Japanese black paint touch up

[Richard500]

I’m doing a rescue on what I’m pretty sure is an ordinary older Japanese bowlback that has a gloss black peghead and neck. I sanded both to clean up dings, but not completely to the wood. Rattle-can Rustoleum reacts with what’s left, and there’s lots of crawl that I wouldn’t see on most oil-based paint. I guess it’s take it all down again and try to seal it but if anyone knows what Japan might have been using, say just post-war. I can’t think it’s traditional bug lac as it’s thick and it would be too slow.

[HoGo]

Could be the traditional asian urushi lacquer. You can try to use thin isolation layer of shellac if your overspray reacts with what's underneath.

[MikeEdgerton]

I love shellac. You can put it over almost anything and put almost anything over it.

[rcc56]

I don't know what might have been used originally, but Rustoleum would not be my choice for the job.

If you want to spray, you might consider black nitrocellulose lacquer.
If you don't want to spray, you can use either a spirit varnish, dyed with aniline dye or Fiebing's leather dye, or an oil varnish, dyed with artist's oil color, available at any good artist's supply shop.
And yes, shellac will stick to nearly anything, though I did run into something it did not stick to a while back. Wish I could remember what it was.

[sunburst]

...if anyone knows what Japan might have been using, say just post-war...

I don't know what they would have used, but since others have proposed possibilities...

I've had good success matching old Gibson and old Martin black paint by mixing powdered lamp black pigment with blonde shellac. Whether or not that would match your project I do not know, but there are other black pigments so you could experiment for a good match.
I have not had good luck mixing semi-liquid pigments (from a tube) with shellac because of very slow cure times, so I prefer powders.

[rcc56]

To clarify, the artist's colors in a tube should not be used with shellac or other spirit varnishes. They can be used with oil based varnishes. And oil varnish is great stuff, but the cure time is very slow. Violin people still use it, but most mandolin and guitar people prefer something quicker.

I can't say for sure what I would use without the instrument in hand, but I mostly use either nitro or French polished shellac these days, depending on the look of the instrument. By my old fashioned standards, nitro gives a more "modern" look, and shellac is more "old-timey."