The objective of this study was to obtain the fundamental findings on impregnation of water-born wood preservatives into refractory wood species. Liquid impregnation into the three direction of wood specimens of five softwood species was investigated with permeation through capillary and penetration by pressure process. The liquid retention with pressure process was higher than that with permeation through capillary. The liquid retention in the radial direction for radiata pine (Pinus radiata) sapwood was the highest among those of the five species. In the case of capillary process, the net-retention of liquid for the other four species were larger in the radial direction than in the tangential direction. In the case of pressure process, on the other hand the net retention of liquid for these species were larger in the tangential direction than in the radial direction. The factors which would obstruct the penetration of liquid into wood was confirmed as follows.
1. The axial direction : the aspiration of the bordered pits.
2. The radial direction : permeability through cross-field pits and permeability between ray parenchyma cells.
3. The tangential direction : permeability in the bordered pits on the radial walls of tracheids.
Thus permeability of liquid into wood was much dependent upon the degree of obstruction by these factors and through subsidiary penetration through the three directions. There is not a large difference between the net liquid retention of AAC-based (mixture of AAC and polyalkylene glycol) and CCA preservatives with the pressure process, however, the former showed higher permeability than latter where the capillary process was applied. The AAC seems to be one of the effective water-born preservatives applicable to the refractory wood species, so that more practical studies on its permeable conditions should be conducted.

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