Abstract: A process for treating wood involving impregnation of the wood with a preservative followed by the heat-fixation of the preservative in the wood using a pre-heated aqueous heat transfer fluid to effect the heat fixation of the preservative. The process particularly relates to steps which are taken to reduce the level of any contamination of the aqueous heat transfer fluid resulting from any wood extractives, any unfixed preservative and/or any particulate matter (i.e. "sludge") that may be present in the fluid. The contamination is preferably reduced by incorporating in the heat transfer fluid an oxidant which will preferentially oxidize any wood extractives resulting from the contact of the treated wood with the fluid without any significant reaction occurring between the oxidant and the preservative. Useful oxidants include inorganic chlorate salts such as sodium chlorate.

Abstract: An improved process for the fixation of preservatives in wood is disclosed which initiates the fixation process in the fixation vessel by the application of sufficient pressure to substantially obviate a thermal expansion effect of the treated wood; contacts the treated wood in the fixation vessel with an aqueous liquid heating medium preheated to a temperature of about 130.degree. to no more than about 200.degree. F. for a period of thirty minutes to about two hours; removes the aqueous liquid heating medium from the fixation vessel; applies a vacuum in the range of 10-30" Hg for a duration of up to about 30 minutes; and rinses the treated and fixed wood in said fixation vessel with heated clean water, heated to a temperature of about 200.degree. F.