Can French Polish be applied to a guitar with blemishes

Construction and repair of Classical Guitar and related instruments
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fast eddie
Posts: 90
Joined: Mon May 15, 2017 4:39 am
Location: Columbus, MS USA

Can French Polish be applied to a guitar with blemishes

Post by fast eddie » Fri Jun 09, 2017 4:04 am

My question is this: I see quite a few guitars on e - b a y with marks on the top and/or the back. Can French Polish be used to improve the finish? I'm assuming it would probably have to be sanded down to the bare wood, but I don't know.
Thanks.
Fast Eddie
Cordoba C 10 Cedar
1974 Hernandis

Pat Foster
Luthier
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Joined: Sat May 13, 2017 4:12 pm
Location: Spokane, WA

Re: Can French Polish be applied to a guitar with blemishes

Post by Pat Foster » Fri Jun 09, 2017 1:37 pm

FP shellac can be used to re-seal nearly any type of damage, if the aim is to seal the wood to prevent it from getting stained from dirt. Whether it will show or not depends on the degree of damage and the original finish. If there's no damage to the wood, a shellac original finish usually repairs quite well, provided the tint is matched, which is one of shellac's strong points, since the new finish blends—bonds chemically— into the original finish, though older an original finish (on the order of many decades old) might not take the new finish quite as well. If there's a ding in the wood, a repair will likely show, though it could be made to stand out less with filling, depending on the damage and the wood, since repairs can be more easily made invisible or nearly so on dark woods. If the original finish is lacquer or a synthetic, it's a toss-up, depending on the damage and its location, but FP shellac will not blend into those finishes like it does on an original shellac finish. There's kind of an art to it. I think Frank Ford's site, frets.com, has some information.

Pat

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geoff-bristol
Amateur luthier
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Joined: Sun Nov 09, 2014 6:31 pm
Location: Bristol - UK

Re: Can French Polish be applied to a guitar with blemishes

Post by geoff-bristol » Fri Jun 09, 2017 7:27 pm

Shellac sticks well to most things if they are flatted off ( fresh soft cooked oil varnishes are a bit of a special case )
Generally, a sythetic finish as a ground would work ok. Trouble is - french polish is 'very' unfogiving to the slightest mark - and I mean slight ! Difficult to loose the dings - live with them ( character ! )
Scraping back old spruce is always iffy. Too much is needed to remove darkening - and thus one ends up a patcthy mess colour wise !

But shellac as a brightener/protector to old and warn surfaces is fine - nearly every Stradavari in existance has had a shellac polish over its lifetime !

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fast eddie
Posts: 90
Joined: Mon May 15, 2017 4:39 am
Location: Columbus, MS USA

Re: Can French Polish be applied to a guitar with blemishes

Post by fast eddie » Sat Jun 10, 2017 1:20 am

Thanks. I am considering buying an old guitar from a garage sale of pawn shop and practicing on it with French Polish.
Fast Eddie
Cordoba C 10 Cedar
1974 Hernandis

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