Jim's Guitar Tip-O-the-Month Feb 1999

This year, we've seen more guitars than ever before damaged by loss of moisture. As the temperature falls, that same gas furnace that keeps us nice and warm, also dries out the air in our homes, making our guitars go nuts!
These days, nearly all of the guitar companies use at least some kiln-dried wood in their instruments, and this is dried to a moisture content they believe to be ideal. Unfortunately, this "ideal" is seldom approached in our homes, so our guitars dry out, and start changing, usually not for the better! Sometimes all that happens is that the frets "grow" (really the fingerboard shrinks, exposing the sharp ends of the frets), but the most common thing is a change in the action (string height). In electrics, this can be higher, or lower, depending on the moisture level of the neck vs. that of the fingerboard. In acoustics, it's almost always lower, with the notes from the 10th, through 15th frets sounding "buzzy", "tinky", or even disappearing entirely! This is because as the face of the guitar shrinks, it loses it's arch (that's right, it's not really flat), and the strings get lower, while the neck block, a fairly massive piece by guitar standards, shrinks much less, causing a "hump" in the fingerboard. Left untreated, it is possible that the top, or face may even crack in extreme cases!
Sadly, this is NOT considered to be a defect by most guitar makers. They feel that it's your fault if you don't store your instrument in a "proper" environment, that is, one with enough moisture to prevent damage.
Happily, there's something you can do to prevent the problem, and it's easy, and inexpensive. Just get, and use, a guitar humidifier. They come in different brands, shapes, and sizes, but they all work about the same way. They have a housing, and inside the housing is a sponge which you load with water. This water is gradually released into your guitar (or guitar case, depending on the model of humidifier), preventing shrinkage. Just follow the instructions that come with the humidifier, except that if you already have a problem, you may have to refill the sponge more frequently than the instructions say until the guitar comes up to a more normal humidity. Proper use of a humidifier can even reverse mild damage!
The background image is the face of one of my old guitars, notice the crack!