Managing the Humidity Level of Your Instrument is a Matter of Balance

By Elizabeth Marshall

Though musicians are taught to keep a violin, viola, cello, or double bass properly humidified during the dry winter season, over-doing it with the humidifier can create a different—and occasionally grosser—set of problems for string players. Finding the right balance between too much and too little humidity isn’t difficult to manage, but a few telltale signs will let you know when you’ve gone too far in one direction or the other.

While dry air from indoor heaters keeps many string players focused on properly humidifying their instruments and bows, depending on your region and the relative humidity of your surroundings, a humidifying system may not be necessary for daily use. The ideal relative humidity range for a stringed instrument and its bow is somewhere in the neighborhood of 40–60 percent, and depending the system of cooling and heating in your home, a dehumidifier might actually be necessary to maintain a healthy instrument.

A reader recently wrote Strings to describe how a teacher threw away a moldy case humidifier that the student’s mother dutifully filled every day and left in the case. Though tossing the humidifier may have been a bold move on the teacher’s part, he wasn’t necessarily wrong to take such a definitive action against mold—it can be a real health issue for you and for your violin. Because many of the commonly used humidifiers are relatively inexpensive, they’re easily replaceable and should be tossed out if mold is suspected.


Too Much Humidity

Exposure to too much humidity can affect your instrument in other ways as well, and may even make the wood swell. When this happens, the soundpost can lose its footing inside the instrument, giving you a mushy, flabby sound. Overall, in an environment that is too humid, the instrument and bow will become sluggish and uncomfortable to play. Excess humidity can also cause the seams of an instrument to open, which is not a major repair issue, but will necessitate a trip to the violin shop. And as people who live in tropical locations might know, in extreme cases, the wood of a violin can start to warp if exposed to sustained, unrelenting moisture. It would take a very high relative humidity to cause this to happen, but it is not unheard of.

Too Little Humidity

Naturally, too little humidity is also a problem and an instrument that’s too dry will exhibit several telltale symptoms. As the wood shrinks along the grain, the instrument will compress slightly, and the soundpost may become too rigid. This will leave the instrument feeling “tight” under the hands of a player, driving you to feel the need to “dig in” more than usual to pull a sound from the instrument. The reaction time of the sound itself will become sluggish and, at times, scratchy and harsh. In essence, the entire system is under stress and the action under both hands is stiff and unyielding. In more dire circumstances of dryness, cracks can form in the body of an instrument, causing hundreds, if not thousands of dollars in repairs.

Finding a Balance

One way to avoid the issue of uncontrolled humidity is to invest in a hygrometer. Hygrometers are small instruments used to measure the humidity in the atmosphere and often come as a feature on many cases. Knowing what is happening in your case is half the battle. There are a number of case humidifiers on the market: choose one and apply as your hygrometer indicates.


If this feels too fussy, there are also two-way humidity control systems for cases available, which will either absorb or release moisture into the case as they detect the humidity levels straying beyond the ideal range. Certainly a low-maintenance solution.

Don’t Ignore Your Bow

Keeping this in mind, it’s also a good idea to keep an eye on the hair on your bow. As the humidity becomes too scant, the hair will shrink and you will need to loosen your bow as you play. The opposite is true for too much moisture in the air; the hair will stretch and you will feel like you constantly have to tighten your bow to get a comfortable tension on the stick.


By maintaining a steady humidity in the 40–60 percent range, issues like a poor-playing instrument, a stretchy bow, and moldy humidifiers can be a thing of the past.

A version of this article first ran in the March 2015 issue of Strings.

Want more instrument and bow care? Try Strings’ Violin Owner’s Manual. We also offer a handy series of web guides: Care & Repair of Violins or Violas, Caring for Your Violin or Viola Bow, Care & Repair of Cellos, and Caring for Your Cello Bow.