In the processes of drying, preservation and chemical treatment of wood, the permeability is of importance. Generally the heartwood of softwood has poor permeability because of aspirated bordered pit-pair. An attempt is now being made to develop the local steam explosion method to improve it. In this study, the improvement of dryability and its distribution by the local steam explosion was examined. A repeat of explosion and heating methods were investigated as the factors which affect the drying distribution. The results obtained were as follows;
(1) The local steam explosion was better than the steaming for the improvement of drying rate.
(2) The improvement of dryability by the explosion was affected by the repeat of explosion. In case of a heating method by steam and radio frequency, the improvement of dryability progressed from the cross section to the central part of timber because temperature in timber was approximately uniform.
(3) In case of a heating method by steam only, there was a large distribution in temperature and the appearance of the effect of explosion corresponded to it.
