Acoustic guitar bridges can sometimes develop cracks. Often a ‘fault line’ along the wood grain is to blame. Occasionally, it’s strings and bridge pins getting jammed in too tightly or pulling at the wrong places. Sometimes a crack is indicative of a more extensive problem around the bridge plate or the guitar top. Sometimes, though, it's just a crack.

How to repair a crack in an acoustic guitar bridge

Depending on the location and how extensive the crack is, you may be looking at removing the bridge and replacing it completely.

But you might get lucky.

Acoustic guitar bridge cracks can sometimes be repaired without replacing the entire bridge.

The bridge above has a long crack running between all six pin holes. There’s another couple around too but this big obvious one is the main issue. The crack doesn’t extend all the way to the bottom of the bridge. It seems to be about 80% of the way so I’m going to have a go at saving this bridge.

Mixing pigment into glue to match the bridge colour

What we’re going to use is superglue (cyanoacrylate). And, to keep the repair discreet, we’ll add a little pigment to colour the glue. Epoxy is a good alternative to superglue (better in many cases) but I want my glue a little less viscous for this particular job.

To match the bridge, I’m using lampblack. Traditionally, lampblack is a pigment powder that’s essentially soot collected from oil combustion. However, these days, you’ll find all manner of black pigment that doesn’t have the same ‘burnt hydrocarbon residue’ stigma. Check out pigments on eBay if you’re in the market (affiliate link).

I mix a small amount of the pigment with some medium viscosity superglue until I get a good dark liquid that I feel will flow well.

Because this long crack is relatively ‘open’, I’m happy that I can use a palette knife to get my medium viscosity glue to penetrate right down where I want it to. I don’t want to use the thinner superglue here as it could wick deeper into the wood of the guitar top (under the bridge).

Before I start slathering on glue, I place a few sheets of wax paper inside the guitar, under the pin holes. This will protect the interior in the event any black glue drips through. I also cover the guitar top to protect it. I used signwriter’s tape but some more sheets of wax paper would do the job too.

Mask off around the bridge to protect it from glue drips. Put something inside too to catch any drips that get through.

Then, I dribble on some glue. Superglue stays liquid for ages in larger amounts like this so there’s no real hurry. I can work it down into the cracks as I go.

I’m happy to leave the glue proud of the top as I’ll be sanding and cleaning up after it cures. And, it’s best to give it a while to cure. I’d give it 24 hours, just to be safe. Personally, I don’t like using superglue accelerator on something like this as I feel a natural cure is better for these larger, slightly more structural, repairs.

After sanding and polishing, the repaired bridge looks pretty good

After the glue is dry, it can be filed and sanded back. Successively higher grades of sandpaper can polish up the bridge and, all going well, the end result should be pretty discreet. Bear in mind that, if the glue has protruded into the sides of the pin holes themselves, or the hole-chamfer/countersink on top, these might have to be reamed or cut to clean them up.

For different materials, superglue can be coloured with different pigments. Very fine sanding dust, from the wood itself, can also work.

A bridge crack repair like this isn’t always possible or even recommended but in a lot of cases, it’ll do the trick nicely.

This article written by Gerry Hayes and first published at hazeguitars.com

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