"THE SURFACE ENERGY OF COATING LAYERS USED FOR VIOLINS VARNISHING "

Numerous studies on new and historical violins have highlighted the importance of coatings for the acoustics of the musical instrument. The purpose of this paper is to present the results regarding the surface energy of resonant wood, spruce and maple in two states: lacquered and unvarnished. The method is based on static contact angle measurements of sessile drops. The obtained results highlight large differences in surface energy depending on the wood section (radial versus longitudinal), surface (lacquered versus unvarnished), wood species. Thus, although the surfaces are polar for both unpainted and lacquered samples, it can be seen that there is a tendency to increase the contact angle after applying the surface treatment (applying the varnish). In the case of spruce wood cut in the longitudinal direction, the contact angle increases by about 31% in the case of the lacquered surface. For maple wood, the increase is 10%. For radially cut spruce wood samples, it is observed that the contact angle is higher than 90°, the surface having a hydrophobic character, a characteristic that is not found in maple wood. The application of the varnish on the radial surface diminishes the hydrophobic characteristics of the spruce wood. In maple wood, the difference between the longitudinal and radial samples is very small (2%).