[pianotech] pitch and temperature

[Gene Nelson]

When I put a new board in my Knabe I did it in my unheated/unairconditioned 
uninsulated garage.
Dried the blank under blankets over a heater to  6%mc. Measured across the 
grain and made marks. When removed from covers and heat the garage was about 
60F and 65%rh. As I recall I had about two hours working time before the 
unfinished blank started to grow.
Gene
----- Original Message ----- 
From: "Tony Caught" <acaught at internode.on.net>
To: <pianotech at ptg.org>
Sent: Monday, January 10, 2011 1:14 AM
Subject: Re: [pianotech] pitch and temperature


> 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
>