Acoustic guitar debelly

A while back I wrote a blog detailing how to fix an acoustic guitar with a belly, which has somehow become one of the top hits on this here blog. One of the people who saw that blog post was my new friend Kip, who had a similar problem with his 1950s era Gibson that he apparently found in a barn. Despite being covered in a layer of dust a centimeter thick, it was in surprisingly good shape: the only major problems was a significant belly in the top, a worn out bridge plate, and some uneven frets. Kip couldn’t find anybody in his area that could fix it, so it drove it 400 miles from Tyler, Texas to bring it to me!

The string tension had over the last several decades pulled on the guitar’s top, causing a belly and causing the bridge to lift. Apparently someone along the way had attempted to glue the bridge back down, but they didn’t address the underlying problem, and so the bridge began to lift again:

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The first thing to do to address fixing an acoustic guitar belly is to remove the bridge. Now, normally I do this by heating the glue using a heat lamp, with a heat shield protecting the guitar’s finish. However, this time I couldn’t use this technique, as Gibson had apparently sprayed finish over the bridge as well, and the heat would have melted the finish on the top of the bridge (or worse, lit it on fire!). Also, the two pearl dots on the top were hiding two bolt heads, which were threaded onto two nuts on the inside of the guitar on the bridge plate. So how to apply heat without ruinin gthe finish? I fired up an electric hot plate, and warmed the metal blade on my bridge spatula, and carefully cut through the glue under the bridge, like so:

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Once the bridge was off and any remaining glue was cleaned up, I again went back to the hot plate and heated up a set of Thompson belly reducer cauls, and clamped those to the top – he heat of the cauls plus the clamping action would help reduce the belly to back to normal. I did a series of these heat presses before I got the top back to a position that I was happy with.

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While I was allowing the heated cauls to cool, I cleaned up any excess wood and glue from the bottom of the bridge with a razor blade. Then I took the clamps off, and checked the curvature of the bottom of the bridge vs. the newly flattened soundboard, which now revealed a significant gap in the middle of the bridge. I couldn’t just very well glue the bridge back down as is – it would start pulling up in the middle again. As always when I do this kind of work, I would have to shape the bottom of the bridge to match the top’s curvature by taping some sandpaper to the guitar’s top and sanding the bridge to match – but wait! The bridge was bolted down! Now what?

There was no way to shape the bridge without removing the bolts, but the bolt heads are hidden under two pearl dots, which have then been finished over. This was a 60 year old Gibson, and I couldn’t disrespect the guitar by drilling out the original pearl dots to get to the bolts. Even though the glue I was intending to use would render the bolts unnecessary, I couldn’t just cut them off either. What to do? Apply heat! Gibson used hide glue to put their instruments together back in the day, so it was safe to assume they had used it to glue the pearl dots down. Perhaps I could melt the glue and push them out without damaging them. I first scored the finish around the dots with a razor, then applied heat to the exposed end of the bolt with a soldering iron:

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After about 20-30 seconds, I pushed the bottom of the bolt, and sure enough – the dots popped right out!

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Sweet! Now I was free to shape the bridge to match the top!

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Now the bridge mated to the top perfectly, I had to put the bolts and the pearl dots back in. Some of the finish around the dots had cracked, which was largely unavoidable and expected. I used a bit of amber superglue to blend back into the original finish, which normally you wouldn’t want to mix with nitrocellulose lacquer, as it tends to melt the finish. But this time, melting a tiny bit of the original finish was exactly what I was going for, as it would help blend in. With some carefully placed amber superglue and some judicious use of micromesh, it looked just like it did when it came in. Success!

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From here on out it was smooth sailing. I glued and clamped the bridge back down (using Tite-Bond wood glue – strong stuff), and once it’s dry it will hold for another 60 years. Huzzah!

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Once this guitar is done, I plan on driving it back to Tyler, Texas to deliver it back to Kip. Now, normally I don’t make 400 mile trips to deliver a guitar, but my little sister is giving birth to my very first niece in Dallas, and I will be driving up to meet this new little human being, and Kip’s place is on the way. I didn’t want him to wait until Mardi Gras to come get it (his original plan), so I guess this was meant to be! Right on!

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