The summer in North India (at least the first few months) is a time for dry weather with the humidity wavering around the 40% mark. This is a bad time for your acoustic instruments. Why?
The wood of your instrument loses its moisture to the atmosphere when it is hot and dry. Add to it the tension of the six strings (and imagine the tension on the neck of a 12-string instrument). That twin effect can bend, bow and crack wood easily. Remember that’s 90% of your instrument that I am talking about. In extreme cases of neglect, the instrument may be damaged irreparably.
What lack of humidity does
The top and back of your guitar are actually two pieces each (in all four pieces) which are glued together. Look closely and you will be able to see the seam where the two pieces of your top or the back are glued.
‘Dehydration’ shows up here first as the seams slowly start opening up as the wood shrinks, losing moisture. One day, running your fingers across the top or the back you may find your fingernail catch on something. A week or two later, you may actually ‘see’ the crack, and a month later, a toothpick may drop through it!
The fretboard – generally made of rosewood or ebony – is open-grain wood (without any finish on it) and thus, loses and absorbs moisture very quickly. A continued spell of dryness will certainly lead to cracks in the fretboard, which may lead to frets popping up, sinking, or simply hinder playability.
As the fretboard shrinks, the fretwires stick out (called fret sprout in technical jingo), making playing the instrument a difficult, if not a completely dangerous proposition.
The shrinking wood even breaks away at places like right next to the fretboard extension on the top of the guitar, or, along where the pickguard is stuck. Old Martin guitars were notorious for acting up like this.
What can be done?
Acoustic instruments wish to remain in that optimum range of 45 to 60% humidity. The first thing, come March, is to keep a close watch on the hygrometer (in your smartphone). Otherwise, it is a relatively simple and not too expensive instrument. If you have an expensive instrument (money-wise or sentiment-wise) I will advise that you buy a proper hygrometer – both analogue and digital are available – and keep it your guitar case at all times.
However, keeping a hygrometer in the case does not measure the humidity ‘inside’ the guitar. It only measures the ambient humidity of the case. To keep proper tabs on the humidity in your instrument, you will need a small hygrometer that you can place through the soundhole of the guitar. Put it inside. Cover the soundhole and leave it like that for the next 48 hours. The reading that you get, then, is the real humidity of your instrument.
The first photograph of this post is of a hygrometer measuring 1.88″x1.12″x0.59”.
Even if you don’t wish to go through the above exercise, knowing that the outside humidity is at or below 40% should be enough to give your ‘thirsty’ instrument a drink of water. But don’t soak it in the bathtub yet!
There are many, many implements available in the market to humidify your acoustic guitar, but then nothing as cheap and as effective as what I do. Take a small plastic container (that can go through your soundhole) and a piece of your old cotton t-shirt. Soak the t-shirt in water, put it in the container, and put the container through the soundhole into your guitar.
Cover the soundhole with something so that the moisture does not escape from the instrument but is absorbed into it. Leave it like that for at least 72 hours and then check the dampness of the cloth that you left inside. If the cloth dries out, wet it again and repeat the process till you find that the cloth continues to remain as wet as you put it in.
And, of course, you have the hygrometer inside to actually check the humidity reading.
To take care of the neck and fretboard, leave another dish of water-soaked rag in the case of your guitar. But be very careful that it does not topple and wet the case or the instrument.
How ‘the drink’ affects
Try and imagine a raisin. Try leaving it in a bowl of water for two nights. By the third day, it is swollen, with the water it has absorbed.
The wood on your guitar is pretty much like that. After it has had that ‘drink of water’, it will swell. What that will do is that if, earlier, your fingernail would catch on the seam of the top or the back, now it would smoothly glide over it. Cracks closed!
However, it would be wrong to think that just putting in a cup of water inside your guitar would cure it of its cracks. There might be some which may get better but not close completely. In that case, you will have to find a guitar tech and get it proper attention.