Did you know that pianos are very sensitive to humidity changes? The most vulnerable parts of a piano are the soundboard, bridges, and pinblock. Excessive dryness can cause wood to shrink or become brittle, which can cause cracks and major tuning stability problems. Excessive moisture can cause swelling and warping, creating tuning problems as well. Moisture, particularly in the summer months, is often also the culprit for stuck keys and action sluggishness.
Relative humidity is measured with a hygrometer, or with a simple humidity monitor like this one. The optimal range for pianos (as well as other musical instruments made of wood) is 40-60%. It’s a little damp in the room right now for this piano!
You can pick up a simple humidity monitor for $10-15 that should typically be accurate within +/- 5%. If you find that the area around your piano tends to have humidity levels well above 60% or well below 40%, you should seriously consider some type of humidity control. You may want to buy a room humidifier or dehumidifier if the problem is bad enough, or otherwise consider a Dampp-Chaser Piano Lifesaver system. I’ve installed a number of these systems, and highly recommend them, particularly in churches and schools.
If you’d like to read more about humidity and its effect on pianos, visit the “Humidity Control” page.