Your piano is made primarily of wood, a versatile and beautiful material that is ideal for piano construction. However, because it's made of wood, your piano can be affected by humidity. Seasonal and even daily changes in humidity can cause wood parts to swell and shrink, affecting tuning stability and touch.
How does the humidity level affect your piano's tuning?
Swelling and shrinking of the piano's soundboard is the most immediate and noticeable effect of humidity changes. As the moisture level in the soundboard increases during periods of high humidity, the crown expands and pushes the bridge harder against the strings. The strings are stretched tighter, and the piano's pitch rises. During periods of low humidity the soundboard shrinks, reducing the crown and decreasing pressure against the strings causing the pitch to drop. A piano only will stay in tune as long as the humidity level is consistent.
Other materials in your piano also are affected by changes the changes in humidity. The felt and leather parts in your piano's action can change dimension, affecting regulation and friction, or stiffness of the touch. Very high humidity can create condensation on metal parts such as strings, tuning pins and hardware, eventually causing them to rust.
Protecting your piano from humidity fluctuations should be part of your regular piano maintenance program. Keeping humidity as well as temperature levels as consistent as possible will help keep it in tune longer and guard against soundboard cracks, loose tuning pins, and glue joint problems.
How can you protect your piano against the effects of humidity fluctuations?
Position your piano away from areas where it would be exposed to extreme temperatures and humidity levels such as heating and cooling vents, doors, windows and direct sunlight. If your home is not well insulated, position your piano on an interior wall rather than an outside wall.
Have a humidity control system installed in your piano. These systems consist of three parts: a humidifier for adding moisture to the air, a dehumidifier for eliminating excess moisture, and a humidistat or control unit which senses the humidity of the air within the piano and activates the system to add or remove moisture as needed. The components are installed out of sight, they are easy to maintain and can be installed by your piano technician.
It's important to remember that controlling the humidity will not eliminate the need for regular tunings or other types of maintenance, but will allow for more stable tunings by reducing the radical changes your piano may experience through the seasons. When your piano stays closer to its correct pitch level, your technician doesn't have to perform a significant pitch adjustment before the tuning. A stable environment will go a long way in preserving your piano through the years, giving you and your family a lifetime of enjoyment.