|Extreme swings from hot to cold or dry to wet are harmful
to your piano. Dryness causes the piano's pitch to go flat;
moisture makes it go sharp. Repeated swings in relative humidity
can cause sound boards to crack or distort. Extreme dryness
can also weaken the glue joints that hold the soundboard and
other wood portions of the piano together. Moisture may lead
to string rust. A piano functions best under fairly consistent
conditions which are neither too wet nor dry. Optimally at
a temperature of 68 degrees F and 42 percent relative humidity.
Using an air conditioner in humid summer months and adding
a humidifier to your central heating system will reduce the
extremes of high and low humidity. Room humidifiers and dehumidifiers,
as well as systems designed to be installed inside pianos,
will control humidity-related disorders.