Humidity and Wooden Stringed Instruments
Stringed musical instruments respond to their surroundings. They are assembled from a variety of natural and man-made materials that shrink and swell in reaction to their environment. They are generally made from aged materials that are stable at 35% to 45% humidity relative to 72 degrees Fahrenheit (relative humidity). They respond drastically to radical changes in temperature or relative humidity. Basically, they are happy in spaces where you are comfortable: 35 to 60% relative humidity: 65 to 75 degrees Fahrenheit.
In general, summer weather brings higher temperatures and higher relative humidity. The instrument’s wood swells as it absorbs moisture. An early sign of trouble is high action (difficult to play). As it continues to swell the results can be pretty bad: distorted tops and backs, loosened frets, purfling separation, binding separation, brace separation, cracks around inlays – you get the picture: damage that is not covered by warrantees.
Winter weather generally means dry air. The relative humidity in New England (inside houses without humidification) can fall to 5% or 15%. An early warning sign is low action including string buzzing. If the instrument is allowed to dry out too much, the results include joint separation as the wood shrinks, finish cracks and pronounced graining of the top. In severe cases the instrument literally pulls itself apart from the stress of differential shrinkage.
Rules of Thumb:
- We strongly recommend that you get a Hygrometer: A device that reads the humidity of the air relative to temperature. These are available at our shop or other specialty stores like Radio Shack or a good hardware store. Get to know the relative humidity of the space where your instrument lives in all seasons.
- In dry weather, consider humidifying your house. If that is not possible, keep your instrument in its case with humidification. Numerous devices are available to supplement the relative humidity inside the case during dry months.
- Never leave your instrument in a car (summer or winter). The temperature extremes spell certain disaster.
- Never leave an instrument in a damp basement or warm attic – in or out of its case.
- Limit exposure to direct sunlight.
- If the case is very cold, give it time to acclimate to indoor temperature before opening it. The very thin finish of a cold instrument is likely to crack if suddenly exposed to warm air.
In general, the instrument is happy when you are comfortable but don’t trust your impressions without the benefit of an hygrometer. They are cheap insurance and your instrument is well worth protecting.