Superior tonewood has a low density and high Young‘s modulus of elasticity, say EMPA resarchers into whether the acoustic properties of Norway spruce and sycamore wood can be improved with a controlled degradation process.
Superior tonewood has a low density and high Young‘s modulus of elasticity, say EMPA resarchers into whether the acoustic properties of Norway spruce and sycamore wood can be improved with a controlled degradation process.

  The wood craft, finishing and lacquers used on the imitable 18th Century Stradivarius violins were long thought to be the key to their unrivaled sound.

Work on "tone wood" by researchers at the EMPA Swiss Federal Laboratories for Materials Science and Technology support another theory: the wood itself was milled from trees that had suffered through a sustain period of drought. As a result, the wood is less dense, and yields instruments that are more resonant.

Whether contemporary mills could treat wood to obtain the same effect was the goal of resarch by Prof. Dr. Francis Schwarze (francis.schwarze@empa.ch) and his team at EMPA. The current project, Mycowood, has found some success in using a fungus to improved acoustic properties of wood for violins. An abstract of the work says:

The quality of wood for the manufacture of music instruments (tone wood) is determined by its physical properties. Wood with a low density, high velocity of sound and modulus of elasticity has superior properties i.e. its resonance characteristics and sound radiation is improved.

The objective of our investigations is to improve the material quality of tone wood by exposing it to decay fungi under controlled conditions. The latter fungi differ from most other fungi, as they reduce density but do not degrade highly lignified cell wall regions resulting only in negligible changes in the velocity of sound. We are in the process of developing and optimizing the treatment methods for the modification of Norway spruce and maple wood and defining factors that are essential for the material quality: mass loss, velocity of sound, modulus of elasticity, eigenfrequencies and other physical properties. On the basis of a patented procedure, it is our long term objective to manufacture a prototype violin assembled with decayed wood [editor's note: this has been done and more are being made.]

While the subject is intriguing for luthiers of all stripes - guitars makers will find it interesting - it also has implications for controlling wood rot in a natural manner. The project springs from a Swiss national effort launched in 2008 to find new sustainable uses of the Swiss forest as a raw materials source, in a research initiative called "Wood Fibre 2020."

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