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Making Of

An instrument is created

Explanations of the individual steps are shown in the light box. Have fun!

Varnish? Filler!

It is no longer a secret that the varnish plays a much less important role in the sound of an instrument than is always claimed. On the other hand, the so-called filler, a layer between the wood and the varnish, deserves much more attention in this respect. It has the important task of preventing the varnish from penetrating the wood. In other words, it is supposed to fill the cellular interiors of the wood surface that have been exposed by the treatment and thus form the screed of the varnish, so to speak.

Oils and oil varnishes are not suitable as sole components because of their high creep capacity. They would penetrate deep into the lower cell layers via the pits in the cell walls (Figs. 3 and 5) and damage the sound of the wood after they have hardened. Predominantly water-based, but also alcohol-based preparations lack the ability to optically 'fire up' the wood to produce a deep light.

In 1989 a two-part article¹ appeared in Strad Magazine, publishing the results of an investigation of pore fillers on several fragments of old Italian instruments, including those of Strad violins. The examinations with the help of an electron microscope and EDAX² clearly showed that a mineral substance is an essential component of the filler. Its particular fine-grainedness and the astonishing uniformity of the grain size are striking.

This, I was convinced, could be the solution to the riddle. If, for example, one were to process an oil varnish with such a fine powder (grain size clearly below 10µm), one would obtain a paste (similar to a tube of paint) in which the creep of the binder would be largely eliminated and which could be easily applied to the wood surface. But how was it possible for the violin makers (or their suppliers?) of the time to achieve such a small and, above all, uniform grain size, and which mineral should I choose?

As we know, one quality feature of first-class old Italian varnishes and fillers is their transparency. So it had to be a mineral that becomes transparent in a binder due to a similar refractive index as glass. Volcanic glass - pumice! Vesuvius, Etna and the Lipari Islands are on the doorstep...

After a few attempts, I succeeded in achieving this fine and uniform grain size with a simple process. A procedure that the old masters could also have used: Grind the pumice as fine as possible and then slurry it in plenty of water. What does not settle as sediment at the bottom of the vessel after a certain time is poured off and left to stand until the water is completely clear. After the water has been poured off again, the sediment can be dried and rubbed together with the binder into a paste using a muller.

A lucky coincidence helped me some time later to check my samples under an electron microscope. Thanks Jörg! I would like to share some of the images with you here. Explanations are also shown here in the light box.

¹ 'Firm ground? Old ground layers under the microscope', Parts 1 & 2. C.Y. Barlow & J. Woodhouse. The Strad, March and April 1989
² Energy Dispersive Analysis by X-rays, an analytical method that provides information on the elemental composition of the sample.