Résumé
Combinations of boric acid as a first step of treatment and linseed oil as a second step have been performed in order to enhance boron retention to leaching and wood resistance to termites. Classic leaching and termites resistance standards are inappropriate to evaluate this combination which can be considered as both a wood core preservation treatment and a coating. Japanese Industrial Standard (JIS K1571, 2004) on Japanese cedar (Cryptomeria japonica) Japanese beech (Fagus crenata) exposed to subterranean termite Coptotermes formosanus, and, European standards EN84 and EN117 on Pine (Pinus sylvestris) exposed to termite Reticulitermes santonensis have been performed for the same boric acid/ linseed oil treatments. Addition of oil as a water repellent to boron treated wood gave promising results with about 30% of initial boron retained. Termite mortality rates and efficiency thresholds using the different standards are determined and compared. Moreover, the relevance of Japanese mass loss indicator and European visual evaluation are discussed in the case of unconventional wood protection system such as boron/linseed oil combination.