Removing shellac overvarnishing. Help!


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I'm repairing a Furber violin at the moment.

It has had a hard life, and been 'cared for' for years by a chap who liked to put mahogany spirit stain mixed with spirit varnish on anything that looked a bit bare, and over any gluing he'd done, to seal it in.

So here I am, looking at a thinly varnished yellow violin, smeared all over with this stuff, wondering how to get it off.

Any ideas would be very much appreciated.

Conor.

 

 

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Hopefully if it is an oil varnish under all that stuff, try various concentrations of alcohol and water til you find a mix  that will take off that stuff and just soften the base varnish. I'm guessing that stain is into the base varnish and only solution is remove all.

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Removing over varnish, or any sort of retouching, is never straight forward.  Testing in inconspicuous areas, I generally try several different mechanical methods and solvents to see what is the most conservative approach to preserving the varnish and possibly texture below it. 

My "go to" method often ends up being scraping very slowly with a small curved scalpel blade (swann morton #15 being my favorite), checking often under UV light to make sure that i'm not accidentally encroaching on the original coatings.   Another mechanical method is using an artist eraser.  Occasionally soft over varnish, or over varnish that's been softened with solvents, can be pulled off in little balls with the use of a good quality white drafting eraser. 

Solvents are not straightforward, particularly with some shellacs that can become alcohol insoluble over time.  Often, I find that Im using solvents, I need to alternate between them. (For instance, starting with alcohol followed by acetone, etc) Solvents can also be too aggressive, slowing them down with castor oil, and wiping away the oil residue with white spirit can sometimes be useful.   

There is no magic bullet, and often a job can mean using all the tricks. Good luck!

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Rub the new spirit stain stuff off with ethanol or isopropanol, hoping that the varnish underneath is not spirit soluble. Even an old spirit varnish will not come off easily. But you can make a terrible smear with this method, you may also be lucky. Otherwise there is probably no such thing as fine grit sand paper.

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Just what Jerry said. 

in at least 98% of cases original and polish are interlocked and inseparable. 

It's not that the new layer just sits nicely on top, it has melted and mixed with into the original, into all the crevasses and nicks and craquelure.

The only way to get it off without removing big parts of the original is a lot of patience and many hours. Scraping with a scalpel is the slowest but safest method.

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Conor,

I Don't quite agree with everything what has been said above.

Overvarnish usually does not interact with the lower level. Picture restorers know much about this. Old paintings were often varnished and depending on the varnish could alter the brightness of the original painting considerably after 200 years or more. With the right solvant any overcoat can be removed without damaging the painting underneath.

Now for violins it is not quite as easy because almost any solvant which can attack shellack can attack the varnish below. If the varnish below is shellack as well it is getting really tricky. 

The best recipe I know is using hot water, distilled water is the best for that. It is a longish procedure but pretty clean. You soften the overcoat square centimeter by square centimeter with hot water until it whitens and if the overcoat is not toooo thick the whitish stuff should be  just what you need to remove. I use for this a bamboo spatula made from chopsticks. You need first to make a test in a hidden area if it really works.

Good luck!

 

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Thank you all very much.

I've had some success, mainly with Jacob's method. This stuff is pretty bulletproof to any solvents that I've tried, but very hard, so it grinds away quickly with the 800 paper, whereas the varnish beneath is tougher. It's such a pity to have to have to do this, as the original texture will be lost to some degree, and I'll have to retouch more than I like.

Unfortunately, I'll be facing much more of this. The repairer was very fond of his varnish brush, and worked in Dublin for about sixty years, so lots of my stock has been through his hands. 

Thanks again.

Conor

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