Can Humidity damage my piano?

Hello Piano Players and music lovers.  This blog is about the effects of  Humidity, the lack of enough humidity, and the changes in Humidity on a piano.

High Humidity

High humidity does two things to a piano.  Its causes rust and causes the wood to swell.   The Main parts rust affects on a piano is the strings.   The tone is affected by rust on the strings.  This happens usually in pianos subjected to a lot of high humidity.   It is also common on old pianos.   Rust on strings also causes what is called false beats.  This is where one  string sounds like it is out of tune.  This will affect the higher strings more though it can affect the middle of the piano.   When tuning a piano like this we can make this problem a little better by using phase cancellation.  If the high end of your piano sounds like it is not in tune as well as the rest of the piano right after a tuning,  this is why.   Note:  right after tuning.  The high end usually is the first part to go out of tune because the strings are shorter.

Tuning Pins rust.  This doesn’t affect the piano it just doesn’t look good.

Key Pins can rust and cause Keys to stick.  I have only seen this on very old pianos or pianos that have been subjected to very high humidity.  Like left on the front porch or in damp conditions.

Now on to wood swelling.

Wood swelling is common in causing keys to stick.  There are a lot of working wood and felt parts activated when a key is pressed.   Instead of giving you a lot of piano terms like action centers, key bushings, balance rail holes and explaining what they are I will just leave it at that.  Most sticking keys are easy to fix but when you have a bunch of sticking keys from high humidity it can get labor extensive.

The soundboard also swells in High humidity but we will talk about that in changes in Humidity.

Low Humidity

Wood contracts in Low Humidity.  This is why you may see more space between your boards on your wood deck outside in the winter time.   On a piano this means cracks.  Cracks in the soundboard and cracks in the bass bridge are not uncommon in older pianos subjected to low humidity.   Both of these problems can cause tuning instability.  Low Humidity also causes wobbly keys and wobbly action parts like hammers.

I see a lot of pianos that have a dehumidifier rod installed in the piano but no Humidistat(a humidistat works like a thermostat it tells the dehumidifier to cut off when the humidity is too low).   This keeps the humidity away and in seasons with high humidity its ok but in seasons of low humidity it brings the humidity too low.  I frequently see cracks in the bass bridge in a piano with a dehumidifier rod but no humidistat.   This is because most technicians today no not to install a dehumidifier rod without a humidistat but it was common years ago.  So when I see a dehumidifier without the humidistat I know it has been in there a while.  Best hope is that it has been unplugged most of the time.  So if you have a dehumidifier rod in your piano without a humidistat I recommend getting a Humidistat installed.  If not I would unplug the dehumidifier.   If you recently had the piano tuned wait 6 months.

If you have a dehumidifier in your piano without a humidistat then I recommend getting a humidistat installed.  If you dont want to get a humidistat then I would recommend unplugging the dehumidifier rod.

Changes in Humidity

A change in humidity will throw a piano out of tune.   I dont mean a change from day to day.  It takes about 3 weeks for the wood to fully adjust to a different humidity level.   So if you had your piano tuned in the winter and now it is Summer your piano could very well be sharp.  This past year summer(2015) Most pianos that I tuned that were previously tuned in the winter were very sharp. (except those that had a humidity control system).    The opposite happens if you had your piano tuned in the summer.  In the winter it is flat.  This is why we suggest getting a tuning every 6 months for most pianos.  The less overall tension change I have to do when tuning the more stable the tuning will be.

Changes in humidity also causes loose tuning pins.  The tuning pins are what we are turning with our tuning hammer to adjust the string tension.   The tuning pins are driven in wood.  The string tension on the tuning pin pulls downward(or towards the back of the piano on a grand).   Through changes in humidity the pins move up and down a little causing loose pins after a while.

Humidity control systems are a great investment for any piano you plan on keeping and especially for new or newer pianos.  It keeps your piano in tune longer so for most piano use it pays for itself  by not having to get tunings as frequent( If you play a lot and/or hard you will still need frequent tunings but it will help it stay in tune better).  It also extends the life of your piano and the quality of sound coming from it.

Thank you for reading my blog

Tyner’s Piano