Varnish influences the sound of violins
Varnishes protect works of art and wooden instruments from damage caused by environmental influences. Until recently, however, little research had been carried out into how varnish affects the sound of violins. Empa researchers have now investigated this connection and published their initial results.
Marjan Gilani from Empa's "Applied Wood Research" department and other employees, including Geige builder Johanna Pflaum, examined twenty wood samples for their sound behavior and coated them with selected varnishes. The same varnish was applied to five of the twenty wood blanks per sample type and dried and cured for eleven hours using UV light.
In longitudinal samples, the varnishes increased the sound insulation of the heartwood and the young wood and reduced their stiffness compared to the raw state. This may be desirable: The more elastic the wood of a violin is, the warmer and softer the high notes sound. However, this change is accompanied by a loss of clarity and sharpness in the violin sounds. The situation was different for cross-rehearsals. For these, both the sound attenuation and the stiffness increased. The values for sound propagation also increased.
In general, a correlation emerged between the varnish composition, the microstructure of the wood-varnish composites, their mechanical properties and their sound behavior. Gilani and her research group want to refine these findings in further studies. To this end, another scientist will join the research team from April 2016.
For comparison purposes, the Empa group also analyzed two antique violins (from Cremona and Saxony) at the Center for X-ray Analysis. The violin from Saxony showed extremely fine cracks in the varnish as well as surface impacts and suffered from woodworm infestation. Compared to this violin, the violin from Cremona had a higher density of the wood-varnish composite. As the density increases, so does the stiffness and the sound propagation values - the Cremonese violin will therefore have produced clearer tones than the violin from Saxony.
More info: www.empa.ch/web/s604/varnish-and-violins
