We who heat our homes in cold weather face the effects of extreme
dryness.  I wish that I had a good answer to this problem.  Unless one
lives in a museum with climate control, we will always be plagued with
variations in humidity.

As I mentioned last year, I  made some humidifiers from quart pop
bottles with cloth wicks.(or quart canning jars)   These are placed
between each post in the back of the upright piano, and the entire back
of the piano is covered with a piece of thin plastic sheeting and
sealed around the edges with tape.  Several of the bottles with wicks
are placed inside the bottom of the piano, and the piano covers kept
closed until it is in use.  The pop bottles give off some gentle
humidification.  (This method would have to be modified for a grand
piano.)

The bottles should be checked every week or so to be sure that they
have enough water and none have started to mold.  If mold is found, the
bottle and wick should be removed and washed in chorine bleach, rinsed
and replaced.  It is also a good idea to place a humidity gauge within
the piano and monitor it carefully.

I have always felt that humidity should be equal on each side of a
sound board, be it using the dehumidifying heat rods in summer, or
adding moisture in winter via the bottle and wick method.  I have seen
some electrical devices placed under grand piano sound boards that emit
moisture, but this moisture is only emitted on one side of the sound
board.  I feel that this could be more damaging to a sound board than
no humidity at all.

I have not experienced any rusting, using the pop bottles and feel that
even with them, there is really not enough humidity to do any harm, yet
better than no humidity at all.

Another idea would be to build a large tent of plastic sheeting to
surround the piano, and place an automatic humidifier inside the tent,
and keep the humidity at the correct percentage.  I have not tried
this, but think that it might work.  I am sure that many wives would
object to the looks of one of these contraptions set up in their living
room!

The worst problem with household humidifiers are the damage they can
create to your home, especially if your home is old and not properly
ventilated and insulated.  While one can get household humidifiers to
produce the correct humidity throughout the house, some of this
humidity can get trapped inside the walls of your home and reduce the
efficiency of insulation.

If one is not careful, water in humidifiers can become laden with
bacteria and mold, which in turn is atomized into the air in your home.
Mineral buildup from hard water is also a problem.  In addition, the
humid air can start saturating sheet rock, and also get behind the
external paint of your house and suddenly the paint will start peeling,
and you have produced an additional expensive problem.

By the same token, if the humidity goes up to 90% in summer you need
to temper that too, by using the gentle heat rods designed for lowering
humidity.  Again, one placed on each side of the sound board.

Bruce Clark