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MMD > Archives > January 2001 > 2001.01.17 > 06Prev  Next

Relative Humidity and the Piano
By David A. Vanderhoofven

[ Karl Ellison wrote about the problems of low relative humidity. ]

Controlling the temperature in your home will do nothing to control the
humidity in your home.  A constant temperature does not mean that the
humidity is constant.  Leaving your heat up will not stabilize the
humidity.  But, it is better to have a constant temperature than to
continually change the thermostat up and down.

> The butt flange screws had become loose, allowing the hammers to sway.

Regular maintenance of a piano involves periodic tightening of all of
the action screws.  A brand new piano should have all action screws
tightened as a part of dealer prep.  In six months to a year, all
action screws should be tightened again.  After this, the action screws
should be tightened every few years, or as necessary.  There are screws
holding the hammer flanges, wippen flanges and damper flanges.

The screw becomes loose not because it physically turns in the hole.
The screw becomes loose because the wood of the flange expands and
contracts due to humidity changes.  If the screw is tight and the wood
expands due to more moisture, the flange is now pushing against the
underside of the head of the screw.  The wood deforms and crushes, and
now the screw is loose because of "compression set".

Tightening the screw will prevent the action parts from moving from
side to side, but will not correct poor spacing of hammers and other
action parts.  The hammers must be carefully aligned with the strings
so that the hammer is striking the strings squarely.  This spacing is
done by loosening the screw, gently shifting the flange over to the
correct position, and retightening the screw.

However, if the hammer has been misshapen or deformed because of
excessive wear, the hammers must be filed correctly before spacing the
hammers to the strings.  Even if the hammer is spaced to the strings
correctly, if the grooves in the hammer do not PRECISELY line up with
the strings, the hammer will tend to shift over to the old string
grooves each time the note is played.  It can result in damage to the
action centers due to twisting of the hammer and shank.

When your home returns to 80% to 90% RH in the summer, do not be too
surprised when your piano rusts out in a few years.  Loose action
screws are the least of your worries.  If your home is going from 25%
RH to 90% RH  every year, don't be too surprised when the pinblock gets
damaged and the piano won't hold a tuning.  Don't be too surprised when
the soundboard cracks, the ribs start separating and the soundboard
buzzes and comes unglued from the rim.  Don't be too surprised when the
action warps and all the hammer heads get loose as the glue joints

> ... the Steinway people say 68-72 degrees F., at 40-60% humidity,
> is required to be compliant with their guarantee.  Wow -- I can
> just picture my electric meter grinning if I tried that!

Please send us a picture of your grinning electric meter!

If you want higher humidity indoors in the winter time, turn your heat
down, not up.  If you turn your heat up, the humidity will drop.  As
you take cold outside air in and warm it up, you reduce the amount of
moisture the air can hold.  As the Relative Humidity goes down, the air
will suck moisture out of the piano causing it to dry out.

45% RH would be an ideal environment for a piano.  An acceptable level
is between 40% RH and 50% RH.  35% RH and below is too dry.  60% RH is
too high, and eventually rust will form on the strings and tuning pins.

Many, if not all, piano manufacturers do not cover warranty claims
related to humidity induced damage.  If the climate is outside of the
limits set by the manufacturer, the warranty will be void.

Your options for controlling humidity are as follows:

1.  Control the whole house with humidifiers and dehumidifiers installed
on your heating and air conditioning system

2.  Use room humidifiers and dehumidifiers as needed.  However, there
is a limit as to how much moisture your home can physically hold
without damage to the structure of the home.

3.  Use a complete Dampp-Chaser Piano Life-Saver humidity control
system installed in your piano.  This must include a dehumidifier,
humidifier, and humidistat.

Do not use open containers of water inside your piano.  I have seen
too many pianos with a semi-circle of rust right above the open
container of water.

A piano without a player system would have the humidity control
equipment installed in the space where the player equipment goes.
On a grand piano the Dampp-Chaser system is installed under the
soundboard.  On an upright piano, the Dampp-Chaser system is installed
inside the bottom panel (under the keybed).

A player grand would not have any place to attach the Dampp-Chaser
humidity control system.  A player upright would require a humidity
control system to be installed in between the back posts of the piano.
There would be several smaller humidifiers and several smaller
dehumidifiers.  The humidistat controls the dehumidifiers and
humidifiers and turns them on and off as needed.  The entire back
of the piano is then covered with a cover.

If you suspect a problem with humidity, buy a hygrometer to measure
the humidity levels.  Radio Shack sells a good one for about $25.00 US.

Here is more info on humidity:

We now return you to your regular programming!

David A. Vanderhoofven - Registered Piano Technician
Joplin, Missouri, USA

(Message sent Wed 17 Jan 2001, 03:39:51 GMT, from time zone GMT-0600.)

Key Words in Subject:  Humidity, Piano, Relative

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