This study focused on solute diffusing into cell walls in solution-impregnated wood under conditioning, process of moderate drying of solvent. The purpose of this paper was clarification of the effect of evaporation rate of solvent on the solute diffusion in the impregnated wood. Wood samples impregnated with an aqueous solution of polyethylene glycol (PEG) were conditioned in an atmosphere with constant temperature, with equilibrium relative humidity (RH) of 32 or 75%, and with three types of convection. For both the RHs, the forced convection caused the highest evaporation rate of water, which was indicated by the mass of the sample, followed by the natural convection without and with mesh barriers. The total amount of PEG diffusing into cell walls, which was evaluated using the dimension of the sample dried in a vacuum after the conditioning, decreased and increased at RHs of 32 and 75%, respectively, with the increase in the evaporation rate. This amount at 75% was equal to or larger than that of 32%. For the efficient conditioning, it is preferable to condition the impregnated wood sample to the equilibrium moisture amount at which the ability of aqueous-PEG solution in the sample to swell wood is the highest, as soon as possible, and subsequently to dry it with slower evaporation rate.
