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French Polishing


johnsr

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The Milburn guitar website is absolutely first rate. Forget the premixed shellac--it goes bad in a few months and won't get hard enough as it esterifies--use only shellac flakes dissolved in alcohol. There is very very little oil used in french polishing. French polishing results in a very thin, soft finish that is beautiful and easily reversible. There is nothing quite like it for warmth, beauty, and a perfect level of shine. As you can tell, I like it. The best way to learn how to do it is to observe someone that knows how to do it and then practice--there is a trick to getting it right.

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With all due respect to Frank Ford, he's great sharer of knowledge, I don't think his french polishing technique is standard. Also, he's "repairing" an existing finish that was originally a varnish/french polish finish. It makes a difference whether you are finishing raw wood or repairing an old finish.

The "scuffing", coating with oil, etc. are not standard techniques in traditional french polishing, and the normal oil used is mineral oil (even baby oil), not a drying oil like linseed.

Still, I'm sure he gets good results.

The biggest challenge I've found in learning to french polish is knowing how wet (or dry, actually) the pad should be. Too much shellac/alcohol and you'll remove more finish than you deposit. Too little and the pad sticks--a little oil is used to reduce sticking only, not as part of the finish.

Fine pumice is also part of traditional french polishing. It's used both to fill porous woods in early coats and to smooth the finish in later coats.

It is a beautiful finish, and acoustically it's good because it's very thin. It is fragile, but also easily repaired and even restored to like new if that's the desire. That is much harder to do with lacquers and nearly impossible with some modern synthetic finishes.

It's not used the same way for violins, if at all, but it's an appropriate finish for bows.

A good video, though pricey I think, is sodl by Stewart-Macdonald. Ron Fernandez is the author, and it's a good primer. But the only way to learn is to do it.

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Jackc, there is an easy method to determine when the amount of shellac liquid is just right on the pad--press it against a piece of paper before going to the instrument. The perfect amount is indicated when there is a slight smudge (wetting) of liquid on the paper. Now you have the right amount for a rapid build of the finish.

When using pumice to fill a defect or the wood pores, the liquid on the pad must contain very little shellac (alcohol rich). The safest way to use pumice is to pick it up on a wet pad (place pumice on a piece of paper) because if you french polish pumice that is not completely wetted by the shellac solution, it will appear later as a white/grey ghost in the finish that will telegraph through for all to see.

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"French polishing results in a very thin, soft finish that is beautiful and easily reversible."

You might want to reconsider that last concept. Orange shellac, alone, is notorious for being nearly impossible to reverse after 50 or 100 years. I'm not saying that's absolute with every shellac and doesn't depend on the role the oil plays, but there's enough bad experience in this that modern violin restorers won't touch pure shellac with a ten-foot pole in restoration work.

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Barry, I think that's what Michael's been saying also.

Mike, I usually distibute the pumice with pounce bag--a cloth wrapped up like the pad with pumice only inside. Only very fine pumice comes out through the cloth, and only a little. I was not tuned in to using mostly alcohol when filling, though. I'll try that. I am aware of the paper test for the pad, I'm just not very well practiced in it yet.

I only use FP on old Gibson mandolins, as that's what they were finished with--varnish with FP as the last coat. Up 'til about 1927, I think.

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If you want to learn how to french polish you just have to do it to really learn. It's a "feel" thing. When you have the correct balance between shellac, alcohol and oil you can feel it going on smoothly and see the little evaporation trail that follows behind the pad. The basics that Milburn and the video from Stew Mac give are what you need to get started and then you find what works for you. It may be a blend of a couple of techniques that helps you get the finish you want. French polish is a very warm rich smooth finish but just as Michael said it will cover over the texture you want on a violin. A guitar is a different story. Usually only better classical guitars are FP. Steel strings are usually Nitro or some of the newer catalized finishes.

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There are probably luthiers that use french polish for the entire finish on a violin, but I do not think this finish is hard enough to last very long under the wear of a player. Shellac (seedlac) is used in the 1704 varnish which is used for restoration work, and I suspect a few people use this as the entire finish or a variation of it with some harder gums added.

I use french polish to help restore the shine on the repaired area after a crack has been repaired and leveled; so the french polish area does not get very far from the repair. That being said, the french polish layer is so thin that it would take a lot of work to get a thick enough build to alter the texture. I know how hard it is to get this level of thickness because I build classical guitars, and still the wood texture telegraphs through the french polish on guitars.

I can't say whether shellac becomes completely insoluble after a prolonged time so that it is not reversible. The shellac molecule contains some unsaturation so it is possible that polymerization can continue over long periods of time and that would lead to loss of solubility in alcohol. The lore is that shellac finishes become harder with time.

I used to use a pounce bag but there was one time when I did not get the pumice adequately wetted by the french polish solution, and I paid for it. That convinced me to place the pumice on a piece of paper and pick it up with a freshly wetted pad.

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  • 2 weeks later...

Pumice is used in French Polishing both during the "build" stage, to fill the wood's pores, and during the later stages as an abrasive to smooth the finish. I've applied with a pounce bag, which is just pumice wrapped in a cotton cloth like the pad. The cloth only allows the finer particles to come out.

Usually it's pumice that is used (4F grade-fine) rather than rottenstone or tripoli.

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Whatever you're doing to get a smooth finish, Jack, I can tell everyone that it works. (Remember that Austrian violin?) What do you think about the finish on this one? I had been describing it as having a "clear coat." Does this look more like "French polishing" to you (see attachment)?

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Sorry, Seth. I didn't do this. I was just trying to figure out if this is a clear coat brushed over the original or a french polishing. Something of the original finish seems to remain, but all the surface features (ie, grain and scratches) are obliterated. Someone worked hard on it, given the other repairs I see.

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