polyester finish

[Jerry Ryan]

What can be used to touch up, spot finish a guitar that has a 'polyester finish'

[Bob Webster]

Sometimes even premium flake shellac will show an adhesion problem on CA. Taking it to the extreme, I recently sealed a whole guitar body with CA (all except top) rather than shellac in preparation for French polish. Got done with the whole FP routine and then watched as a little piece of extremely low tack tape pulled little pieces of finish off of the peghead face. Words can't describe....

Fact is that set CA is a material akin to the standard acrylic polymer we call Lucite. It's plastic. So, to the point, we're asking shellac to stick to plastic and that seems to be a stretch when vast expanses are involved. On a spot basis, though, it seems less of an issue, expecially if the CA is roughened by light sanding. As for nitro over CA, it then follows that CA, like other polyacrylates, will dissolve in solvents commonly found in lacquer thinners, like acetone or MEK. Thus, the sinking that doesn't occur if you put some shellac in the way.

Bob

[Jerry Ryan]

Nick,

Your post identified you knew a bit about polyester finishes. I'm at the point with the Guild GAD50 guitar to decide to refinish the entire top. (it had been dropped on its tail, separated & broke the top above the tail block, cracks etc. ) I am planning to sand the entire top with 400 paper, then spray a layer or 2 of 1 lb shellac, sand lightly, then touch up the black edge of the sunburst near the tail where the CA repaired (cleated) cracks had caused a slight raise and the wood shows thu the black edge of the sunburst on the crack line after scraping and sanding. then finish the with nitro lacquer to get a consistant finish over the entire top. Reasonable plan? My apprehension is separation of the finishes over time.....

Jerry