A customer brought in this ’70s Giannini 12-string that was in need of a rescue. As you can see, there are some problems at the bridge, compounded by a bad repair job that failed. A quick look inside showed that the bridge plate was cracked, and you can see that the bridge is barely holding on by the front edge. The customer’s budget added to the challenge, as did the ridiculously small soundhole. I could barely get my hand inside, and even when I did, there wasn’t enough room to work.
If I had to guess, I’d say that the heavy tension of 12 strings caused the belly to form and the bridge plate to crack, which eventually caused the bridge to come loose. Someone did a poor job of trying to reglue it, which caused it to come loose again, and this time it took some finish with it.
The first step was to remove the bridge without making the problem worse. It came off quickly, but the wood underneath was already damaged so a couple of big chunks came off with the bridge.
Step By Step Guitar Repair
The next step was to use a set of Thompson belly reducing cauls to flatten the top. It’s pretty straightforward: you just get them hot (I do it by dunking in hot water), and then clamp the matching set on the top and bottom of the bridge area. The small soundhole made it a bit of a headache. It took several tries, magnets, and help from my fiancée to get them in place. Since I also wet the soundboard, I left it clamped overnight to dry fully. After that, the top was pretty much level.
The bridge itself was unevenly arched and didn’t match the shape of the top. I flattened it with some razor files, then sanded it to shape by placing sandpaper over the bridge location. In a few minutes the bottom of bridge was the same shape as the top, which will help it stay glued in place.
Before gluing the bridge, I filled the existing string holes with some wax to keep the glue from dripping inside the guitar, and to keep the holes from getting plugged with glue. I figured it would save more time later, and it did. After the glue dried, I pushed the wax out from the inside with a bridge pin, and then a couple of turns with a reamer to clean up the holes.
Ovation Acoustic Guitar Bridge, Cp 100, 12 String
There was enough damage to the soundboard that I had to think carefully about how to repair it. With a bigger repair budget, I would have routed out the damaged wood and patched in a new piece of spruce, and if this were a valuable guitar I would have insisted on it. Since it was a family player, though a less costly approach was needed. I finally settled on using a 2 part epoxy because of its ability fill in the gaps without losing strength. I test fit the clamps and got the cleanup tools ready before I started with the glue.
Even with a specialty bridge clamp, I needed a few other clamps as well. The wings on the sides needed their own clamps, and I added a cam clamp to the back of the bridge to even out the clamping pressure It came out well, though I did need to wick in some extra glue at the front edge after removing the clamps.
Fitting a Bridge Doctor was the only practical way to make sure that the belly stays flat and keeps this all from happening again. It sits against the bridge plate underneath and is screwed in place. The long dowel pushes against the tail block, adding a lot of support to the bridge. It’s a bit of a brute force solution, but it’s also super practical and rock-solid.
Gluing Braces Inside A 1967 B 45 12n
Since it only requires about half an hour of labor to install, it’s an affordable solution as well. I measured everything outside of the guitar and trimmed the dowel to fit before installing.
The little piece of the bridge wing that broke off didn’t quite fit perfectly, so a little patching was needed to blend it in. I packed the joint with some rosewood sawdust and then applied thin CYA glue. After it dried, I scraped it level with the surrounding wood, then sanded it smooth. I also scraped off whatever that old finish was that had separated from the wood and yellowed over time. It made the bridge look new and the patch can only be seen up close.
The moment of truth: stringing it up to pitch. Not only did everything hold, but with just a couple of tweaks to the setup it played really nicely as well. The owner was excited to have her old baby back!Be it cold, heat, humidity or dryness, extreme weather and harsh environmental conditions are undoubtedly the biggest enemies of any guitar. The severity of the environment not only tarnishes the appearance of the guitar, but also affects its acoustic quality and structural robustness.
Epiphone Songmaker Dr 212 12 String Guitar
Extreme heat can melt away the glue, thereby loosening braces of the acoustic guitar. In such a case, warping of the guitar body can occur due to tension of the strings. This detaches the bridge as it's not designed to take the complete load.
The bridge can also get disconnected when high temperature softens up the bridge's glue. As a result of sliding of the bridge your guitar's intonation gets affected.
Tip. Never leave your guitar inside your car during summer, as the greenhouse effect will melt your guitar. Keep checking the acoustical quality of your guitar while traveling during summer to prevent such temperature prompted problems.
Maple Guitar Bridge Clamp, Multifunctional Guitar String Tool Luthier Tools
Humidity is equally detrimental to your guitar as temperature. With humidity in air, your guitar absorbs moisture and swells. The problem gets worse when the swelling is regional and a certain portion expands more than the others. This not only causes cracks to your guitar's body, but also affects its sound quality.
It's the low humidity that's more harmful for it. While the finished surface preserves its shape, the wood beneath shrinks due to low humidity. This shrinking can bend the top of your guitar from the mid-portion, where the bridge is pasted, causing the bridge to get loosened.
If the glue used at the bridge joint was not of good quality or if the proper procedure for pasting wasn't followed, chances are high that the bridge will loosen up. It's important to clean the area and sand it properly before the application of glue.
Vintage 1963 Gibson B 25 12 String Acoustic Guitar Natural Top
Tip. You must, therefore, buy a guitar only from a reputed brand. If the bridge has to be replaced, ensure that a good quality glue is used and proper pasting technique is employed. The surface should be cleaned and sanded to remove the wood finish as well as dirt before applying glue.
Although the bridge doesn't normally warp or crack, while it's attached to the guitar, these problems do come into picture when the bridge gets detached from the guitar. Once it loses its connection with the guitar, the tension of the strings can crack or warp the bridge. In some cases, extreme dryness can also crack the bridge.
Then you have the bridge plate, which is a plate or a brace that's fixed to the bottom of the bridge to provide support for the tension of guitar strings. It can also get damaged just like the bridge.
Mandolin Cafe Forum
Now that you know the likely problems that your guitar can have, it's time to see some DIY methods for fixing your guitar's bridge.
If you notice a gap between the bridge and the guitar, it's a clear indication that the bridge has become loose. However, if the gap is very small, you'll not be able to see it. You must try to slide a piece of paper in the joint. If the paper enters, there's a gap.
If there's a gap, you'll have to remove the bridge and refix it. Trace out the bridge on a card stock piece of paper and cut it out. This can be placed around the bridge to avoid any damages to the finish when you remove the bridge from the guitar.
Acoustic Guitar Belly Repair
Cleaning the Guitar Body. This is one of the most critical activities in the entire process. If the body isn't cleaned perfectly, the bridge won't stick properly. However, there is a chance of causing damage to the guitar body if adequate care isn't taken. I suggest the following procedure:
Cleaning the Bridge. This is also equally important, but a lot easier. Simply scrape off the glue from the bridge's bottom with a sandpaper. Take care that the surface curvature isn't changed due to scraping.
The top of your acoustic guitar has a specific curvature: its radius may be anywhere between 15 - 100 feet. Find out the radius of your guitar top and buy a radius block that matches with it. Stick the sandpaper on this block and scrape the bridge with it.
Rickenbaker 12 String Bridge, Ed Roman Guitars
If your bridge is cracked or warped beyond all hope, you may need to buy a new replacement bridge. Here are some.
If you
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