Removing patches from inside guitar

[Enrico Schiaffella]

Hello there, I have this classical guitar that was badly repaired. Someone glued huge patches of wood inside the guitar. In the soundboard. The sound was Killed. Do you think it’s possible to remove these chunk of wood without opening the instrument? I don’t think it is. The wood was glued in the area just below the bridge going near the tail block. Very difficult to reach with a handplane.
Thanks Enrico

[Chris Vallillo]

I am currently doing a similar process on a Harmony H-165. In this case, someone modified the guitar to have a "through the top" bridge rather than the original "through the bridge only" arrangement Harmony used on these guitars. In the process of drilling pin holes, they damaged the re-enforcement plate beneath the bridge with enough tear out to compromise the integrity of what is essentially now the bridge plate. I'm going to remove it and replace it with a slightly larger one of rosewood to increase the stability of the bridge and top.

What I am doing is saturating a paper towel, then placing it over the offending section of wood on the inside. Since this is on the top, I turn the guitar over on it's face and let it sit overnight. By morning, the wood will have been saturated and I will then slowly and gently heat the entire area with a hair dryer. This piece was originally installed with hide glue so the combination of heat and moisture will soften the glue enough to use a bridge plate removing tool to pry it up and off. I've done this on multiple instruments with very good results. The piece usually comes out intact.

I've also used this with Tight bond types of glue with good results as well. The trick is to go slow and easy. Make sure the wood is sufficiently wet to reach the glue, then heat slowly until the entire area is slightly hot to the touch all the way through (reach inside to judge how warm the "bridge plate" is) then proceed gently with the removal.

[Enrico Schiaffella]

Hi Chris thank you for your answer. The paper towel trick is something that I might try. I don’t know if I’m ready for this. I find it a bit risky. The wooden patches are very close to some braces and overlap the center seam. Also I don’t know what kind of glue it was used. But I don’t have many alternatives. I tried to plane it with a small handplane but it’s very difficult if not impossible to reach the majority of wood. But I am interested in your procedure. I might give it a try. Many thanks Enrico

[Clay Schaeffer]

Saturating paper towels with vinegar will loosen many glues more effectively than water, but if it saturates braces it will also loosen them. Vinegar is like a weaker form of Goo Gone. They both have acetic acid in them.

[Chris Vallillo]

I just did the very thing on the Harmony I spoke of in the earlier post. In that case, it was a piece of spruce about 1 1/2" X 6 1/2". After leaving the wet paper towel on overnight, a bent, sharpened knife easily slid underneath the piece and separated it with little trouble. The only tough spot was in the very middle where the glue hadn't become fully saturated yet. That had been hide glue, by the way.

Clay makes a good point about the vinegar. I need to remember that one myself!

In your case, I'd try to keep size of the "paper towel" or whatever you put on the pieces you want to loosen just a bit larger than the piece itself to avoid causing unwanted damage. small pieces probably won't need as much time. When I'm ready to try to remove it, I heat the area from the outside with a hair dryer to assist in the softening. I do that slowly to avoid finish damage until I can reach inside and feel that its at least warm to the touch on the inside.

Remember, time is your friend. Go slow. Good luck!