Grand Piano

[grandpiano]

The most important thing to remember when discussing care and maintenance of pianos is that the instruments are made primarily of wood. Just like a sponge, wood expands when the humidity goes up and contracts when the humidity goes down. This said, pianos live and die by changes of humidity. In the short term, fluctuations in humidity throw a piano out of tune. In the long term, years of fluctuations cause structural damage ending with the piano being useless as an instrument.
In grand pianos, the frame and strings are horizontal, with the strings extending away from the keyboard. There are several sizes of grand piano. A rough generalization distinguishes the "concert grand" (between about 2.2 m and 3 m long) from the "parlor grand" or "boudoir grand" (about 1.7 m to 2.2 m) and the smaller "baby grand".

[Bill Kibby]

This is a Piano History forum, and not really the place for discussing atmospheric effects.

It is certainly NOT the place to advertse your wares free.

I would have to add that although fluctuations in air humidity do cause fluctuations in the wood's own water content, it is the raising of temperatures to a point where the resin evaporates which causes most of the major structural damage, because once the resin is gone, it cannot be replaced.