30 BULLETIN 1298, U. S. DEPARTMENT OF AGRICULTURE 
sisted of freshly ground pulp. The cooperator described these 
pulps as follows: 
One lot is freshly ground pulp from approximately 70 per cent spruce and 
30 per cent balsam, ground at close to 70 horsepower with a 10-cut, screw-thread 
burr, at 160° F. The other pulp is of similar wood and similar grinding, except 
that it was stored for six months in a dark, high basement where it quickly 
became infected, as the laps show. 
The decayed pulp was found to be very free, brash, and brittle, 
and in some of the badly decaj^ed areas could be crumbled to a dust 
by rubbing between the fingers. The fiber length averaged 0.25 
millimeters, as compared with 1.09 millimeters for the freshly ground 
pulp. (See PI. XI, figs. 3 and 4.) Under as nearly identical beater 
and machine conditions as possible, both pulps, without the admix- 
ture of other fibers, were run into waterleaf paper on the laboratory 
machine. The decayed pulp ran much freer and also showed a tend- 
ency to stick to the couch and press rolls. It foamed badly, and 
this trouble was not overcome even with the addition of 2 per cent 
size and 2.5 per cent alum. Owing to the excessive amount of fine 
fiber, approximately 8.5 per cent more of the decayed than the sound 
pulp was lost in the white water. 
The paper made from the decayed pulp was considerably darker 
than that from the fresh pulp. The difference, evident to the eye, 
was also clearly indicated by color readings on the Ives tint photom- 
eter, which gave for the decayed pulp 50.5 per cent white and 39.5 
per cent black, and for the good pulp 60.5 per cent white and 23 per 
cent black. The paper from decayed pulp was much the dirtier, con- 
taining 20 times as many specks per unit area as the other. It pos- 
sessed less than half the bursting strength and only about half the 
tensile strength, and was only one-tenth as resistant to ink penetra- 
tion as the paper made from sound pulp. 
Tests were then made, under more carefully controlled condi- 
tions, (1) to check the results obtained on pulps from shipments A 
and B, and (2) to determine the relative resistance of pulps made 
from sound and from decayed wood to decay in storage. Pulps in 
the form of commercial laps were stored at the Forest Products 
Laboratory in a room in which were maintained a high relative 
humidity and a temperature suited to the development of fungi. 
A number of the laps were selected from pulps freshly ground from 
sound and from decayed spruce, data for which have been given in 
Table 2. They were designated as pulp No. 1AA, made from sound 
wood No. 1, and pulp No. 2AB, made from decayed wood No. 2546. 
Other laps were selected from a shipment of hydraulic-pressed pulp, 
No. 3 AC, received from a Wisconsin mill. This material was in 
reasonably sound condition at the time the tests began; otherwise 
its history is not known. All the pulps were stored in the humidity 
room for a period of 12 months. In the same room during this 
Eeriod were stored 4,000 small laps of mechanical pulp which had 
een sprayed with disinfectants and inoculated with various molds 
and wood-destroying fungi, and also a large amount of badly de- 
cayed hydraulic-pressed pulp as a source of infection for the three 
pulps under observation. There was ample opportunity, therefore, 
for these to become thoroughly infected, as they did, during the test 
period. 
