[pianotech] pitch and temperature

[J Patrick Draine]

The change in the soundboard etc.'s moisture content is much, much slower
than the affect of temperature changes on the strings (and, the plate more
slowly than the strings).
I suggest you read Ron N's post again.

Keep dry (cousins are sandbagging in Gympie; it's just cold here in
Massachusetts),
Patrick Draine


On Mon, Jan 10, 2011 at 4:14 AM, Tony Caught <acaught at internode.on.net>wrote:

> Hi Ron,
>
> The land I take it is in the middle of the swamp with a few gators for
> company.
>
> My Take.
> "a loaner sat on the moving van in freezing weather overnight"
> Drives the moisture out of the soundboard.
>
> "brought on stage indoors in a warm theatre"
> Soon as the piano hits the air it starts to absorb moisture at a
> (scientific
> word) fantastic rate.
> Soon as you open the piano to tune it the moisture absorbsion rate
> increases.
>
> I found out a long time ago that removing a piano from indoors at 21
> degrees
> C and 40%RH to outdoors at 32 degrees C and 80% HR and then tuning it to be
> to say the least, challenging. The temp does not change that much but the
> piano keeps changing whilst you are tuning.
>
> Now you say that the strings change 1/2 way through the tuning. The
> question
> is is this caused by the soundboard expanding or shrinking or the strings
> expanding or shrinking.
>
> Or, my head just shrinking so the sound is expanding.
>
> Tony
>
>
>
> Tony Caught
> acaught at internode.on.net
>
> -----Original Message-----
> From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On
> Behalf
> Of Ron Nossaman
> Sent: Monday, 10 January 2011 3:33 PM
> To: pianotech at ptg.org
> Subject: Re: [pianotech] pitch and temperature
>
> On 1/9/2011 8:57 PM, Gene Nelson wrote:
> > Thanks everyone,
> > I was trying to come up with a chapter technical on the subject.
> > Possibly an approach from co-efficient of expansion for steel piano
> > wire, isolating for the one thing that moves the fastest and possibly
> > the most? The math is beyond me.
>
> The math is pretty simple, and I'm math deaf. The expansion coefficient
> of music wire and gray iron are pretty close. The difference is in the
> cross section of the parts. It takes little time for a temperature
> change to migrate through 0.040" diameter wire compared to 0.5" iron.
> That's it.
>
>
> > My challenge was a couple years ago in the winter, a loaner sat on the
> > moving van in freezing weather overnight, brought on stage indoors in a
> > warm theater and I had about an hour to work with it.
> > Gene
>
> There's the problem. The strings changed fairly quickly, maybe up to
> half way through the tuning, where the plate caught up about four hours
> later. This is an impossible situation, and any tech who hopes to
> anticipate the changes and accommodate them to all come together in a
> good tuning at a specific time is eligible for a really good land deal I
> have available in Florida.
> Ron N
>
>
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