Varnish Effects on Plates Options

[Michael_Molnar]

Can anyone point me to studies on the effects of varnish on the eigenmode plate frequencies?

Along similar lines, can anyone site the effects of varnish on the air and body modes of a violin?

Mike

[Adam Edwards]

hi Mike , Carleen Hutchins did write about this ....I think she compensated for change in mode 2 ( from memory )
my own personal opinion is that the effect is greater on the harmonics than the fundamental modes
great topic !!

[Anders Buen]

Can anyone point me to studies on the effects of varnish on the eigenmode plate frequencies?

Along similar lines, can anyone site the effects of varnish on the air and body modes of a violin?

Mike

Hutchins has reported on the effect of varnishing on plates. It might have been in her 1982 (?) Scientific American article.

Varnish effect on assembled instruments has been reported by Meinel and Schelske.

Meinel: "Regarding the Sound Quality of Violins and a Scientific Basis for Violin Construction" J. Acoust. Soc Amer 29, 817-822 (1957) reprinted in Benchmark Papers in Acoustics v 5 "Musical Acoustics, Part 1" Ed by C M Hutchins, Dowden Hutchinson and Ross Inc, I think in 1973.

Schleske: In one of his 2002 articles in the CASJ.

[Anders Buen]

Can anyone point me to studies on the effects of varnish on the eigenmode plate frequencies?

Along similar lines, can anyone site the effects of varnish on the air and body modes of a violin?

Mike

Hi again,

I have to correct my former post. Scheskes figure of admittance in a white versus a varnsiedhed violin is shown in his Nov 1998 CASJ article "On the Acoustical Properties of Violin Varnsih".

I also found an other classic article on the subject by Schelleng "Acoustical effects of Violin Varnish" again from JASA, vol 44, no 5 pp 1175-1183, 1968 reprinted in Research Papers in Violin Acoustics 1875-1993 edited by Hutchins and Benade.

All these measurements are done on bodies that are not held for playing, or just held by a hand.

[Don Noon]

I knew "Flash Drive Buen" would find the data before I could get around to sifting through the SCAVM library.

[Michael_Molnar]

I have the Catgut Journal Index and will run through that and examine the articles "Flash Drive Buen" pointed out. Thanks to all

Stay Tuned.
Mike

[Anders Buen]

I may not be a good source on the subject because my working methodes is so that I add the varnsih before I start to monitor the modes of the plates. The thciknesses will also be unaturally thick prior to varnishing.

In my master thesis work I monitored the modes in some violins and a white hardanger with rather thick plates (as usual prior to varnish for me) + two unconventionally built violins. The Q values of the modes was recorded by a rather cumbersome manual process, but they are given in Figure 8 in this article for the modes seen from the top plate side. http://home.online.no/~an-buen/Buen_article_smac03.pdf

If you compare the diamond shaped values with those from the varnished fiddles you see that there is not really much of a difference. But here the fiddles rested on a cushion of rubber foam (stood upright on that foam) and against a rubber grip in the neck, se illustration in the article. I think that mounting may have added some damping to the modes. Using optic methodes like TV-holography requires the object to stand at rest. Suspension in rubber bands would have been impossible because the fiddles would move too much.. (With system using a pulsed laser you can hold the object in your hand and the stability is not so important. The stroboscope effect makes the object be enough at rest. We used a continuous laser).

I am now doing modal analysis using George Stoppanis software which does mode fitting as a part of the procedure. Then the damping factors come out as one of the fitted parameters in a table. So its easier to do this kind of analysis now. I have just started doing this and only on varnisned instruments this far.

George Bissinger has written articles on damping too. My stand is that varnish and sealer does damp the fiddle a little, but as long as the sealer and varnish is dry and the thickness not excessive, the effect will be small on the tone. Holding for playing will have a comparatively larger effect.

I think the moisture content of the wood may play a role for damping and that much used instruments may be more damped than drier ones. Moisture from sweat and breath adding to that effect. Microcracks may also have a damping effect, and may even be nonlinear so that the effect is small at low levels, but much stronger at higher levels. But much of this is speculation.

I have heard at least one maker say that he had stripped a fiddle due to data he got from a modal analysis. I think he had changed his varnish system. But again, the modal analysis is usually done with the fiddle hanging in rubber bands with small loss effects comapred to what you get holding it for playing..

[Anders Buen]

Just found the Meinel figure of a violin response with and without varnish. I do have a figure where I have changed his response to a dB scale, but haven't found it yet.

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[Anders Buen]

Here is Schleskes accelereance figure from his 1998 CASJ article on acoustical effects of varnish. The varnish used is oil based, similar to this:

Primer: Sandarc in oil of lavender - according to Bonnani (Rome 1713)
Varnish: mastic, dammar and melted copal with a little linseed oil added to the turpentine oil, in use in the Geigenbaushule, Mittenwald

14 days drying period including 80h in an UV box.

[Edited]

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[Anders Buen]

Carleen Hutchins participated on the 1983 Stockholm Musical Acoustics Meeting giving a talk named: "What the Violin Maker Wants to Know". She addresses the effect varnish has on the plates as given in the following two attachments. Not measured data, but a practical approach to the issue giving an idea of the effect.

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