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Gregg Alf's ground - question


jackc
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Having never really gotten the idea of the ground coat, I liked what I read and what the photos showed in a Strad article by Gregg Alf in the Nov. 2006 issue. He described his method for mixing and applying an oil-based ground coat for his violins. To quote fomr the article:

quote:


...I make a traditional paste sealer of porous particulate matter--for example, tripoli--in a short-oil and high-resin medium similar to the the varnish used in the finishing process.

My question is about the terms "short-oil" and "high-resin".

By short-oil, is he referring simply to linseed oil, or do the terms go together to mean that the sealer has a high ratio of resin relative to oil?

Would it work to take something like DMOV and mix it with tripoli and use that as a ground coat?

The thing that I think will look good about this sealer is the coloring of the pores of the wood. I've done a similar thing with mahogany on a guitar and the effect was very nice. I just don't want to misinterpret what Mr. Alf is saying and create something that has to be undone. Any ideas from the collective wisdom? Thanks.

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Gregg's Ground Sealer Recipe

I tbsp Tripoli (Kremer 99930)

5-10 ml Short Oil Varnish *

1 drop Cobalt drier (Less is better)

*Varnish is said to be "short oil" if it has less than 50% oil in the mixture. As the varnish gets "shorter" it gets thicker and less runny. For Gregg's ground sealer it should be pretty thick stuff.

The lecture summary can be found here:

http://www.alfstudios.com/news/articles/SCVAM.html

I have not found the composition of the varnish, but it is very dark colored

Mike D

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Jack, in violin varnishing the purpose of the ground is to prevent varnish soaking into the wood, and to control how the wood looks under the varnish in terms of reflectivity, clarity, apparent depth. Sometimes the ground also might be used to affect color and to act as a final smoothing of the surface.

Violin varnish grounds need to appear transparent, so the rationale is different from the typical filling of pores in furniture or guitar woods with an opaque pore-filler.

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In conversation with a maker on this board (I won't name him lest I should put words in his mouth which he didn't speak) I recall him saying he used pumice instead of rottenstone. Finer was not necessarily better. Not sure why Alf is using Tripoli for this. I used pumice on my 2nd violin and it worked out pretty well. I think it was Ispirati on this board who, after discussing rottenstone versus pumice, did an experiment with both and ended up deciding he liked the way the pumice worked better.

To the Original Poster: yes, Darnton Mastic Varnish should work just fine with this. That's what I used for the spruce on my 2nd violin, and it worked just great. I used Fulton varnish for the ribs and back.

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The next question after finding out Alf"s method for the maple portions of the instrument is to ask---- How does he treat the spruce?

The article I referenced above does not go into it. The varnish that is mixed with the tripoli (pink colored) is very dark (it appears to be black in the bottle and dark brown in a thinner layer) and would lead to a blotchy spruce top unless it was sealed, first. I assume Alf seals the spruce but I would like a clear statement on that. In an earlier article in the VSA, Alf says he uses Liquin, first, but it is clear that Alf is always changing his technique as he is learning.

Mike D

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