Acoustic Bridge Removal and Reglue
The bridge truly is the heart of an acoustic guitar. Typically made from a piece of ebony or rosewood, it is glued to the guitars top where it serves several critical functions for the instrument.
Via the bridge pins, the bridge serves as a firm anchor point for the strings to attach so that they can be wound to tension by the tuning machines at the other end of the instrument. The location of the bridge pin holes also sets the string spacing for your picking hand. Working together with and supporting the saddle, it helps determine the intonation. Lastly, its attachment to the top helps transmit the vibration of the strings to amplify the sound and create the tone that we all love to hear.
When strung to standard tuning, a set of light gauge acoustic guitar strings
exerts about 160 lbs worth of tension upon the instrument.
Since the strings are attached to the bridge, this pulling force is partially transferred to it. Though guitars are designed to resist that force, if there is any weakness in the glue joint connecting the bridge to the top, it can fail.
Though labor saving manufacturing techniques can contribute, to a bridge pulling,
in our experience, improper humidity control is often the primary cause.
When Does A Lifting Bridge Become A Problem?
Except in rare cases, a bridge does not typically pull completely off of an instrument without warning. Usually they start to lift slowly along the back edge and creep further over time.
While this may not sound like a big deal at the moment, it is potentially affecting the volume and tone of the instrument, and may eventually warp the top or progress to the point of complete bridge failure.
The bridge pictured is from a Taylor 914ce. A business card fits pretty far underneath the bass side corner. It was the same on the treble side. As a general rule, if a piece of receipt paper can fit further than 1/16″ under any one part of the bridge, it is due for repair. If paper fits under in multiple locations, regardless of depth, its also best to repair now. This one was a no brainer, it needs to be fixed now!
Bridge Lift Repair
If the bridge is up, it needs to be removed so that the problem can be fixed before it is reglued.
Occasionally we encounter instruments where an attempt has been made to “shortcut” a bridge repair by wicking glue underneath the lifted portion of the bridge and clamping it down without removal and refitting. In our experience, having re-repaired several this is a temporary fix at best.
There is a reason the bridge has lifted. For a proper repair, it is best to remove the bridge, fix the problem, refit the bridge to the top, and then glue it.
Preparing To Remove The Bridge
Even a separating bridge takes a fair amount of time and effort to remove from the instrument.
There are many different methods of removal, and they all have merit in their own way. Bridges can be shocked off using a hammer and chisel, routed off (if replacing), sliced free with palette knife, or heated via a lamp or heating blanket and pealed off with a spatula. In our shop, we often use a temperature controller and heating blanket system. When used properly, it makes for a reliably clean removal.
The layered blue tape in the photos offers some protection during the removal process. After removing Taylor Guitars proprietary ES2 Pickup from the bridge to avoid damaging it, we placed the heating blanket and thermocouple in position, holding them in position using a bit of tape and a couple of loose sockets that happened to be within arms reach. Though certainly not the most elegant solution, but they were more than sufficient. After just a few minutes, the bridge was ready for removal.
Once the glue has been sufficiently softened by heat, removal with a spatula should be rather smooth. Even still, experience is key here. If one is not careful, it is easy to gouge and tear pieces of the top of the guitar at this point. If you look at the photo above you will see that very few of the fibers from the top have been affected by the removal. That will make refitting the bridge easier.
Refitting An Acoustic Bridge
Regluing and Clamping The Bridge
Once sure that the bridge is well mated to the top, it is ready to be glued into position. We typically prefer titebond as the glue of choice because it has a reasonably long open time, is fairly easily removed if necessary, and it is easy to apply and cleanup. Hot hide glue is another, more traditional, option. However, it is a bit more work to prep and has a limited open time.
To hold the bridge in position while the glue dries we use specially designed clamps and cauls to reach through the sound hole and support both the top and bottom with fairly even pressure. Once in position, diligent cleanup ensures a nice clean job.
About Guitar Repair Long Island
Guitar Repair Long Island is the area’s premier destination for fretted musical instrument care and maintenance. Led by owner/head technician Erik Salomon, the shop is dedicated to providing quick, honest, and reliable service. Our vast experience in all aspects of instrument repair ensures that we can help with whatever your needs are. Contact us with any questions or book your appointment today.