humidity and unisons

[Newton Hunt]

>        Just one more piece of evidence to confuse and confound the mind.

Well, we have a couple of choices, the plate is shrinking or
the bridges are crawling closer to the tuning pins but only
in the treble.  Maybe the soundboard is rising but only in
the treble end.  Maybe the bridge pins are playing jokes on
us.  Ok, ok, I know, the strings are chilling out!

Isn't this a wonderful business?  Just when we begin to
understand something someone moves the details around.

I'm loosing my hair for scratching at it.

		Newton

Fred Sturm wrote:
> 
> List,
>         A couple days ago, a tuning I did helped confirm some of my thoughts
> about unisons going out of tune in response to humidity change. The
> piano was a Wurlitzer grand out of the 50's (the time when Wurlitzer was
> a hotbed of experimentation), and has tuning pins "wedged" to the plate.
> (No pinblock. Web is extra thick, and drilled close to tuning pin
> diameter. Tuning pins are slit up from the bottom, and wedges driven in
> the slit to create a friction fit between pin and plate).
>         Obviously there could be no affect from expansion/contraction of
> pinblock, since there isn't any pinblock. Yet from C4 to C8 (I didn't
> start noticing until I got to C4) the right (treble side) strings were
> consistently 1 to 10 cents sharp of the left side strings, with middle
> strings in between. Very consistently - in excess of 90% of unisons were
> this way, mostly around the 5 cent range. I had previously tuned the
> piano in February, and had measured 30% humidity. This time (July) it
> was 60% humidity.
>         Just one more piece of evidence to confuse and confound the mind.
> 
> Regards,
> Fred S. Sturm
> University of New Mexico
> 
> "A mind is not a vessel to be filled, but a fire to be kindled."