GROUND-WOOD PULP. 17 
Tests on papers made from steamed and unsteamed woods show 
that the unsteamed pulps do not give as high percentage stretch 
as the steamed, even though the unsteamed pulps were mixed with 
20 per cent of bleached spruce sulphite. Pulps made from cooked 
woods should be given satisfactory beating treatments to make them 
usable for different purposes. Like chemical pulp, there is a marked 
influence on the resultant paper when the pulps are given different 
‘beating treatments. The sheets become more brittle after a pro- 
longed beating, but give high strength tests. 
: THE EFFECT OF GRINDING STEAMED AND UNSTEAMED WOODS UNDER 
if VARIABLE CONDITIONS. 
SURFACE OF STONE. 
There is shown in figure 9 a series of curves on steamed and un- 
‘steamed woods which were conducted on different surfaces of stone. 
‘It is evident that the horsepower consumption per ton when steamed 
“wood is used decreases to a minimum value at a grinder pressure of 
_ approximately 65 pounds per square inch on a 14-inch cylinder, 
“regardless of the surface which is used. The contrast in the form of 
' ihe curves for steamed and unsteamed wood is shown in this same 
i figure. Curves 2 and 3 were run under exactly the same conditions, 
i ‘except that in one case steamed wood and in the other unsteamed 
wood was used as a raw material. 
Upon the condition of the surface of the pulp stone depends, to a 
great extent, the power consumption per ton of pulp made, the rate 
of production, and the quality of the resultant material. The pulp 
stone used in the tests was burred in many different w ays, and it 
"was generally found that if the grit were brought to the same con- 
dition of sharpness, the power consumption, rate of production, and 
quality of pulp would be practically the same. When the stone is 
"rough but the sand particles are not sharp, a coarser pulp is produced 
4 which acts more free on the wire of the paper machine. It was also 
found that regardless of the degree of sharpness of the stone it was 
impossible to aiutein pulp for news print if the expenditure of power 
temain 50 horsepower per ton. 
_ Figure 10 shows by curves obtained at different pressures the 
‘relation of three different surfaces of stone to the power consumption 
‘per ton, power to the grinder, and production in 24 hours. These 
typical curves show how greatly the above-mentioned factors are 
“influenced by varying the sharpness of the pulp stone. 
Plates I and Il show the effect of different degrees of sharpness of 
stone on the quality of pulp prodticed as represented by the character 
of fibers. Plate I, figure 1, shows the fiber produced on the sharpec 
medium grit stone with the consumption of a small amount of power, 
14852° 
5a ge ag ge 
