Relative humidity and your guitar.
Checking hygrometer settings in your home.
The wood in your guitar or other stringed instruments acts like a sponge - it absorbs moisture when the air is humid and gives off moisture when it's dry. Also like a sponge, it swells when it's wet and shrinks when it's dry.
Most guitar shops and factories are kept at 45% relative humidity at room temperature. This is right in the middle of the humidity spectrum. This way, if the guitar finds itself in a rain forest where it is very humid, or a desert where it is extremely dry, the guitar will only have to move (shrink or swell) a little bit, from the center of the spectrum, rather than all the way from one extreme to the other.
Too much moisture causes problems such as necks bowing or twisting and tops and backs swelling, which can drastically change the geometry of the guitar making it virtually unplayable. And keep in mind moisture loosens wood glue, so in extreme cases glue joints can fail. When a guitar is too dry cracks can occur pretty much anywhere on the guitar, sharp fret ends stick out past the edges of the fingerboard, and the finish can lift and flake off, among other problems.
Always make efforts to keep your instruments near 45% relative humidity at room temperature, but never below 40% or higher than about 55%. If you're traveling or playing an outdoor gig, do your best to avoid extremes like direct sun on a hot day, and keep the instrument in its case in a comfortable location when you're not using it. (As a musician you should also make sure you understand the concept of relative humidity and have a hygrometer wherever you store your instruments.) You can use in-the-case humidity products, or treat an entire room with air conditioners, humidifiers, dehumidifiers, etc., paying closest attention when the seasons change.
Also, get your guitars setup regularly to be sure they are always playing at their best, and so a professional can spot potential problems before they get serious.
Posted by willbright at 3:35 PM in
Care and Maintenance