Lumber Treatment By the Vacuum Process

Vacuum process of treating wood with preservatives involves: 1) An initial vacuum to remove air from the cells of wood with either simultaneous or subsequent filling of the chamber with the preservatives with the vacuum on, 2) release of the vacuum and soaking to force preservatives into submerged wood under atmospheric conditions, 3) draining of the chamber and application of final vacuum to recover excess preservatives. Vacuum process for treating lumber can be applied to water-repellent preservatives, pentachlorophenol in heavy petroleum solvent, and water-borne solutions. Timbers smaller than 4 inches in thickness can be treated by the process to produce retentions ranges from 1 lb./cu.ft. to over 16 lbs./cu.ft. for dry southern yellow pine and from 1 to 9.6 lbs./cu.ft. for incised Douglas-fir. By the control of vacuum and time factors of a cycle, net retention can be controlled to within 2 or 3 percent. Specification for treatment of wood for use in buildings is presented.

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