If you are going to "repair" a guitar, there are certain adhesives for certain jobs. Do not use epoxy, for instance to repair a crack in the back or belly of a guitar with cleats, do not glue a big honking oversize plate over a crack with epoxy. In fact, I can't think of too many places where epoxy is appropriate other than filling an inlay space. perhaps.
Case in point: I have a disabled friend with little income who has a 1960 plastic-bridge LGO with a badly-bellied top, to the point it was unplayable. I am not a fan of the LGO, but for some reason these ladder-braced GSO's are gaining favor once again. Anyway, he paid a "luthier" to try to make it playable. His solution was to put a lower saddle in it, which only resulted in an unplayable guitar with rattle-y frets. I told him if he would pay for a new bridge, I would replace the plastic bridge with rosewood and flatten the top. Not a major problem. In addition to the belly-problem this guitar has two broken back braces and a loose top brace. Still not a big problem. The BIG problem is that this guitar has been dropped or stomped on or something. There is a huge multifaceted crack in the back that I'd thought I'd go ahead and repair...in for a penny, in for a pound. This looks like a puncture wound where some object intersected with the guitar back. Here's the rub: some previous "luthier" epoxied a huge rectangular patch of curly maple over the crack inside the guitar...without repairing and leveling the surface of the back. So the guitar back has a big crevasse where there should be nice clean nearly invisible glue joints. And removing the curly maple plate has resisted all attempts. I heated it thoroughly, to a point where titebond or Elmer's or hide glue would have easily released. In fact the heat blistered the lacquer on the back, without loosening the glue. It's OK, the finish will need touching-up anyway. I have used my bridge-plate chisel to try to pry or scrape it out. I have removed a few splinters, but the bulk of the patch remains glued fast to the back.
My next option is to take a sanding drum or grinder on my Dremel and try to get it thin enough to where I can use a cabinet scraper to remove the remaining glue. What should have been a simple 10-minute removal job has turned into an ordeal. Then I'll have to properly repair the crack...if they did not use the same epoxy on that.
No good deed goes unpunished....
Got it out, but it wasn't easy. Heated up a bent thin putty knife and kept attacking it by mm's...Now to clean up the rest of the ess and start putting it back together.
I hope after all that the guitar sounds good when the project is done. You are committing an act of real friendship. I hope your friend appreciates it.
I have a guitar where the bright sparks seem to have used epoxy in repairing the neck at the body joint - I now have to try to get the neck out to do a neck reset - sigh! I had heard there was some solvent for epoxy - acetone of similar but do not hold out great hopes.
'pickups' 8 days
'Preston Thompson OM-28 Custom' 11 days
'PickUps' 11 days
'test' 17 days
'1946 Gibson LG-2' 19 days