Permeable wood species for use in preservative-treated commodities are becoming depleted in Canada. Spruce can be a convenient replacement for them from local resources provided it can be treated to levels adequate for protection of commodities in ground contact. Basically, two approaches were taken to improve treatability of difficult-to-penetrate softwood species; first, to improve the permeability of wood and second, to improve the penetrating properties of liquids. The first approach involves various means of wood pre-treatment: biological (enzymes, moulds and bacteria including ponding), chemical (removal of extractives), mechanical (precompression) and technological (presteaming of green wood, replacement of water in wood by solvents). There are a great many publications devoted to individual topics mentioned here indicating the significance of the subject. The second approach is the selection of a solvent capable of penetrating into the wood better than conventional solvents for, preservative compounds.

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