Effect of steam injection re-drying of Japanese cedar on preservative leaching after passive impregnation

This study investigated the effects of steam injection re-drying on the leaching of copper azole type B (CAz-B) preservative from green and kiln dried Japanese cedar (Cryptomeria japonica (L.f.) D. Don) lumber treated by the passive impregnation method. The leaching and fungal treatments were performed according to the JIS Z 2101-1994 standard. Sixteen hours of steam injection re-drying reduced the moisture content from 152 to 82% and 195 to 55% for initially green and dry lumber, respectively. Preservative retention was higher in the dry lumber (5.21 kg/m(3)) compared with the green (4.66 kg/m(3)), however, leaching percent was similar for both types. Preservative leaching and mass loss due to fungal attack were significantly lower in the lumber re-dried by steam injection compared with air dried. Thus, steam injection re-drying after passive impregnation treatment could be a step toward fixing CAz-B preservative in Japanese cedar lumber.