Humidity Control

Controlling humidity in the air around your piano is the key to making tunings last and the key to extending your instrument’s useful life. Short lived tunings, sticking keys, sluggish action, lifting veneer, rusty strings, rattles, clicks and squeaks are all common problems that are caused by uncontrolled humidity changes. I often comment to my customers that I am in a constant battle with humidity, but it is what keeps me in business.

Pianos are primarily made of wood. Wood is hydroscopic (absorbing or desorbing moisture depending on the humidity level of the surrounding air). Changes in relative humidity cause the wooden parts (especially the soundboard) to swell or shrink. When this happens the tension on the strings changes and the tuning is affected.

What is relative humidity? It is the percentage of moisture in the air compared to the maximum amount of moisture that the air can hold at a given temperature. Warmer air can hold more moisture then cooler air. If you take warm humid air and lower its temperature enough, you will reach a point where it cannot hold any more moisture. It is at 100% relative humidity and any further cooling will cause some of the water vapor to condense.

In New England we have humid summers and dry winters. Summer humidity can be as high as 80% and winter heating can bring it to as low as 12%. The ideal humidity for a piano is 42% relative. The temperature around a piano can change and not wreck the tuning if the relative humidity stays the same. However, if the temperature stays the same, but the relative humidity changes, the tuning will be affected.

So what is a piano owner to do? The first step is determining what is happening around your piano. I strongly recommend using a gauge to track the humidity swings around your piano. Hardware stores, electronic stores, Brookstone and even your piano technician can obtain these for you. (Typically, a good humidity gauge costs between $25 and $75. You might find that one spot in a room is more stable then the rest of the room.)

It is generally not possible to control the air in a room to a year-round 42%. But by running a room humidifier in the winter, you might raise the relative humidity to 30%. If you run a dehumidifier or air conditioner in the summer, you might lower the relative humidity to 60%. Doing this reduces the wide swing of 12% to 80% to a gentler 30% to 60%. However, it is best for your piano, and easier on you, if you simply concern yourself with the humidity around the piano.

It is possible to micro manage the humidity in and immediately around a piano by having a Dampp-Chaser Climate Control System installed in your piano. A Dampp-Chaser is a device that raises or lowers the humidity depending on what is needed. A humidifier tank adds moisture when needed, and a dehumidifier rod lowers the humidity by raising the air temperature slightly without adding moisture. A humidistat constantly monitors the humidity level and switches on whichever portion of the system is needed. The system maintains a year round 42% relative humidity level.

Over the past 25 years, I have installed over 100 Dampp-Chaser systems. Pianos with these systems consistently hold tunings better than they did prior to having the systems installed. Less change means longer life. For more information on this product, please look at the Dampp-Chaser web site ( or contact Gordon.


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