When the relative humidity of the environment is too low, your guitar can lose too much moisture. This can pose a threat to acoustic guitars because they can dry out and become prone to cracking and other damage. Even quality acoustic guitars under $1000 are prone to becoming too dry.
How do you know your acoustic guitar is dehydrated? Here are the signs to watch out for.
1. The top or back of the acoustic guitar has begun to collapse or arch inwards
Moisture loss in the wood of the guitar makes the top or back of the instrument shrink or contract, resulting in a noticeable change in the body’s contour. Acoustic guitars are built with a slight arch on the top. If your acoustic guitar is too dry, the wood contracts and the arch will flatten and can even become concave. The top or back will begin to dip into the body of the guitar.
The bracing in the top and back would stop some parts of the wood from shrinking, which means some parts sink and some don’t, resulting in an unevenness in the top or back.
2. The string action has become too low
When the wood of the guitar becomes dehydrated and the arch in the top sinks or begins to collapse, the string action – the distance between the fretboard and the strings – also changes. This is because the bridge would also sink, pulling the guitar strings closer to the fretboard and bringing the action down.
An extreme lowering of the string action makes the guitar difficult to play cleanly because you will hear a lot of string buzz when fretting, especially above the 7th fret.
3. The bridge lifts up
Another possible scenario with a dry guitar is the lifting of the bridge. The grain of the bridge runs in a perpendicular direction to the grain of the wood on the top or soundboard of the guitar. This means that the bridge does not shrink or contract in the same direction as the soundboard. When the soundboard shrinks, the bridge may begin to come loose and separate from it, making it seem like it’s lifting up. What’s good about a lifting bridge is that it can prevent the soundboard from cracking, which is a bigger problem.
4. Cracks have begun to appear and the grain of the wood has become very pronounced
The more the wood in the guitar loses moisture, the more the lacquer begins to get drawn into the wood to replace lost moisture. This results in a more pronounced wood grain or a washboard texture. Small cracks can also appear on the guitar’s lacquer, indicating that the wood is shrinking or contracting at a rate faster than the lacquer can cope with.
5. Small lumps appear in the finish
Compared to the wood used in an acoustic guitar the finish is a more stable material. When it is applied, the finish fills the pores of the wood. When the humidity is low and the guitar loses moisture, the wood begins to shrink, causing the finish filling the wood pores to pop up and appear as tiny lumps on the surface.
6. Outlines around inlays and the rosette appear
You can also check the inlays, the rosette and the purfling on your acoustic gutiar for any signs of dehydration. Take a look at the these and see if a line appears around them. If there are noticeable outlines, it means that the wood is too dry. As the wood on the acoustic guitar contracts, it shrinks away from these non-wood materials, causing a minor separation.
7. Cracks appear in the wood of the acoustic guitar
Aside from cracks in the lacquer, one telltale sign that your acoustic guitar is in severe need of humidification are cracks in the wood, particularly at the top or soundboard of the guitar.
When the top shrinks too much because of dehydration, the tension builds up and eventually releases in the form of cracks. The first crack would usually appear right under the bridge going down to the bottom of the guitar, on or near the center seam. This is a severe condition that needs to be addressed as soon as possible to keep the guitar in working order.
At the back, you may also see that the seam at the center would begin to open as the wood shrinks. And if your guitar is very dry, it can split along the the sides as well.
8. The fret ends have begun to stick out
As the wood of the fretboard shrinks, the metal frets, which are stable and are not affected by low humidity, become more exposed and begin to protrude. The fret ends also stick out from the edges or sides of the fretboard and feel sharp.
Additionally, cracks along the sides of the fretboard where it is glued to the top may develop. When the top dips or collapses, the fretboard would also tend to get pulled down into the guitar’s soundhole. This is another severe warning sign of acoustic guitar dehydration.
What to do if you see these signs
If you do notice one or more of these signs in your acoustic guitar, it’s best to take it to a luthier or professional guitar technician right away for proper diagnosis and repairs.
If you don’t see these signs, you should still be concerned about the relative humidity in the space where you store your guitar. The ideal humidity range for an acoustic is between 45 and 55 percent.
You can use a digital hygrometer to monitor relative humidity levels and a humidifier to make sure your instrument has the right amount of moisture to keep it from getting damaged by low humidity. You can also invest in a room humidifier for the space where you store your guitar, especially if you live in an area where the climate is really dry.
Preventive maintenance is key to ensuring your guitar doesn’t become dehydrated and damaged. This would also help you avoid costly repairs down the road, so make sure your guitar gets just the right amount of moisture to keep it in top condition.