would usually be offset in commercial practice by 

 the greater loss in cleaning. Yields are air-dry weight per cord 

 containing 100 cubic feet of solid wood. 



6 See " Paper," July 30, 1919. 



