Dean Mermell is concerned about moving his Mason & Hamlin Ampico to
the desert where his piano will encounter a very dry climate [150205
MMDigest].  I would be concerned too.  I have written several articles
on the effects of drastic changes in humidity.

I live on a lake.  In summer the relative humidity can reach upward
to 85% or more, but in winter during the heating season, the relative
humidity dips to about 15%.  It is these drastic fluctuations of the
percentage of humidity that can rapidly and greatly damage a piano.
Here, in central New York State, my house is very old.  Using a
humidifier during the heating season can do more harm than good.

When humidifiers first became popular, I thought a humidifier was the
answer.  For the first time, I was able to bring the humidity inside my
house up to 40%.  For awhile my Ampico piano seemed to be doing well,
and I thought it was beneficial.

However, during this time there were other things happening that I was
not aware of; when I discovered the consequences, it was too late.
Mold began to accumulate in an unheated upstairs room.  Moisture formed
on the cold windows and began rotting the window sills.  Everything in
the attic became soaking wet.  The Christmas decorations were ruined.
The sheet rock ceiling in the upstairs hallway began to sag and fall
down.  By spring the exterior paint on the house began to blister and
peel.  I learned the hard way!

In summer I could isolate the piano in the living room, by shutting
doors and windows, and running a de-humidifier to keep the relative
humidity at 35%.  However, in winter I had no way of humidifying
the room without suffering the consequences.  To solve this problem,
I constructed a plastic tent over the piano, and keep pans of water
on the floor under the plastic tent filled with water.  It is rather
unsightly, but the piano stays in tune, and the sound board is safe
from becoming too dry.

I am reluctant to use commercial piano attachments that are supposed to
automatically humidify or de-humidify with automatic settings because
they only add or subtract moisture from one side of the sound board.
Logic teaches us if we add moisture to one side of a piece of wood when
the other side is very dry, the wood will warp, and possibly split.
That is my reason for the tent and equal distribution of moisture.

Bruce Clark