32 BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 
remarkably good results, and, bemg available in large quantities, 
should serve as a raw material for this purpose. Tests made on 
sheets composed entirely of boiled and steamed ground-wood pulp 
show that wrapping papers which will test from 0.50 to 0.75 of a 
point to the pound are easily produced. Wrapping papers of this 
kind are inclined to be brittle and do not have sufficient strength in 
tearing or folding without the addition of a small amount of chemical 
fiber. 
Resinous woods, if given a mild steaming or boiling treatment prior 
to grinding, are rendered much more free from pitch, although the 
pulp is made very soft and darkened to some extent. The use of 
this method for the production of news print paper would undoubt- 
60 420 
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B HORSEPOWER PER TON PER POINT PER POUND [MULLEN TEST) 
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SSSI aT OU AE (ST 
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A BREAKING LENGTH PER HORSEPOWER PER TON = METERS 
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100 120 - $40. — 180 a 220 
HORSEPOWER PER TON OF PuLP [50RE DRY] 
Fic. 22.—Relation of strength of paper per horsepower to power consumption per ton of pulp. 
edly be costly on account of the handling necessary, the cost of steam- 
ing, and the loss in yield. 
SUMMARY OF INFLUENCE OF GRINDING AND COOKING CONDITIONS IN THE PRODUC- | 
TION OF SPRUCE PULP. ; 
The experiments conducted by the Forest Service, both in cooking © 
spruce prior to grinding and in varying conditions of producing pulp, ~ 
have led to the following conclusions: 
COOKED WOOD. 
(1). Cooking spruce prior to grinding results in a stropger fibered — 
pulp, although at least 25 per cent more power per ton is required 
than is used in grinding untreated wood. The horsepower consump- 
tion per ton when grinding under conditions of varying cylinder pres- 
sure decreases to a minimum at approximately 65 pounds pressure 
on a 14-inch cylinder; this holds for dull or sharp stones. 
