Abstract
Wood is commonly used for making musical instruments. During the process it is often subjected to treatments, that either modify its volume or its surface properties. Two species used for for string instruments were studied, representative of different cultures: Spruce (Picea abies Karst.) used in Europe and White Mulberry (Morus alba L.) used in Iran. For each of them the effect of thermal treatment at moderate temperature (<150°C) and of coating on various physical and mechanical properties was studied. The main results are as follows. In contrast to Spruce, Morus has a very low degree of mechanical anisotropy. For both species, thermal treatment induces a strong decrease in damping, especially in R direction for Spruce, and equilibrium moisture content, without marked degradation as indicated by the very small weight loss. However, after reconditioning at high humidity, a significant part of the changes is recovered. The application of a solvent-based varnish on Morus induces a continuous stiffening, while a very strong increase in damping after application is followed, after about 2 months, by a return to values close to those of untreated wood. For Spruce, siccative oil based varnish was applied and several parameters of the process were tested. In this case, the kinetics of property stabilisation are very slow and significant changes were still observable after 5 months.