How Your Violin Varnish Affects the Tone of Your Instrument
Research recently published in a Springer’s journal ‘Applied Physics’ highlighted something that violin makers have known for some time – that the varnish on your violin can (along with several other factors) play an important part in shaping the tone of your violin. The research by Marjan Gilani of the Swiss Federal Laboratories for Material Science and Technology (EMPA) and her colleagues investigated how the hardening effect of varnish changes the vibrational properties of master grade tonewood. This wood was used in the research because a violin’s sound board is usually made of spruce tonewood. The researchers used 4 different varnishes in their study, 2 from German master violin makers and 2 simple varnishes that they had made themselves. To keep things as consistent as possible the 4 different varnishes were then applied to tonewood pieces that had all been cut from outer and inner parts of the same Norway spruce tree.
The researchers then carried out a number of non destructive tests on the different pieces of wood before and after the varnishes had been applied, and at different points during the hardening process. Vibration tests and X-ray tomography (X-ray images taken from different angles to produce cross-sectional images of different areas of the wood) were used. These methods allowed the researchers to measure:
- The thickness of the varnish
- How far the varnish penetrated into the wood
- How the structure and properties of the varnish affected the wood’s natural frequencies and internal ‘damping’ i.e. its ability to absorb vibrations quickly.
Where wood is unvarnished (apart from being unprotected) the sound moves more quickly along the grain, and moves more slowly across the grain. One of the main findings of this research was that all of the varnishes increased damping throughout the surface of the wood, and that differences in the way the sound radiated in different directions across the wood were reduced by the varnish. The researchers also found that the varnishes made by the German violin makers enabled higher sound radiation than the laboratory made varnishes thus enabling a louder tone. The German maker varnishes were also found to do a better job of giving a more uniform sound radiation across the wood.
One important function of the varnish on your violin is of course to provide a protective layer and an attractive appearance. This research shows that the ability of a good varnish to change the vibro-mechanical behaviour of wood means that varnish has another important function i.e. in shaping the tone of your instrument. A high quality violin varnish can help to give a warmer tone (especially to the higher notes) and can affect the long-term quality of the sound that your violin makes. The damping effect on the wood and the effect of creating a more uniform sound movement through the wood mean that a good varnish is an important component in improving the sound of an instrument. Applications of varnish e.g. in restoring a violin and / or replacing parts where varnish is worn is therefore a job best entrusted to specialist violin repairers / restorers.