EFFECT OF KILN DRYING, ETC., ON FUNGI IN WOOD. 17 
REVIEW OF THE RESULTS. 
Sterilization by heat is a well-known process and has its examples 
in many everyday activities. The canning of fruit is probably the 
best-known example, and it is but a short step from this to the 
sterilization of wood—a very similar process. The protection of 
wood against future infection is not accomplished by sterilization 
alone. Proper care following sterilization is absolutely essential, and 
in the case of lumber proper storage to insure dryness is the process 
by which reinfection is prevented. This fact has prompted the in- 
clusion of the air-seasoning data for correlation with the results of 
the heat experiments. It will be of interest to note here that wood 
when properly kiln dried is equal in strength to air-dried wood when 
moisture contents are carefully considered (/0). 
A brief consideration of the factors affecting the penetration of 
heat. into sound and infected wood may not be out of place here. 
Very little has been published on this subject. Hunt (3) in a series 
of experiments obtained data on the rate of heat penetration into 
sound wood of various sizes and species. Using sawed ties of maple, 
red oak, loblolly pine, and hemlock 6 by 8 inches by 84 feet he found 
that under the conditions of the experiments no appreciable dif- 
ference in rate of increase of temperature due to difference in species 
could be determined. He also observed that the interior of the ties 
never quite gained the temperature of the heating medium and that 
seasoned ties heated more rapidly than green ties. In the treatment 
with steam at 20 pounds pressure the time required for the interior 
to reach 212° F. varied from 2? to 5 hours, averaging 4 hours and 
20 minutes. With steam treatment at atmospheric pressure the ulti- 
mate maximum temperatures within the ties varied from 2 to 17 
degrees IF. Jess than the temperatures of the surrounding medium. 
With steam at 20 pounds pressure the variation was from 2 to 21 
degrees F. 
In regard to the experimental data in this bulletin, the effect of 
heat upon the fungi in the wood was observed to vary with the size 
of test pieces and ‘the relative porosity of the wood as expressed by 
the stage of decay. In many cases negative cultures were obtained 
from portions of the culture block, showing a typical stage of decay 
which was obviously more porous than the near-by areas of 3 incipient 
decay. In other cases the blue-stain fungus present in the sapwood 
of the piece was killed in blocks showing a brown cubical or brown 
ring-rot in the adjoining heartwood, and it remained alive in blocks 
of similar size containing only incipient stages of decay in the 
adjoining heartwood. The data on the steaming experiments when 
plotted on coordinate paper show in general a definite relationship 
between time and temperature. This is clearly evident in the curves 
shown in Figure 1. Curve A is drawn through points representing 
data on the 1-inch test pieces. Curve B is more or less theoretical 
and represents roughly the time and temperature limits necessary 
to kill certain fungi in wood up to and including 4 inches in thick- 
ness. The point in Figure 2 showing death of the fungi in 4-inch 
stock subjected to 140° F. for six hours is considerably “outside the 
curve and theoretically should coincide with the curve near the 43- 
hour point. It is evident that the fungi in this case were killed 
