Varnish not only protects a violin, it also influences the instrument's sound

March 8, 2016, Springer
The 'Caspar Hauser' violin by Giuseppe Guarneri 'del Gesu.' Credit: Walter Fischli - Stiftung / Martin Spiess

Varnish does more than just provide a protective sheen to a violin. It influences the vibrations and impulses that the wood absorbs and therefore the quality of sound the instrument produces, says Marjan Gilani of the Swiss Federal Laboratories for Material Science and Technology (EMPA) in Switzerland. In research published in Springer's journal Applied Physics A, Gilani and her colleagues demonstrate the importance of the vibro-mechanical properties of varnish, its chemical composition, thickness and penetration into wood.

Often, a violin's sound board is made of spruce tonewood. Varnish is applied to protect the from the long-term effects of humidity and wear. Violin makers normally have their own particular method for applying varnish to finished instruments. It is applied in liquid form, and then dries to a solid transparent film.

Gilani's team investigated how the hardening effect of varnish changes the vibrational properties of master grade tonewood specimens when using four different varnishes. The researchers prepared two simple varnish recipes themselves, and obtained two other varnishes from German master violin makers. These were applied on specimens of Norway spruce tonewood cut from the outer and inner part of the same tree.

Non-destructive methods such as vibration tests and X-ray tomography techniques were used to take measurements before and after coating with the various varnishes, and at different stages of hardening. The thickness of the varnish and the depth to which it penetrates into the wood were among the features measured. The researchers carefully noted how the microstructure and physical properties of each varnish influences the wood's natural frequencies and internal damping. The latter refers to a material's ability to absorb and stop vibrations quite rapidly.

It was found that all the varnishes increased damping throughout the wood surface. A moderate increase of damping can, in general, benefit the sound of violins. When high notes are dampened, instruments sound warmer and more mellow. In unvarnished wood, the sound is faster along the grain and slower perpendicular to it. The sound is also damped more strongly perpendicular to the grain than along the grain. With all applied varnishes, these differences are reduced, leading to a more isotropic sound radiation. The varnishes of the German violin makers reduced these differences even more than the laboratory varnishes. Additionally, their varnishes also allowed for a higher sound radiation than the laboratory varnishes, thus leading to a louder tone to be emitted.

"Varnish coating plays an important role for the long-term quality of the of wooden musical instruments, but as applied on the wood surface, impulse changes in the vibro-mechanical behaviour of wood can be recorded," says Gilani.

Explore further: Scientists unveil historical clues to Stradivari's craft

More information: Marjan Sedighi Gilani et al. Relationship of vibro-mechanical properties and microstructure of wood and varnish interface in string instruments, Applied Physics A (2016). DOI: 10.1007/s00339-016-9670-1

Related Stories

Scientists unveil historical clues to Stradivari's craft

July 8, 2013

A new study, by Marco Malagodi from the Università degli Studi di Pavia in Italy and colleagues, uses a range of analytical methods to identify the techniques used by violin master Antonio Stradivari in the 17th century, ...

Scientists reveal 'woodquakes'

July 17, 2015

The structural properties of brittle materials like rock or ceramic, such as cracking under stress, have long been studied in detail, providing insight into avalanches, earthquakes and landslides. Wood and its response to ...

On the road to creating an affordable master instrument

December 9, 2011

Violins made of wood treated with fungus need not hide their lights when compared to a Stradivarius, as a blind test has already demonstrated. However, these tonal masterpieces are only available as individually-made instruments. ...

Recommended for you

How heavy elements come about in the universe

March 19, 2019

Heavy elements are produced during stellar explosion or on the surfaces of neutron stars through the capture of hydrogen nuclei (protons). This occurs at extremely high temperatures, but at relatively low energies. An international ...

Trembling aspen leaves could save future Mars rovers

March 18, 2019

Researchers at the University of Warwick have been inspired by the unique movement of trembling aspen leaves, to devise an energy harvesting mechanism that could power weather sensors in hostile environments and could even ...

Quantum sensing method measures minuscule magnetic fields

March 15, 2019

A new way of measuring atomic-scale magnetic fields with great precision, not only up and down but sideways as well, has been developed by researchers at MIT. The new tool could be useful in applications as diverse as mapping ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.