Danube Fiddler

The importance of varnish

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On MN - discussions acoustical properties of varnishes seem not to play a big role. Rather more things like production, cooking, application and coloration. Often was told, that varnish can´t be the reason for fine sound in old-italian instruments, because these instruments mostly don´t have any longer enough (original) varnish. In contributions to the varnish- topic most makers seem to prefer a ground with quite opposite features than these, which are preferred in the varnish itself : ground - so hard as possible // varnish - quite soft. 

Now I have these questions

1) Which is the reason, why again and again makers warn, that a revarnishing could alterate the sound   but   nearly never talk on MN about a considerable influence of varnish on tone ? What is true in your experience : little or high influence ?

2) Why a ground has to be so hard ( e.g. mineral fillers, casein ) , while nearly nobody wants a hard varnish ? 

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Great questions Danube, i would also very much like to know.

For 1) i assume the sound will mainly be affected by just adding thick coats of oil varnish. Replacing varnish should not affect the sound if done right, but it could ruin the potentially historic value.

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4 minutes ago, Emilg said:

Great questions Danube, i would also very much like to know.

For 1) i assume the sound will mainly be affected by just adding thick coats of oil varnish. Replacing varnish should not affect the sound if done right, but it could ruin the potentially historic value.

Hi Emilg,

yes -  too thick oil-varnish coats could touch tone issues by adding to much damping. However I could imagine, that too thick coats of (hard) spirit varnishes wouldn´t be better. 

Naturally an instrument of historical value must not get revarnished. The idea came from another current thread about a 800 $ fiddle, where David Burgess warned and he was not the first.

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From my experience everything depends on the thickness of the top. When the weight and stiffness comes down to the limit the stiffening effect of the varnish can play a major role in the overtone production of the instrument. Tried and tested. 

 

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31 minutes ago, Danube Fiddler said:

...

The idea came from another current thread about a 800 $ fiddle, where David Burgess warned and he was not the first.

Link, please?

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1 hour ago, Andreas Preuss said:

From my experience everything depends on the thickness of the top. When the weight and stiffness comes down to the limit the stiffening effect of the varnish can play a major role in the overtone production of the instrument. Tried and tested. 

 

This is interesting.

Of which kind of limit you are speaking : lower or upper (stiffness)limit ?    In your idea soft ( often oil ) varnishes should be lesser influencing/alterating than hard (spirit) varnishes, which could give a lot of additional stiffness. 

If it should actually and mainly be a thing of stiffness, one would have to consider, that varnish particularly influences the cross-grain stiffness of the top. Topic of measuring could be the M2-mode in combination with weight, which should increase considerably by varnish.

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Adding a few coats of eggwhite on the inside of a top did add 10-15Hz to the M5, that's quite a bit i think. Same thing seems to be true for the varnish and ground. It would be interesting to measure M5 of a top with the ground coat and then every layer of varnish, but only measure after the layer has fully dried/hardened. I suspect after more than a few layers you are increasing the weight more than the stiffness, so the modes will go down again.

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Following the experience and idea of Andreas I can imagine 3 cases :

1)   top-stiffness ( absolute or relative to back stiffness ) is quite near the upper limit ( strong/dense wood and/or thick graduations )

     --> the additional stiffness of varnish can bring it out of the green area ( top to rigid ) --> bad sound 

2) top-stiffness is well within a normal-stiffness-zone, even within the lower areas of such a zone

-----> additional stiffness of varnish will not bring the top out of the green zone, the varnish will alterate character of sound but quality should remain on an acceptable level  ( " varnish doesn´t matter much" )

3) top-stiffness is too low ( weak, low-density wood and/or too thin graduations, eventually also bad split )

---> additional stiffness of varnish, may be particularly of a hard varnish could bring the top back into the green zone of sufficient stiffness  ( varnish even improves the sound-quality )

Providing, that varnish sound-effects are mostly coming from stiffness issues, particularly " strong building makers" ( favouring thick and resistant tops ) should be anxious about varnish effects ?

 

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3 hours ago, Danube Fiddler said:

Often was told, that varnish can´t be the reason for fine sound in old-italian instruments, because these instruments mostly don´t have any longer enough (original) varnish.

Varnish CAN be a contributing factor in the sound of old Italian instruments in that there isn't much varnish on them.  

In my testing, coatings aren't very good at "improving" the acoustic properties of wood such as stiffness/weight and damping.  Sure, coatings can raise some frequencies... but I think if you could have added that extra weight in wood instead of varnish, you'd see even more change to the stiffness and no increase in damping.

The sound of an unvarnished violin is usually pretty obvious, and to my ear too harsh and wild (perhaps less so if you use dead-ish wood).  A little bit of damping to smooth things out I think is a good thing, but a full coat of oil varnish might be too much.  Coatings without oil, such as water soluble or resin/solvent generally are lower damping, and could help minimizing the effect.  And keeping the coating as thin and light as possible is obviously in keeping with the same theme.

People here tend to look at frequencies, which are easy  to measure, but I think the main factor is damping, which is extremely difficult to measure.

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Random observations...

From the posts I have seen, experienced makers tend to claim that varnish can change the sound of a violin. But they do not generally claim that the change is good or bad. My take is that they spent considerable time to find a varnish and method that looks good, wears well, and can be applied consistently so that it becomes a "constant" of their making process as opposed to a "variable". They then look elsewhere to adjust the tone of their violins because they can trust that the varnish will have the "same" effect on each new violin. This seems like a good approach because varnish can have a bewildering number of affects on the violin...

Varnish adds mass to the violin. That means it will influence the response spectra of the vibrating system, and therefore the tone. How much it affects it depends on how much mass it adds to the violin relative to the mass of the wood. A thick top would be less affected by varnish than a thin top, assuming the total mass of varnish applied is the same between the two violins.

Varnish adds stiffness to a violin. That means it will influence the response spectra of the vibrating system. Again, this is relative to the existing stiffness of the wood. But is also depends on the makeup of the varnish. A pure linseed oil varnish would add little stiffness, but potentially lots of mass. An oil varnish with a high percentage of hard resin could add considerably more stiffness. Spirit varnishes can be very stiff.

Varnishes may or may not add damping to the system. Again, it depends on the makeup of the varnish and how much you apply to the violin. Increased damping can cause shifts in the location of the peaks of the response spectra, and it will also spread out and lower the peaks so that the response becomes more even across notes, but also more subdued.

 

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52 minutes ago, Don Noon said:

Varnish CAN be a contributing factor in the sound of old Italian instruments in that there isn't much varnish on them.  

May be - in this case one generally would have to aim for a varnish so thin as possible, as some makers try to do so. However providing this idea, we could ask : which are the detrimental effects of varnish in general, which must be limited ?

You have made opposite experiences : the varnish reduced harshness and "wildness" - positive effects. Did you ever examine, if these positive effects could be reached by ground only ?

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This might be also the right time to involve Hargrave's anecdote about his PoP ground. He suggested that the mineral ground hugely improved the projection of his violins.

Maybe this is not just caused by the ground or the varnish itself, but rather the fact that a physical barrier (ground) prevents the varnish penetrating the wood.  I'm just repeating ideas i came across reading the entire Pegbox :)

Any thoughts?

 

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17 minutes ago, Emilg said:

This might be also the right time to involve Hargrave's anecdote about his PoP ground. He suggested that the mineral ground hugely improved the projection of his violins.

Maybe this is not just caused by the ground or the varnish itself, but rather the fact that a physical barrier (ground) prevents the varnish penetrating the wood.  I'm just repeating ideas i came across reading the entire Pegbox :)

Any thoughts?

 

In this PoP ground were also involved some more components like oil or oil-varnish ? 

About the depths of varnish- or ground penetration within the Guadagnini Parma Exhibition book is to read, that in some places there is to see a penetration on the inner rib-sides. That would mean a penetration of until nearly  50% of plate-thicknesses of backs ( figured maple). May be these only have been little accidents in an otherwise well-working system, which apparently also involved particulates.

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The Plaster of Paris ground is just a gypsum in water slurry. When applied the whole violin becomes white, but this disappears when you add the varnish on top.

Here is an elektron micrograph of a Strad cello with a mineral ground: http://www.rubioviolins.com/Pages/ground1.html

Granted, you need a bit of imagination to see the separate layers, but i guess they know what they were talking about :)

The question to the Guad example would be: how did it sound? Of course this also applies to any finding on Strads.  I feel that the top is more important for sound production, especially the higher notes and harmonics.

Edited by Emilg
oopsie spelling error

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2 hours ago, Emilg said:

The Plaster of Paris ground is just a gypsum in water slurry. When applied the whore violin becomes white, but this disappears when you add the varnish on top.

Here is an elektron micrograph of a Strad cello with a mineral ground: http://www.rubioviolins.com/Pages/ground1.html

Granted, you need a bit of imagination to see the separate layers, but i guess they know what they were talking about :)

The question to the Guad example would be: how did it sound? Of course this also applies to any finding on Strads.  I feel that the top is more important for sound production, especially the higher notes and harmonics.

The info from Roger and also some research

- the complete ground/varnish - system apparently matters in sound concerns 

- Roger only tells about some advance in his ground-system ( PoP or similar things, later used ) with importance for sound. So far as I know, there are no comparable reports about the surface-building layers ("varnish" ).

- I would like to speculate, if the PoP-ground finally is not a dense one, rather more a micro-porous one. So there could sink in some amount of later applied oil or oil-varnish and resulting in a composition having both, some rigidity from gypsum but also some (wanted) limited damping by oil or oil-varnish.

The info from Guad i.m.o. is, that there was a quite penetrating thing in his varnish or ground - but normally on most places was prevented from too much sinking in by another ingredient or an applying trick. Brandmeir writes, that he used particulates ( = mineral ground ).

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4 hours ago, Emilg said:

Here is an elektron micrograph of a Strad cello with a mineral ground: http://www.rubioviolins.com/Pages/ground1.html

Granted, you need a bit of imagination to see the separate layers, but i guess they know what they were talking about :)

Possibly not so - At least, according to other researchers...

Re effects of varnish, Martin Schleske's article "On the Acoustical Properties of Violin Varnish" may be of interest to some.  See here:  https://stacks.stanford.edu/file/druid:yx381kq5616/CAS_yx381kq5616.pdf

Edited by John Harte
Material added

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10 hours ago, Danube Fiddler said:

This is interesting.

Of which kind of limit you are speaking : lower or upper (stiffness)limit ?    In your idea soft ( often oil ) varnishes should be lesser influencing/alterating than hard (spirit) varnishes, which could give a lot of additional stiffness. 

If it should actually and mainly be a thing of stiffness, one would have to consider, that varnish particularly influences the cross-grain stiffness of the top. Topic of measuring could be the M2-mode in combination with weight, which should increase considerably by varnish.

The thing is: how much you can drive the weight stiffness relation to the edge is extremely difficult to measure or let's rather say to estimate. My guideline at that time was an article by Joe Curtin where he had measured the tap tones and weights of 5 different Strads. I could match the region of tap tones and weight and the overall thickness.

However In my experiment the sound of the violin in the white was completely without substance, muffled and dull. So first I wanted to throw it away but then decided to test at least a few varnish coats. To my surprise the sound became noticeably better in terms of loudness and overtone range.

In the end the top was not good enough for my standard. 

Conclusion was that measuring tap tones AND weight to get an idea of the sound is somehow complete nonsense as I was able to come down to the figures measured on Strads but the result was more or less a disaster. 

So there must be another and more important factor which I am not sure what it is. At least I can say that maybe measuring tap tones by frequency might be the wrong idea.  It could be more important to measure the damping  of the tap tones. So it is measuring more the clarity of the tapped tone which is in general completely neglected in all the research starting from Hutchins. (Or at least I can't remember anything in this direction) 

Secondly I was wondering what role the arching plays in the game. And there we come indirectly back to tap tone clarity. My gut feeling is that all could be related to the degree of squareness in the arching. 

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2 hours ago, John Harte said:

Possibly not so - At least, according to other researchers...

Re effects of varnish, Martin Schleske's article "On the Acoustical Properties of Violin Varnish" may be of interest to some.  See here:  https://stacks.stanford.edu/file/druid:yx381kq5616/CAS_yx381kq5616.pdf

Thanks John, will look into it ..

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19 minutes ago, Andreas Preuss said:

 My guideline at that time was an article by Joe Curtin where he had measured the tap tones and weights of 5 different Strads. I could match the region of tap tones and weight and the overall thickness.

However In my experiment the sound of the violin in the white was completely without substance, muffled and dull.

Thanks - very interesting report !

21 minutes ago, Andreas Preuss said:

So first I wanted to throw it away but then decided to test at least a few varnish coats. To my surprise the sound became noticeably better in terms of loudness and overtone range.

This seems to support the thesis, that varnish particularly could improve violins, which are on the "too thin side" ( my conclusion coming from your sound-description " muffled and dull" ). Matching the Strad-values, given by Curtin but coming out to dull, could point to a separate unknown factor, the Strads have for being not dull in spite of their quite thin graduations. However one should not forget the backs - so far as I know, Curtin could not give any values for them. May be, that you actually met the acoustical properties of Strad -tops quite well ( matching taptones, weights and thicknesses ) but you have had quite differing properties in the back of the violin....

44 minutes ago, Andreas Preuss said:

So there must be another and more important factor which I am not sure what it is. At least I can say that maybe measuring tap tones by frequency might be the wrong idea.  It could be more important to measure the damping  of the tap tones. So it is measuring more the clarity of the tapped tone which is in general completely neglected in all the research starting from Hutchins. (Or at least I can't remember anything in this direction) 

Quality or "clarity" of tap-tones could be a complicated thing : In my experience, it depends a lot of the fixing-point while tapping. If you met the nodal - line very good, then the ringing-quality is much better - there are also differences of more or less suitable tapping-points ( good anti-nodes ). Another topic would be doubled peaks in prominents modes, which are to see sometimes. Damping is surely involved. Clarity could also mean, that the plate produces a lower intensity of higher ( non-harmonic) modes. In general I like your idea, that there is much more than weight and some frequency-numbers.

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I find that the ground is by far the most important factor in finishing. One that is worked into the top wood with some form of calcium so the IR matches and it will then disappear in the coating. It creates a shell that dissipates the input easier and more evenly without the friction of the wood against itself. High frequencies are powerful and in order to have a crystalline sparkle to the sound there cannot be a lot of energy loss. Sure that can be had in the white, but with the varnish added there will be some loss and some gain in other areas. The most noticeable differences are when the instrument is taken to the point of no return then grounded and varnished properly,, I'm not saying that this is good in and of itself, that is just the situation that reveals the greatest change from white to finished in terms of sound modification. If it is observed that there is no difference between the finished and the unfinished state, then the unfinished state was in fact not finished.

I have experimented by adding ground over ground over ground with rubble and it will get extremely bright and sparkly until the weigh outweighs the benefit of the layers of rock on top. It is very brittle and can be chipped off to the wood by the fingernail with a scratch. There will be little if any measurable effects by eiginmode measurements. When it is scratched off it sounds very different, when regular oil varnish is applied it sounds still different.

There are many different substances that will change the properties of wood,, speed of sound, damping, and the ability for it to explode into a ball of fire.

Fun for violas!

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11 hours ago, Don Noon said:

Varnish CAN be a contributing factor in the sound of old Italian instruments in that there isn't much varnish on them.  

In my testing, coatings aren't very good at "improving" the acoustic properties of wood such as stiffness/weight and damping.  Sure, coatings can raise some frequencies... but I think if you could have added that extra weight in wood instead of varnish, you'd see even more change to the stiffness and no increase in damping.

The sound of an unvarnished violin is usually pretty obvious, and to my ear too harsh and wild (perhaps less so if you use dead-ish wood).  A little bit of damping to smooth things out I think is a good thing, but a full coat of oil varnish might be too much.  Coatings without oil, such as water soluble or resin/solvent generally are lower damping, and could help minimizing the effect.  And keeping the coating as thin and light as possible is obviously in keeping with the same theme.

People here tend to look at frequencies, which are easy  to measure, but I think the main factor is damping, which is extremely difficult to measure.

I think there are actually two possibilities with varnish.

Either the way you describe it, making an instrument which is in the white harsh sounding and using the right varnish composition to add damping to the sound. 

However you could think as well of making an instrument in the white with some damping and use a varnish composition which is aimed at decreasing the damping. 

This could eventually be a possible explanation why there are some Cremonese instruments with a rather thick ground. (More the the exception than the rule)

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56 minutes ago, Danube Fiddler said:

Thanks - very interesting report !

This seems to support the thesis, that varnish particularly could improve violins, which are on the "too thin side" ( my conclusion coming from your sound-description " muffled and dull" ). Matching the Strad-values, given by Curtin but coming out to dull, could point to a separate unknown factor, the Strads have for being not dull in spite of their quite thin graduations. However one should not forget the backs - so far as I know, Curtin could not give any values for them. May be, that you actually met the acoustical properties of Strad -tops quite well ( matching taptones, weights and thicknesses ) but you have had quite differing properties in the back of the violin....

Quality or "clarity" of tap-tones could be a complicated thing : In my experience, it depends a lot of the fixing-point while tapping. If you met the nodal - line very good, then the ringing-quality is much better - there are also differences of more or less suitable tapping-points ( good anti-nodes ). Another topic would be doubled peaks in prominents modes, which are to see sometimes. Damping is surely involved. Clarity could also mean, that the plate produces a lower intensity of higher ( non-harmonic) modes. In general I like your idea, that there is much more than weight and some frequency-numbers.

Measuring frequencies is a Newton based idea which I am sure was not in the mindset of 18yh century violin makers. At most they could have used a reference plate for comparison. 

Sure, clarity of tap tones is difficult to measure. I find myself often holding plates in various places left and right, upper and lower half for the same mode. Sometimes there are clear differences in pitch and/or damping which can be used finding the regions where to remove wood. 

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Varnish is usually adding stiffness as well as ground, but varnish is so dense that the stiffness/ weight ratio is decreased. Usually the ground does the opposite, so the outcome can be more or less about the same stiffness / weight.

White violins are way too harsh which changes after varnishing as Don already mentioned. Maybe varnish increases high frequency damping while lower frequencies are less affected, otherwise I could not explain the decreasing harshness. 

This effects are way stronger in oil based varnishes. When I was french polishing my guitars, the sound hardly changed before/after varnishing (of course the FP layer is usually thinner than a Alcohol varnish on violins, but there is still a tendency.)

Regarding the tap tones of free plates: If the great old used them, I think it was not more than a control of the end result. Otherwise there would be a lot more consistency in the frequencies, but that is an old and boring story :) 

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