Abstract: A method of removing liquid solvent from wood after pressure treatment with a preservative solution evaporates the excess solvent by mechanically circulating heated vapor of the same solvent used in the preservative solution past the wood in an autoclave. The autoclave is maintained at a constant pressure by transferring evaporated solvent to a condenser at a rate equal to the evaporation rate of solvent from the wood in the autoclave. The heat extracted from the condensing solvent vapor provides the heat to the circulating vapor in the autoclave for evaporating additional liquid solvent from the treated wood. Preferably, the vapor transferred from the autoclave is compressed before its delivery to the condenser so that the heat needed for evaporation in the autoclave can be obtained by simple heat transfer of the excess heat from the condenser.