how to prevent acoustic guitar belly bulge

Belly Bulge: How To Prevent An Acoustic Guitar’s Belly Bulge

Is it really that important to learn how to prevent an acoustic guitar’s belly bulge? Let’s find out.

A belly bulge in acoustic guitars is one of the most common issues for every acoustic guitar owner; that is why owners who have knowledge on how to prevent an acoustic guitar’s belly bulge have a really huge advantage.

Acoustic guitars can last for a long time when taken care of properly. Cheap guitars can reach up to 10 years, while premium acoustic guitars can reach 20, 30, or even more than 40 years with the correct maintenance. Although problems like belly bulge can still occur as the acoustic guitar gets older, fortunately, it can also be prevented in some ways.

So, what is the bellying of an acoustic guitar’s body really? Bellying is the bowing of the soundboard of an acoustic guitar. It is the constant tension applied by the strings that causes the bridge to rotate forward towards the neck, resulting in the warping of the top side, a slight drop at the sound hole, and a raised action.

How To Determine If Your Acoustic Guitar Is Having A Belly Bulge?

The first is one of the simplest methods in determining whether your acoustic guitar has a belly bulge. Lay the acoustic guitar on a flat table, find a ruler, and lay it flat directly behind the bridge, and if the top side has bowed, gaps should be visible between the side of the ruler and the top part of the guitar.

The second test is to use a ruler and lay it over the top of the acoustic guitar’s bridge pointing down the neck, and if the guitar’s bridge has rotated forward, the ruler will point downwards towards the acoustic guitar’s sound hole, which means that there is a belly bulge in your guitar.

Do not worry when your acoustic guitar has created a dome in its bridge, as nowadays, flat-tops are already non-existent, but for its general rule, it is considered that there is a belly bulge that is severe when it measures two to three millimeters and upwards as a bowed top.

What are the reasons why your acoustic guitar has a belly bulge?

There are lots of reasons why an acoustic guitar has a belly bulge, and it is very important to learn what these things are to prevent it from ever happening again.

One of the possible reasons is the tension of the strings. String tension pulls the acoustic guitar’s bridge forward, raising its action and resulting in your acoustic guitar’s belly bulge. Acoustic guitar strings also tend to have higher tensions, so it needs to be constantly checked to avoid this problem.

Another possible reason for your guitar’s belly bulge is humidity. When you feel that the acoustic guitar has a higher action than before, your guitar may be wet. When your guitar is wet, it also means that it is exposed to too much humidity, possibly above 60 percent.

When your guitar is exposed to too much humidity, the worst-case scenario would be that the guitar’s finish can begin to lift or crack, glue joints can fail, and splits can form in the top due to bulging of the belly.

Sudden changes in temperatures can also be the cause of your acoustic guitar’s belly bulge. Acoustic guitars are mostly made from wood which is always affected when it comes to temperature changes. Extreme temperature changes like exposing it to the sun for a very long time will affect its shape, like belly bulging, and could lead to splits if unresolved for a long time.

What are the methods on how to prevent an acoustic guitar’s bell bulge?

The first way to prevent an acoustic guitar’s belly bulge is to change your strings, possibly with lighter tension strings made especially for an acoustic guitar. Heavier gauge strings tend to have a heavier pull, leading to its bridge going forward and raising its action, resulting in your acoustic guitar’s belly bulge.

This is why lighter gauge strings are better for preventing belly bulges on acoustic guitars.

For areas that have a higher humidity than other places, it is recommended to place several silica gels or bamboo charcoal packs in your acoustic guitar’s hard case or gig bag and change them every few months.

You can also use a room dehumidifier to where you store your acoustic guitar and use a digital hygrometer to regularly monitor the humidity levels of your place. You should also remove your guitar from its case periodically and blow-dry the interior of the acoustic guitar’s case with a hairdryer for ten minutes.

You should avoid placing your acoustic guitar in very hot or cold areas for a very long time as these can affect the shape of your guitar and possibly cause your acoustic guitar’s belly to bulge.

How do you fix a bellied guitar?

There are many ways to fix a bellied guitar, and these are some methods that you can try on your own acoustic guitar if you are having this problem.

The first method is to remove the acoustic guitar’s bridge and focus on the top directly. You can use a cork board and lay it on the guitar to protect the top and heat the bridge with a lamp. This will melt the glue that is holding the bridge to the top, allowing you to slide a knife into the glue joint and lift the bridge.

With the bridge removed, you can use convex cauls placed on top and concave cauls placed inside the guitar on the bridge plate. These aluminum cauls must be heated in boiling water just enough to melt the glue before placing it on the acoustic guitar’s bridge. Wear a glove and use tongs to remove the cauls from the boiling water.

After removing the cauls, set them in place and clamp them down. The convex and concave cauls will reshape the top, pressing it flat. The heat and pressure from the cauls will do their job, and you just wait for it to cool down and the glue to set. Lastly, put the acoustic guitar’s bridge back on, and the top side of the guitar will be as good as new.

Others also remove their acoustic guitar’s bridge and rub them with sandpaper to level the base of the bridge and the top surface where it is placed.

You can also reset the neck or bridge or fill the bridge saddle for temporary repairs with belly bulges in an acoustic guitar.

Overall, it is essential to learn how to prevent an acoustic guitar’s belly bulge in order to preserve its condition and maintain its playability. With the correct maintenance, you can extend the lifespan of your acoustic guitar for many more years.

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