Humidity of between 50% and 60% is ideal for pianos. This is because of the delicate parts made of wood, felt and cloth that are all extremely sensitive to humidity.
Too humid and the tone will become unclear, the hammers will become dull and internal parts will begin to rust. Too dry and the wooden and felt components will shrink and in some cases the soundboard, joints and other laminated parts can come apart.
Using a hygrometer will help you track the temperature and air condition of your room and ensure that the climate is ideal for your piano.
