strict temperature effects

[Travis Gordy]

Jim:  My response does not answer your question directly but my experience
of tuning a S&S L in a modern home, large room, vaulted ceiling and
skylight on a bright day may be of some interest.  The owner, a piano
teacher, kept the piano top proped to its highest position. When I started
tuning the sunlight through the skylight  was not shining directly on the
piano.  I was not even aware of where it was shining.  But after setting
the temperament and going a ways up the scale the temperament area went
out.  The sun had moved to be shining directly on the bridge and plate in
the center of the piano.  I do not remember if it went sharp or flat, but I
assume the effect on pitch was caused by increased plate and string
temperature and not on moisture content change of the soundboard for which
there  was not enough time and the area of direct sun was small.  I would
guess the temperament went flat.

I showed and explained the situation to the owner and suggested she find a
better location for the piano and leave the top down. I know she did
neither.  Go figure.

Travis Gordy, RPT

> From: james payne <jlpayne@netw.com>
> To: pianotech@ptg.org
> Subject: strict temperature effects
> Date: Wednesday, March 11, 1998 10:02 AM
> 
> Can anyone help me with a little research project I am pursuing? I am
> trying to figure out the effect of temperature changes on the pitch of a
> piano. We know that changing the temperature of the air will normally
> change its relative humidity, hence the moisture content of the
soundboard,
> and hence pitch. My question is, if relative humidity were kept constant
so
> that no soundboard changes occurred, what happens to the pitch of a piano
> when its temperature is raised? Does it go sharp, or flat, or not change?
> I’d be happy to hear about a) any speculations or theories; b) any
> empirical data or experiences; c) anything written on the subject.
Thanks.
> Jim Payne, RPT Sandpoint, Idaho: jlpayne@netw.com
>