What does a piano have to do with the climate? Everything! Well, sort of.
Your piano is made up of thousands of parts, many of them wood and wool felt. Both wood and wool react to changes in air humidity levels. Their reactions to changing humidity levels
in your home mean lots of changes that occur in your piano. In order for your piano to function at its best, and to preserve the integrity and quality of your piano over the long haul, it's best to try to keep humidity levels as constant as possible throughout the year. In the climate we face in Michigan, that can be a challenge. Please read on for a solution.
One of the most vital pieces of wooden real estate in your piano is the soundboard. Piano soundboards are generally made of thin sheets of wood - most commonly certain varieties of spruce. A piano soundboard is not perfectly flat - instead, it's slightly arched. Think of a very very very gentle rise from the edges to the middle. Attached to the soundboard is the bridge - a sturdy strip of wood, over which the piano's strings are held in place under high tension. So, the strings press down on the bridge, and the bridge presses down on the slightly arched soundboard.
When the air around the soundboard has more moisture, such as in the higher humidity times of summer, the soundboard absorbs water and swells up. The soundboard's arch rises, and that pushes up the bridge and the strings, and that causes the string tension to rise, which causes the strings to produce higher pitched sounds when struck by the hammers. This phenomenon is most pronounced in the middle of the piano, in the region around middle C, and tapering off as you go towards the bass and treble regions. You tend to have notes in the middle of your piano that go most sharp in this situation.
In times of lower humidity, such as the winter, when we're heating our homes with warm, dry air, the soundboard loses water and shrinks, causing the arch to go down, lowering the bridge, lowering the tension on the strings, and causing the strings to produce lower pitched sounds. The piano goes flat in this scenario.
Imagine what these seasonal humidity variations tend to do to your piano's tuning.
In addition, your piano has many other wood and wool parts that also swell and shrink with the rise and fall of humidity levels. In times of high humidity, your piano's keys might stick or move sluggishly. Hammers might rub against each other and interfere with playing. In times of low humidity, wood and felt parts that were swollen in summer now shrink, possibly becoming loose when these are supposed to hold firm. (Cats and cat hair can also have effects on piano performance.)
One way to reduce the seasonal variations in humidity is to place a mechanism near your piano's soundboard that creates a microclimate that keeps within a specified range of relative humidity - generally between approximately 35% and 50% relative humidity. In upright pianos, especially, these systems keep the humidity level in this range for most of the piano's wood and wool parts, because the mechanism is enclosed in the piano. In grand pianos, the mechanism is placed under the soundboard, and is exposed to the air. If you're not quite getting the results you want in your grand piano, we can add a semi-permeable undercover that acts to shelter the humidity microclimate from outside air.
The system is called the Piano Life Saver System, manufactured in the United States by Dampp-Chaser Corporation, a company that has been in the business since 1947. I am a certified installer of these systems. Please let me know if you would like more information about the system for your piano.