[pianotech] pitch and temperature

[Ron Nossaman]

On 1/10/2011 11:10 AM, Gene Nelson wrote:
> 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

The rate of moisture transfer in the wood is related to the difference 
in MC, and/or RH%. EMC of the panel in 60°F at 65%RH would be a bit over 
12%. To get the panel to 6%MC took soaking it in a 30%RH or less at over 
70°F for considerable time. The closer to EMC the wood is to the 
environment, the slower the moisture transfer. The farther from EMC the 
wood is to the environment, the faster the moisture transfer. If your 
garage had been at 30%RH, whatever the temperature, you would have had 
all day.

Even so, in a strung instrument, that couple of hours before the wood 
reacted to a 35%RH increase would mean the strings had already reacted 
to any temperature change, and the plate was probably still catching up.

Ron N