Touching up PU finish
 

Hello,

Is it ok to use stained polyurethane varnish to do a tiny spot touch up?

I had a spot repair on the corner of a headstock, which I think was done with CA, and it has left it white-yellow. I’d like to make it blend in, and I was wondering if it’s safe to carefully brush stained PU varnish over it - eg deep mahogany PU varnish, such as can be bought from hardware stores?

Thanks in advance.

I think you are describing what I call a "Noxema" repair. The skill required to pull of such a cosmetic repair is beyond my ability. I generally prefer looking at the original damage/flaw to the ongoing distraction of the cover-up.

Thank you for the honest reply. I suppose I’d better leave it alone.

There are two reasons for the whitish appearance. The first is that the damaged finish was shattered or separated from the wood. The second is that the CA turned white from accelerated curing, which can cause foaming or bubbling. In either case, the only acceptable remedy is to remove the finish and CA down to the bare wood and start over. If the wood was originally stained, it needs to be stained to match before applying finish. The finish touchup can be clear lacquer or CA. With CA, an accelerator designed for finish touchup should be used. Odorless CA is less likely to turn white, since it cures a bit more slowly.

Thank you John for the informative reply. I think I’d better leave it alone and enjoy the guitar instead of cosmetically obsessing.