Humidity Control

How does humidity level affect my piano's tuning?

Swelling and shrinking of the piano's soundboard is the most immediate and noticeable effect of humidity change. As the moisture level in the soundboard increases during periods of high relative humidity, the crown expands and pushes the bridge harder against the strings. The strings are stretched tighter and the piano's pitch rises. Because this increase in crown is greater in the center of the soundboard than at the edges, the pitch rises more in the middle octaves than in the bass or treble registers.

During periods of low relative humidity (winter) the soundboard shrinks, reducing the crown and decreasing pressure against the strings. The pitch drops, again with the greatest effect noticeable in the center of the keyboard. When relative humidity returns to its previous level, the average pitch of all the strings will return to normal, although the exact pitch of individual strings will be slightly changed from their original settings. Thus, a piano only will stay in tune as long as the relative humidity level in the air surrounding the soundboard remains constant. Extreme humidity changes require making greater changes in string tension to bring the piano into tune. This upsets the equilibrium between the string tension and the piano frame, and the piano never becomes stable.

How will humidity control benefit my piano?

While not eliminating the need for regular piano maintenance, humidity control will allow more stable tunings by reducing the radical pitch changes your piano may experience through the seasons. When your piano stays closer to its correct pitch level of A440 (440 cycles per second), your technician does not have to perform a large pitch raising or lowering procedure prior to fine tuning. Thus, a balance of forces is maintained between the strings and the frame of the piano, allowing more accurate and stable tunings to be done.

In addition, a stable environment will help to preserve your piano through the years. Wood parts, glue joints, metal parts and your piano's finish will all last longer if not subjected to excessive humidity swings. Maintaining the correct environment will help prevent problems like sticking keys, loose tuning pins, rusty strings and will preserve your piano investment for a lifetime of enjoyment.

What is the best way to control the humidity in my piano?

One of the most effective and least expensive ways of controlling the humidity in and around your piano is through a Dampp-Chaser® Climate Control System. This system consists of three basic components that work together to maintain the recommended average 42% relative humidity throughout the changing seasons. The humidifier tank contains water that is absorbed by the special wicks and converted to moisture which is released to the soundboard and other wooden and felt parts of the piano. In the humid season, the dehumidifier rod (or rods, in the case of grands) work to dispel the excessive moisture that is in the air. These two components are controlled by a humidistat which is factory set at 42%, and cycles back and forth between the two other components as the humidity rises or falls from that setting.

 This system is designed to be efficient and easy to maintain (water must be added to the tank through a special tubing and pitcher system as required). Talk to your piano technician about it, and he can recommend the exact type of installation that will work best for your particular piano and home environment.

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