Adverse environment and misuse are the two main culprits behind the loosening and cracking of acoustic guitar bridges.
This article aims to bring out the likely reasons and types of problems that your guitar's bridge can have.
I will also show you how to repair a damaged acoustic guitar bridge, be it simply loose or broken altogether.
How does an acoustic guitar's bridge get damaged?
The bridge of an acoustic guitar can get damaged due to a variety of reasons.
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.
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.
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.
If you thought only high humidity is dangerous for your acoustic guitar, you're mistaken.
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.
A humidity of 50% is considered to be ideal for all stringed instruments as per most acclaimed luthiers.
Tip: It's recommended to keep a humidifier in your guitar's cover/case in dry winter months to prevent shrinking of wood.
Bad Quality of Glue or Pasting Job
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.
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.
Warping or Cracking of Bridges
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.
DIY - How to Repair a Loosened Bridge on the Acoustic Guitar
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.
This is not one of them 🙂
Here is how to correctly go about repairing acoustic guitar bridges:
1. Determination of the Problem and Preparation
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.
2. Bridge Removal
There are 2 steps to removing the bridge:
- Application of Heat: Heat helps to loosen the glue, so that the bridge can be removed easily. There are several ways of doing this; one of the simplest is perhaps placing a heating pad on the bridge. You could also use a hot iron while covering the bridge with a towel. Just take care not to heat it up too much, otherwise, you could end up damaging the guitar.
- Take Out the Bridge: Once the bridge has become loose, use a blunt putty knife and gently remove the bridge. Take adequate care not to disfigure the guitar or the bridge by overheating or by pushing the knife too hard. It should be heated just enough so that the bridge is loose and you don't have to apply force on the knife.
3. Joint Preparation
Now the surfaces of the guitar body and the bridge have to be cleaned and prepared. Here is how:
- 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:
- Line up the bridge using dowel pins.
- Temporarily paste the bridge in its place with a double-adhesive tape.
- Mark the outline of the bridge on the body using an X-acto knife.
- Protect the surrounding finish with masking tape.
- Remove the bridge and clean the marked area of excess glue using a chisel and/or sandpaper.
TIP: Be careful and go slow to avoid slipping with the chisel.
- 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.
If your bridge is cracked or warped beyond all hope, you may need to buy a new replacement bridge. Here are some.
4. Placing the Bridge
Now let's talk about actually placing the bridge onto the soundboard.
If you don't place the bridge in its correct place, you'll end up redoing the complete process. It's therefore very important to do it meticulously the first time itself.
A simple way of achieving accuracy is to mark the centerline of the bridge on the body of the guitar and front side of the bridge. This ensures that the bridge is placed perfectly in its place.
Use the existing bridge pin holes to line up the bridge accurately. You may put wooden dowels through the bridge's string holes as shown in the picture. These dowels can be removed by drilling after the bridge is secured in its place.
5. The Trial Run
After cleaning the surfaces, when the bridge is prepared and ready to be glued back onto the body of your acoustic guitar, clamp it in place before applying any glue. This trial is essential to test that everything's fine.
You can use a deep c-clamp for clamping the bridge and a board cutout of adequate size and appropriate shape to act as a caul. Fix this board piece to get the right amount of pressure. The effort is worth it because it saves you from the trouble of having to repeat the complete procedure.
This may sound unnecessary initially, but believe you me, it's very important. You don't want to have to remove the bridge again.
6. Application of Glue
If you're satisfied with the trial run, you're ready to glue the bridge to the guitar.
Titebond is one of the best wood glues for this joint. Normally, I suggest that glue should be used sparingly. However, this joint is very critical and you must use adequate glue for a tight connection.
After putting the glue, you need to clamp the bridge to the guitar body in the same manner as you did during the trial. This ensures that the bridge is fixed properly.
The clamp should be tightened until time some glue starts squeezing out.
7. Clean the Surface by Wiping Away the Extra Glue and Restring
The surplus glue that had come out while tightening the clamp must be cleaned using a paper towel or a damp piece of soft non-abrasive cloth.
Important: This must be done immediately before it sets in to prevent damage to the finish.
Allow adequate time for the bridge to set in. I generally leave it clamped overnight.
Take precautions while removing the caul and the clamp because it can dent the guitar from inside.
Restring the guitar, tune up and it will be as good as new!
It's very important to take care of your acoustic guitar and protect it from getting damaged. If you follow the instructions given in this article, you can not only avoid damage to your guitar, but also fix the bridge yourself.
If you have any queries, I'll be happy to help in the comments section below. Happy playing!