26 ‘BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE, 
of the stone. Stronger pulp is obtained, however, at conditions of | 
low speed and high pressure than is obtained at conditions of high | 
speed and low pressure. It is believed, however, that the pressure is | 
more responsible here than the speed. Figure 19 shows that the 
strength of paper, when the same amount of power is applied, is much | 
less when the power is utilized at high speed and low pressure than | 
at high pressure and low speed. | 
TEMPERATURE OF GRINDING. 
temperature. It is true that the production in 24 hours is less when | 
0 BB SS a fa ek fs es ech ees ees nea sd olde ne odinsl ed ce le 
Yee ape | SPs Sea [nls a 
(8 WE eB a ee en ee i NU Pf Safe | 
GE RF a | OP a Sp 
pea | aS eT ESTE ae ae aE TTT fe 
CE Se eee ie euss paieeaa a 
ai ea 
7 
240 
HERR aps. ia] Reet 
20 798 a 
sreauiiia baeesbaeS une 7 
Fic. 16.—Effect of steaming pressure on speed—horsepower to grinder constant. (Spruce runs 233 to 242, 
inclusive.) 
440, 
grinding cold than when the hot process is used, but the variation of 
the temperature from 125° to 190° F. does not materially influence | 
the rate of production. The pulp is somewhat finer when ground cold, | 
but there is not as much difference between pulps manufactured by. | 
the cold and hot processes as is generally believed. 
OTHER FACTORS. 
Among the other factors which influence the power consumption, 
production in 24 hours, and the quality and yield of pulp are the 
amount of seasoning the wood has undergone before grinding, the 
dry weight per cubic foot, the size of bolts, and the rate of growth. 
It is easier to grind green wood and secure a satisfactory pulp than 
it is to grind seasoned wood. Seasoned wood almost invariably 
