2 BULLETIN 1262, U. S. DEPARTMENT OF AGRICULTURE, 
heat is introduced as a preliminary steaming or during impregnation, 
or both. 
The application of heat as a method of sterilization has a wide field. 
In most of the kiln-drying and steaming processes now in use where 
sufficiently high temperatures are used it serves the double purpose 
of seasoning and sterilizing the wood. However, in many of the 
steaming processes used primarily for the aed toy of softening the 
wood little or no attention is paid to the sterilization of the stock. 
Adjustments in temperatures and periods of heating may not only 
result in the killing of such fungi present in the wood before treat- 
ment but may prove beneficial in rapidly drying the surface of the 
wood during subsequent air seasoning and thus aid in the prevention 
of sap stains, molds, and decay. The slack cooperage industry 
presents among others one notable case for experimentation along. 
these lines. 
In the preservative treatment of wood where heat is used during 
the process the sterilization of the inner portions of the wood not 
penetrated by the preservative is often desirable. Very often ties, 
posts, poles, and timbers of various kinds contain before treatment 
certain active decay organisms which are fully capable of reviving 
under favorable conditions, continuing the decay process, and even- 
tually weakening the wood. Sterilization would not only greatly 
reduce the chances of loss from such a source, but would make it 
possible to utilize for less exacting purposes material containing to 
a limited extent certain types of incipient decay. 
In this connection it is necessary to take into account several fac- 
tors, among which the efficiency of the preservative, the relative ab- 
sorptivity, and the strength qualities of the infected wood are 
paramount. 
In the control of blue stain in lumber the use of chemical dips can 
at best protect only the surfaces of the wood against the stain 
organisms. In case the fungus is already present in the log before 
it is sawed into boards the dip solution has no effect upon the fungus 
within the board. Heat treatment in conjunction with the chemical 
action therefore would greatly increase the protection against blue 
stain. 
Steaming is the common method of applying heat in most of the 
commercial operations connected with the production and manu- 
facture of wood. although electricity may be used effectively in some 
eases. Directing an electric current through wood has been tested 
in this country, in France, and in Australia as a rapid method of 
seasoning,” and it is conceivable that the electric current may be used 
to advantage in the.sterilization of wood, particularly as a means 
of checking incipient decay of structural timbers in buildings, ships, 
bridges, or other structural units where it may be found impracticable 
to apply other means of heating. 
PREVIOUS WORK. 
Both Hoxie (2)* and Snell (8, 9) have contributed to the subject 
of the effect of heat on fungi in wood. Hoxie tried the experi- 
2Menzel, C. A. Preliminary experiment in the drying of wood by passing an electric 
current through it. U.S. Dept. Agr., Forest Serv., Forest Products Lab. Unpublished 
manuscript. 1921. 
* The serial numbers (italic) in parentheses refer to “ Literature cited,” at the end of 
this bulletin. 
