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

Abstract

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.

Impregnation of Preservative and Fire Retardants into Japanese Cedar Lumber by Passive Impregnation

“…As reported by Ando et al (2012), minute surface cracking and slight darkening were observed when Japanese cedar specimens were dried by superheated steam after preservative impregnation. Surface cracking during drying is common for Japanese cedar lumber (Nakada et al 1998), and kiln drying of this lumber is a problem facing the Japanese wood industry (Obataya et al 2006).…”

“…4), as measured by color indicator method described by AWPA (AWPA 1993). Longitudinal penetration is common for the passive impregnation method, as reported by earlier works 2009a,b;Ando et al 2012;. Preservative penetration on the longitudinal/radial surfaces was also greater than 93% at any depth that was cut, and the outer surfaces that were 0 and 12 cm from the laser-irradiating surface had higher penetration than the inner surfaces, which were 3, 6, and 9 cm from the surface.…”

“…These results are also supported by previous works, in which the final drying condition considerably affects fixation and chemical leaching (Kartal et al 2009;Kang et al 2008;Humara et al 2006), although the results differ depending on experimental conditions. In earlier studies using the passive impregnation method, the leaching results were much lower than in this study, where only preservative was impregnated into the wood (Ando et al 2012;.…”

“…In this method, steam is injected into the lumber by a steam injection press through CO 2 laser-incised pinholes; the lumber is then dipped into a preservative. Effective preservation of all timber species with any moisture content can be achieved by this method 2009a,b;Ando et al 2012;Hattori et al 2005). This method is also very good with respect to cost (Islam et al 2008) and time (Ando et al 2012).…”

“…Effective preservation of all timber species with any moisture content can be achieved by this method 2009a,b;Ando et al 2012;Hattori et al 2005). This method is also very good with respect to cost (Islam et al 2008) and time (Ando et al 2012). However, for all previous studies, only preservative was impregnated into lumber by the passive impregnation method.…”