CONTROL OF DECAY IN PULP AND PULP WOOD 
15 
both runs. The temperature of grinding varied between 120 and 
180° F. (49 to 82° C). After the separated screenings were weighed 
the pulp was run over the wet machine and the dry weight calculated. 
The essential data obtained from these tests are shown in Table 1. 
Table 1. — Data on the grinding of sound and decayed spruce 
Quantity of wood pieces. 
Weight of rough wood _. pounds. 
Weight of rough wood, oven-dry 3 do... 
Loss in barking, based on oven-dry wood per cent. 
Weight of barked wood, oven-dry pounds. 
Yield of pulp, oven-dry weight do... 
Yield of oven-dry pulp, based on oven-dry barked wood per cent. 
Yield of oven-dry pulp, based on oven-dry rough wood do... 
Sound 
Decayed 
wood, 
wood, 
sample 1 
sample 2546 
1140 
* 250 
17, 920 
18, 839 
10, 720 
12,600 
32.4 
31.3 
7,250 
8,650 
6,826 
6,783 
94.2 
78.4 
63.7 
53.8 
12-foot lengths. 
2 8-foot lengths. 
3 Computed from moisture samples. 
YIELD AND QUALITY OF PULP 
The results of this particular trial indicate a yield of 94.2 per cent 
in the case of the sound and of 78.4 per cent in the case of the decayed 
wood, on the basis of oven-dry weights in each case. Decay thus 
accounts for a loss of 15.8 per cent. 
A sample of the pulp from each grinder run was shipped to the 
Forest Products Laboratory for physical and microscopic examina- 
tion and for paper-making trials. Samples were also placed in moist 
storage for further observation, as described later. 
Sedimentation tests indicated that the pulp made from decayed 
wood was slightly freer than that made from sound wood, although 
the difference was not marked. Microscopic examination of the 
average length of fiber particles showed 1.57 millimeters for the 
sound in comparison with 1.27 millimeters for the decayed material. 
The decayed pulp contained about twice as much debris, in the form 
of very small particles evidently produced by pulverizing the infected 
wood in the grinding. A large percentage of this debris would, of 
course, be lost during conversion on the paper machine, so that white 
water losses from decayed pulp should be larger than for sound pulp. 
The stock was run into 100 per cent ground-wood sheets without 
the use of size, alum, or color. Physical tests on the papers, as 
shown in Table 2, indicate that both stocks, in so far as these runs 
would show, were of about the same strength. The pulp made from 
decayed wood, however, contained the larger number of shives and 
was decidedly the darker of the two in color. 
Table 2. — Data on waterleaf papers made from sound and from decayed 
spruce woods 
Sample 
No. 
Description 
Weight 
of ream, 
24 by 
36—500 
Points 
per 
pound 
per ream 
Average 
breaking 
length 
Average 
stretch 
Tempera- 
ture 
Humid- 
ity 
1AA. .. 
2AB. „ 
From sound wood, No. 1 
From decayed wood, No. 2546... 
Pounds 
47 
48 
0.304 
.304 
Meters 
2,760 
2,610 
Per cent 
1.4 
1.3 
o F 
87 
85 
Per cent 
61.5 
64.0 
