For many varied instruments—such as guitars, violins, and clarinets—builders are hard pressed to find a better sounding and feeling material than wood. There’s a certain intangible organic quality to the sound produced from fine wooden instruments that can’t yet be matched by synthetic materials.

With this wonderfully woody tone comes a catch: wood is an organic material, and even after it has been harvested, cured, and transformed into your instrument, the cells continue to absorb and release moisture. In order to keep your finely built wooden acoustic instrument playing and sounding its best, it’s important to control the moisture in the wood.

Dangers of High Humidity

As wood absorbs moisture, it swells, becomes heavier, and expands. Dangers of high humidity include glue joints coming undone and permanent warping. Signs that your stringed instrument is swelling may begin with higher than normal string height, because as the top is rising and swelling up, it lifts the bridge, which makes your instrument difficult to play. Woodwind instruments play out of tune and reeds become saturated and difficult to play.

A dry instrument is far worse than a moist one. When moisture is sucked out of the wood, it is left brittle and can easily crack. This is especially true for finely built acoustic instruments. For example, with a string instrument, the wood will shrink, causing the top and back to concave and eventually crack from the pressure of pulling against the braces.

One indicator that a string instrument is losing moisture begins with buzzing notes, caused by the top caving down and lowering the action. On guitars, you may notice sharp fret ends sticking out from the sides of the neck as the fingerboard shrinks. While more resistant to cracking than stringed instruments, woodwinds are also susceptible to dry weather.

To understand the effects of arid climates on acoustic instruments, check out Humidity 101 on the Taylor Guitar website.

Controlling the Weather

In the factory or custom shop, your instrument was built in a specific climate. In order to play its best and remain within factory tolerances, the humidity needs to remain the same. Ideally, this is around 45% to 55% humidity.

A hygrometer can tell you the relative humidity of your home or instrument case. Keep one in the room where you store your instruments so you can take appropriate action in keeping constant 45% to 55% humidity year round. You can buy both analog and digital hygrometers, and some instrument cases come with one built in. Here are several ways you can control humidity:

• Air conditioning: Along with having a cooling effect, air conditioners also dehumidify the air. If you have central AC, you’ll be in great shape for those muggy summer months. Window units are a less expensive option, and with careful monitoring of your hygrometer, you will be able to maintain the optimum humidity.
• Dehumidifiers: Dehumidifiers are a little cheaper to run than AC units, but they don’t cool the room. Also, unlike an AC unit, you will need to periodically empty the water that is collected from the air.
• Central humidifier: If your home has central heating and cooling, for several hundred dollars you can add on a humidifier to keep your entire home at a constant, healthy humidity. Whole home humidifiers require no maintenance or special attention, and they allow you to leave instruments anywhere in the house, even out of their cases, if you wish.
• Portable room humidifiers: The next best option to a central humidifier is to control the humidity in the room where you keep your instruments. A good room humidifier costs around $100, is light, portable, and simple to use. Unlike a central unit, however, you will need to clean it and add water every few days or so.
• Case humidifiers: Even if you have a central or room humidifier, it’s still a good idea to have a case humidifier. There are many on the market, the simplest being a rubber tube with a sponge inside. These humidifiers control the environment inside the case, so no matter where you go, you can be sure that your instrument is not drying out.

While these are the least expensive solutions, they require the most attention. If you have a room full of instruments, you’ll need to check each one every day. Also, they are ineffective while your instrument is out of the case.

Check out these products for controlling the humidity of instruments:

Humicase Humidification Kit

The Humicase Humidification Kit has two humidification units that easily install in an instrument case, a digital hygro-thermometer to monitor humidity and temperature, and an eight-ounce bottle of activation solution. The humidifying units contain a compound that, when activated by the solution, let off a constant and measured amount of moisture for three to six months. As the humidity drops, simply add distilled water.

Planet Waves Humidipak

This is a great option for places that have both wet and dry seasons. The Humidipak is a pouch that fits in the sound hole of a guitar and contains two replaceable packets with a humidity absorbing and releasing gel. No matter what the climate is, the Humidipak either absorbs or releases moisture to maintain constant 45% to 55% humidity. The packs will last at least two months, depending on the climate.

DampIt

DampIts are a classic solution to maintain moisture. They are simple rubber tubes with holes, stuffed with a sponge. You must periodically wet them and then place them in the sound hole of your instrument. Though they require some guesswork and a close watch on your hygrometer, Dampits are an effective method of keeping a variety of wooden instruments healthy in dry winters and desert summers.