The sorption of preservative into wood during soaking in aqueous solution was found to comprise absorption as well as diffusion of solute. Absorption was increased by partially seasoning the wood prior to soaking and was characterised by (a) a very rapid initial rate of uptake and (b) an extended period of slow uptake, the rate of which varied with prior conditioning. It was concluded that some partial seasoning was desirable to optimise absorption (and therefore reduce soaking times), but that extensive partial seasoning would not significantly increase the quantity of solution taken up during short soaking periods, because of the back pressure from air which tended to become embellished in the wood during soaking. The factors influencing the retention of solute following momentary immersion were identified and included: 1. Surface roughness (which may be influenced by the basic density of the wood species together with the wood sawing or machining processes used); 2. The critical surface tension of the wood substrate; 3. The solubility of the solute; 4. The surface tension of the solution. It was found that during momentary immersion the surfaces of the wood become saturated very quickly. When stored overnight under non-drying conditions however, there was movement of the solution from the surface to the coarse capillary structure of the wood. Subsequent dipping in solution resaturated the surface of the wood. Thus by a process of multiple dipping preservative retentions could be increased as though timber had been kept in the solution.

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