scratch repair question

Dan Noren

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falcon heights, minnesota
a friend of ours lucked into a perfectly good epiphone 350-12. the finish, front, sides, and neck is still in a very smooth condition, but the back has some small light scratches and such in it from being tossed in the dumpster. last night he asked me what kind of finish it was (i'm guessing poly), and what would be the best way to fix the scratches. i told him that i would bring it up here, and see what happens. thanks guys!
 
My last guess would be poly - pretty brittle and not easily rubbed out and polished. Most string instruments are finished with lacquer or varnish. If it is lacquer, you may be in luck - since lacquer is solvent based, you may be able to soften the existing finish enough to fill the scratches with just some lacquer thinner. I know luthiers have tricks for repairing varnish finishes, but I don't know them.

To determine if it is lacquer, put some thinner on a Q-tip and work in the most hidden corner. If it is varnish, the lacquer thinner will have no effect, if is lacquer it will soften.
 
Almost certainly poly. How bad are the scratches? If they're not through,you can likely buff them out with automotive polishing compound. If they're deeper, you can fill them with CA glue, scrape or sand flat and buff. Won't be completely invisible, but not bad.
 
If the scratches are deep enough to catch your fingernail as you go across them, and you know it's a poly finish, you can get a tiny artists pointed brush an paint poly into the scratches in several coats until you've built them up slightly higher than the rest of the finish. then carefully wet sand the high areas back flush with the rest of the finish using a flad block or pad, then buff it out. The scratches should disappear.
 
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