High-quality tone wood through treatment with fungi

Researchers at EMPA, above all Prof. Dr. Francis Schwarze, want to prove that modern violins made of bio-tech wood can compete with masterpieces by Giuseppe Guarneri. The Italian violin maker’s exemplar are among the most sought-after and expensive in the world. A few years ago, one of his violins was sold for 18 million dollars!

Guarneri benefited from the wood that grew during the climate in the 18th century. A short ice age at that time caused long and hard winters. These extreme conditions led the trees to form thinner-walled wood cells. The result was wood with a low density, which meant that the sound was conducted very well.

Materials researcher Prof. Dr. Francis Schwarze developed what is known as MycoWood in the laboratory. Together with his team from the Swiss Federal Laboratories for Materials Testing and Research – Empa – in St. Gallen, he treated wood with special fungi. The wood was colonised with the pathogen of a white rot – Physisporinus vitreus – which normally occurs as a pest on trickle disks in cooling towers. This fungus became a beneficial organism in the Empa laboratory under controlled conditions, reducing the density of the wood and thus optimising the sound properties. As soon as the perfect density of the wood is reached by the wood decomposition, the wood is sterilized with a killing gas. (Ethylene oxide cannot remove the fungus.)

The Empa violin project is generously supported by the Foundation of Walter Fischli, a biochemist and honorary doctor of the University of Basel. The aim is to make high-quality violins available to young talents. These will then sound similar to the masterpieces from the 18th century, but are affordable. Not only star musicians but also young talents could then play on such instruments.

Until then, conscientious tests will be carried out in the Empa acoustics laboratory in Dübendorf. Scientist Dr. Armin Zemp and his team are investigating whether violins made of bio-tech wood can sound as warm and round as antique instruments.

Foto: Jorma Müller

The tests are carried out with a total of four violins. One of them is a masterpiece by Guarneri (1698-1744). The other three violins are replicas and were made entirely or partly of wood by Swiss and French violin makers, which was treated with the pathogen of white rot Physisporinus vitreus. The original violins and their replicas have been copied down to the smallest detail. Even the scratches and traces of use in the wood are indistinguishable.

Only Dr. Zemp knows which violin is the antique treasure and which is a copy. However, the employees are not informed about the correct assignment. This should help with the objectivity of the assessment in the tests.

A whole year now takes up the systematically measurement of sound by means of sound velocity, sound attenuation and density. Ultrasonic experts develop methods to prove in which areas the rot fungus was active and where not. Professionals in optical measurement techniques use methods that can be used to image how different tone woods and even entire instruments emit acoustically.

For another year, the Empa team will work together with test persons from the relevant psychoacoustic expert groups to understand how violinists and listeners perceive and experience the music of a fungi violin. If the fungi violin passes the tests with flying colours, nothing will stand in the way of a musical future for MycoWood.