28 



BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 



The rate of growth seems to have little effect upon the power 

 consumption or rate of production. When the wood is. of large 

 diameter it is necessary to split a considerable portion of it and more 

 or less binding is caused, this resulting in a higher power consump- 

 tion per ton of pulp. The yield and quality are both slightly in- 

 fluenced by the rate of growth of the wood. The yield is lower from 

 wood of rapid growth than from wood which has grown slowly. The 

 pulp is softer when rapid-growth wood is used, although the strength 

 is practically the same. Generally woods which are highly lignified 

























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Fig. 18. — Relation of power consumption and production to pressure and speed — horsepower to grinder 

 constant. (Tamarack runs 62 to 68, inclusive.) 



yield shorter fibered pulps than those having large amounts of 

 sapwood. 



The condition of the wood as regards decay has a marked effect on 

 the pulp. With the use of partially decayed wood the yield of pulp 

 from a cord is greatly decreased, and while the wood grinds faster 

 than entirely sound wood, giving an increased production and a cor- 

 respondingly lower power consumption per ton of pulp, the pulp 

 consists principally of extremely short fibers and wood flour, which 

 greatly decrease its strength. (Spruce runs 255 and 256.) At the 

 same time the color is materially darker than that of the pulp pro- 

 duced from sound wood. 



