[CAUT] Re: Temperature and pitch

[James Ellis]

Guy, Let me say it a different way, and perhaps that will clear up the
confusion.  I certainly don't want to mislead anyone.

Let's assume the piano is stable at a reasonable room temperature and
relative humidity, and the temperature is the same throughout the piano,
and does not change while you are tuning:

1.  The temperature rapidly drops.  The strings cool faster than the plate,
and the piano goes sharp and out of tune because the strings did not all
cool by the same amount.

2.  The piano sits at the new temperature for 24 hours.  It will be back in
fairly good tune - not as good as it was before, but not bad either.

3.  The temperature suddenly rises to its original setting, and the piano
goes flat and out of tune.

4.  The temperature stays at its original setting for 24 hours, and the
piano will almost be back where it was before - not perfectly - but very
close.

5.  The temperature takes another abrupt rise, and goes above its original
setting, and the piano goes flat again and out of tune.

6.  The temp stays at the elevated setting for another 24 hours, and the
piano will be in fairly good tune again, and almost on pitch.

7.  The temp suddenly drops back to its original setting, and the piano
goes sharp again.

8.  The temp stays at the original setting for 24 hours, and the piano is
almost back on pitch again, and almost in tune, but now it's ready for
another tuning.

All the temperature ups and downs have had their effect on the relative
humidity, and this has taken its toll on the soundboard.  It has also
worked on the various parts of the piano that don't all have the same
temperature coefficient.  All the while, the thing has been under tension.
And every time things moved at the bridge, tuning pins, etc, etc, it
actually slipped, and never quite came back to the same place as it was
before.

On the other hand, if you tune the piano while the temperature is changing,
you are going to end up with a botched tuning, especially if you are tuning
with an ETD.

Does this answer your question?  If not, I'll try again.

Sincerely, Jim Ellis

At 08:30 AM 3/3/05 -0700, Nichols wrote:
> At 05:50 PM 3/2/2005 -0500, you wrote:
>   
>
> The strings go sharp when they are cooler than the plate, and flat when
>  I happens fast - a matter of a very few
>  If the piano has been
> subjected to a major temperature change, wait a few hours until everything
> in the piano has come to the same tempterture, and it should be back on
>  The cast iron plate and the steel strings have similar temperature
> coefficients.
>
> Jim Ellis
>
> Jim,
>   From the department of redundancy department, here we are again on this
>subject. Back on Feb. twenty-tooth, (subject: Mind-Bender),  I was confused
>about one of your statements and I am still perplexed. I hope you can find
>time to help my two remaining brain cells understand what you mean when you
>say:
>
>" If the piano has been
> subjected to a major temperature change, wait a few hours until everything
>"
>
> Are you saying that if everything in the piano reaches the same
>temperature, even if that is a different temperature than where it
>started,"" change, when the piano returns to it's original temperature it
>will be back on pitch?
>
> Respectfully,
> Guy Nichols, RPT
>