GKOUND-WOOD PULP. 17 



Tests on papers mado from steamed and unsteamed woods show 

 that the unsteamed pulps do not give as high percentage stretch 

 as tho steamed, even though the unsteamed pulps were mixed with 

 20 per cent of bleached spruce sulphite. Pulps mado 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 

 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 

 the curves for steamed and unsteamed wood is shown in this same 

 figure. Curves 2 and 3 were run under exactly the same conditions, 

 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 ways, 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 

 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 obtain pulp for news print if the expenditure of power 

 remain 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 II show the effect of different degrees of sharpness of 



stone on the quality of pulp produced as represented by the character 



of fibers. Plate I, figure 1, shows the fiber produced on the sharper 



medium grit stone with the consumption of a small amount of power, 



14852°— Bull. 343—16 2 



