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Pumice and Tripoli


pt3
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I am in the middle of varnishing a violin, the ground of which was done with tripoli powder, the way Gregg explains in his article in the Strad Magazine.

There are several kinds of tripoli powders, for what I have seen. Some being more coloured than others. The one I used here is more towards the light side of things, but still rather pink.

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I have used pumice as well, for the same technique, and that super fine silica gel, and the results were satisfactory with all of them.

Apparently, though, the use of a mineral ground seems to be going out of fashion amongst the guys that know what is good.

Comments there??

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Apparently, though, the use of a mineral ground seems to be going out of fashion amongst the guys that know what is good.

Comments there??

We still use mineral ground, and find that it's possible to tailor the voice of an instrument quite a bit by small alterations in the composition of the ground. I wouldn't have believed it before I came here, but some of the instruments I developed for production owe a lot of the detail of the character of their voices to the choice of ground.

It's not for the impatient, nor for the person who only produces an occasional instrument. It took about 15 years of constant incremental experimentation and tests to come up with what we have now. This was facilitated by the fact that we imported a lot of European instruments in the white, graduated and varnished them for step-up student instruments. This provided a lot of instruments on which to experiment.

The exact composition of the grounds we use is the only company secret around here, but AFAIK, we don't use Tripoli for anything but rubbing out varnish.

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If I am not reading wrong, the latest research by Bradmair and Greiner found little trace of particulate grounds in the instruments had for research.

I am pretty confident that if Gregg uses it, there is no wrong on that...

Being a secret, a guess discussing those grounds is out of the picture...

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I was curious about the diatomaceous earth. I have just started using it for insects. It is food grade, I was wondering how abrasive it was being ground into a powder, and its possible uses for finishing, but this it the first time I had heard anyone mention it. Is it the same as rottenstone or are they two different things? What I have is almost white, thanks.

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There are lots of ways of getting the sound you want, and of course "everything effects everything." I think you have to be making pretty good instruments in their own right before choice of ground makes a lot of difference. What it does for my 5-strings, for example, is to provide a little more low end "bite" for the C string, and a little more overall focus for the sound. It just changes the "baseline" sound of the body, and makes it easier to get the exact sound I want through bridge cut, sound post, and other little details.

Other people might get similar effects by scraping the plates in specific spots, or thinning the ribs here and there, or some other favorite approach. The main thing is to do whatever you do, enough that you have control over the results. I think they key to really good sound is to get a model that works well for you (copy an established pattern), and then work with it until you really understand it, making small changes and observing the results, getting feedback from players.

Learning setup, too, is vitally important, IME. I can't count the times in the past I have been surprised by how big a difference tiny changes on a bridge can make, and I'm finally at a level where I pretty much know what to do to produce a particular change for a customer, and whether I can produce a particular change at all. I'm still in the minor leagues, but I feel like I do have some skills in a few areas.

Ground also affects the look of your varnish, and IIRC the refractive index of pumice is pretty close to that of many varnishes, and should help add depth to the look of the varnish. Won't hurt the sound, either, IME, so seems to me like it would be as good as anything for starters. Pumice is used as a filler for traditional French polishes, and a good French polish produces amazing visual depth from a very thin coating.

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I think tripoli is coloured in general - at least the one I have is coloured - so pumice is more suited to that, I guess.

Thanks a lot!

I remember that in your ground coating system you have used the diluted Marciana varnish, 2 coats, followed by gelatin sizing, and then the pumice-varnish paste. What's the purposes of using the diluted varnish and gelatine solution? For the purpose of easthetics (highliting the flames on the back plate) or used as sealers? But pumice-varnish paste itself is a good sealer, is it nacessary to use other sealers in advance?

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I was curious about the diatomaceous earth. I have just started using it for insects. It is food grade, I was wondering how abrasive it was being ground into a powder, and its possible uses for finishing, but this it the first time I had heard anyone mention it. Is it the same as rottenstone or are they two different things? What I have is almost white, thanks.

St. John Barley Corn,

Diatomaceous earth, fossil earth, infusorial earth, fuller's earth, Kieselghur, rottenstone or tripoli are all the same thing.

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