Formula for rate of change of EMC?

[Farrell]

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Word document with formula etc. is attached. I think the formula can be =
useful for getting some kind on an initial guesstimate of how long to =
expect a piece of wood to dry. I don't think it will be very useful for =
predicting how fast a soundboard panel will go from 9% MC to 6% MC.

I have found the best way to closely monitor wood MC is by weighing =
smaller pieces and/or measuring across grain of a panel. I have two =
panels in my hot box right now. They've been in there for six days at =
about 92 degrees F and 27% RH. They have shrunk 3.5 and 5 mm as of today =
and they are still shrinking. What I do is take them down a tiny bit =
drier than I want them (if target is 6% MC, I'll go to 5.5% or anything =
a little lower than 6%) and then let the RH rise just a tad and make =
sure they grow a tiny tad - that way I know for sure the panel had =
equilibrated at the lower RH - if it still seems to shrink, go tune =
pianos for a week and then go back and check the hot box. Weighing =
samples works quite well also - although you always will wonder if the =
sample is drying a litte faster because of its increased surface =
area/volume ratio, and its increased percentage of end grain.

I also found a reference to the two soundboard CLAMP articles:

David Hughes soundboard press in PTGJ is August 1993

Clair Davies soundboard press - August, September, October 1997.

Terry Farrell

 =20
----- Original Message -----=20
From: <BobDavis88@aol.com>
To: <pianotech@ptg.org>
Sent: Saturday, August 09, 2003 11:24 AM
Subject: Formula for rate of change of EMC?


> I know a while back someone posted the formula for rate of change of =
EMC over=20
> time. It was based on the ambient humidity and the thickness of the =
wood.=20
> I've been looking through the archives and through the Wood Handbook, =
and I can't=20
> find it. Probably staring right at it. Anyway, will whoever?
>=20
> Thanks
> Bob D
> 
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