2020 Volume 59 Issue 1 Pages 196-199
In Japanese traditional exterior wood constructions, such as temples, timber bridges, castles and old folk houses, copper based metal fittings are used to cover the edge of wood members. The fitting is considered to protect wood from the rain waters and decay. However, bio–deterioration of wood was inhibited also widely around the fittings in many cases. It is supposed that copper ion might be eluted from the fitting to the neighbored wood and inhibited decay. In the recent field analytical work on the traditional bridge, which has the bronze fittings, copper was detected in high concentration from the wood around fittings, and in the laboratory wood decay tests, copper plates suppressed the wood decomposition by decay fungi. These results support the possibility of copper and copper based metal as items to improve the durability of wood constructions. In this study, to understand the basic antifungal properties of the copper ion, the minimum inhibition concentrations (MIC) of water soluble copper salts, such as CuSO4, Cu(NO3)2, Cu(CH3COOH)2 and CuCl2, against wood decay fungi, Fomitopsis palustris, Trametes versicolor, were determined by a broth dilution method. The MIC of metal salts containing Zn, Ni, K and Na, were also determined. The MIC of salts were converted to MIC of metals and anions, and compared with one another. As a result, MIC of each metals were consistent and were not affected by the kind of the anions. It is confirmed that antifungal effect of the soluble metal salts, such as copper salts, is dependent on the concentration of metal ions and not affected by the anions.
