When moving a fine acoustic guitar from a freezing outside temperature to a heated building, thermal shock can cause its nitrocellulose finish to crack or check. To avoid this, keep the case closed for a few hours to let the instrument acclimate before pulling it out. Photo by Richard Hoover

If you choose an added-water system, like the Oasis OH-1 or D’Addario Planet Waves Humidifier, you can be sure their designers have taken care to make their products leak-resistant. That said, to keep it working correctly, you’ll need to stay vigilant and monitor the frequency and amount of water needed for refills. Avoid any system that may bring your instrument in direct contact with wetness. It’s much better to strategically place a device per the manufacturer’s recommendation than to indiscriminately toss something into the case.

An important caveat with these types of humidifiers: They only hydrate, they do not dehumidify! Do not use them when your environment is already over your humidity target, as excess humidity can delaminate critical glue joints and warp components critical to playability.

How often you check water level depends on your situation. Our pal Larry Broido, of the late, great Acoustic Roots guitar shop in Philadelphia, found it necessary to put 10 gallons of water per day through his humidifiers to maintain his 2,500 square-foot shop at above 40 percent RH during the driest winter months. So the homemade perforated soap dish with a sponge in it may not emit enough moisture—no matter how often you dunk it. Better to invest in a commercially made device with adequate capacity for your conditions.

If you got off cheap when buying your guitar, you need to be less concerned about seasonal- and age-related changes because, like patio furniture, your instrument was designed to weather well.

Case Closed
As I mentioned earlier, keeping your precious guitar in its case is one of the best ways to limit exposure to rapid temperature changes. But you still have to exercise common sense: When a guitar with a nitrocellulose finish moves from a freezing outside temperature to a heated building, its finish can crack from thermal shock if you open the case suddenly. To avoid this, keep the case closed and move it away from any heat source for a few hours. In other words, let your instrument acclimate before pulling it out.

Within hours, a guitar in a black case in direct sunlight can reach interior temperatures hot enough to re-plasticize glues and cause components to creep. The same horrors can occur in a closed car, which can quickly reach 160 to 180 degrees F on a hot day. If you’re heading into a situation where these conditions are unavoidable, prepare by slackening the strings a half-step, maintaining just enough tension to keep the nut and bridge pins in place. Put the guitar in its case and then cover it with clothes or towels for insulation. Park in the shade and crack the windows, and then deal quickly with whatever distractions caused you to take this risk in the first place.

When your guitar has cooled down from this kind of exposure and you tune it back to pitch, it may take a little time for the neck to return to the same amount of relief that the adjustable truss rod had been set to before you detuned the instrument. Don’t be tempted to adjust the rod or change your action height at this point. Before considering corrective adjustments, give the guitar a day under normal temperature conditions and string tension to return to your default settings.

A digital hygrometer is an essential tool for monitoring the moisture levels in the air, both in the factory and, ultimately, in the future owner’s home. Photo by Richard Hoover

Be Mindful
In review, wet or dry or hot are bad for your acoustic guitar. Wet and hot equals steam, which can turn your guitar into a kit that needs reassembly. Exceedingly dry conditions can cause wood to crack and components to warp. The more expensive the guitar, the more it demands that attention be given to the above precautions. You can find a thoughtful treatise on proper care for your acoustic, as well as how to readjust your guitar to correct for environmental insult, on the Santa Cruz Guitar Company website.

The bottom line: It doesn’t take inordinate work to care for your guitar, but it does require commitment. However, if you make the effort—and modest investment—you’ll be rewarded with an instrument that will play and sound at its best.