Spruce Top Classical

I purchased a spruce top classical. I didn't notice at the time but when I got to looking at it I noticed some clear glue blotches about a half inch square. It;s near the edge of the playing side of the lower bout. Someone had I would say laid down some clear glue to add a wooden arm rest and they got the glue bigger than the rest or moved it somehow. I do not know if it is lacquer or french polish. Is there a way to remove the glue without hurting the finish?
- Mike

Mike,
The first thing to try would be hot water.The glues that hold your woodwork together are water soluble. But, hide glue, PVR, etc. don't stick to finish very well and if, in fact, someone was trying to glue something to the finish, wood glue would be a silly bad choice. Try water because it's quick and easy. Another common malady is wood glue under the finish.

Clearing all of the construction glue slop is a fine point of instrument making. If you fail, and then put finish over the slop, you have a problem which looks like the problem you describe. It is rare, but also possible on plywood tops, for a spot of glue to leak to the surface in the pressing process. If your blemish is under the finish it may even be impossible to fix. You would need to remove the finish to expose the spot and then remove the wood that the spot is soaked into. That wood is now significantly thinner than the surrounding wood and will be an obvious ripple afterrefinishing. Working down a large area would remove that problem, but your luthier made your top a certain thickness for a reason.Losing a lot of wood from your top will effect your tone. And, if the glue squeezed up from underneath, you are screwed.

There are two ways to stick something to finish: dissolve and re-harden the finish, or put something sticky on it. Duco cement (airplane glue) melts lacquer and shellac (French Polish). A spot of Duco is part of the finish. It will need to be sanded down and replaced. There are various mesticks, on the market, that range from gummy to gluey. They all can be removed with a non-polar solvent, like mineral spirits, or peanut butter. Superglue stands between these two. It bonds to the water molecules on thesurface of all things. It is not technically a chemical part of the surface, but the bond between the glue and the water and the water and the surface is a mighty good one. There is a chemical sold as "Super Glue Remover." If all else fails, try some of that. Be careful, it will also dissolve your finish.

Hand made Classical guitars generally are finished with lacquer or shellac. These are soluble, removable and replaceable finishes. Old finish will melt into new finish. They are made of solids floating in a thinner. As the thinner evaporates, the solids clump together and make a finish. At any time the solids can be re-floated with fresh thinner. Essentially all production made guitars are finished with some kind of epoxy finish. In these finishes the thinner separates the A and B epoxies. As the thinner evaporates the As and Bs find each other and make a finish that is not soluble in anything. The good news is that whatever is spoiling your view would be on top of the finish (or under it). The bad news is that if you sand through, there will be a "witness line" around your new finish.

Anything to do with wood is quick and easy. Anything to do with finish is slow and difficult. Good luck.

Steve Mason