<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; =
charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1106" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY>
<DIV>Well, that is more-or-less what I did Del. My aim was to calibrate =
a
panel-type MC gauge, so RH and MC stability were my aims, not =
necessarily
measuring rate of change. But I do have some data that might shed some =
light on
this subject.</DIV>
<DIV> </DIV>
<DIV>I took 2 to 6 blocks of wood (approx. 8 mm x 100 mm x 100 =
mm - my
0.01 scale only goes up to 100 grams, so I needed to stay with block of =
less
than that - they were all between 50 and 95 grams) - mostly spruce, but =
some
mahogany and hard maple (all pretty much reacted the same except the =
maple was
slower to change MC overall). I placed blocks in my hot box and varied =
RH and
left it at different levels for several days to be sure wood MC had =
stabilized.
I would weigh blocks every day. Experiments ran (I actually did several) =
up to
34 days. If anyone wants the raw data, I can send it to you. Some =
approximations
follow (I looked for a near-equilibrium conditions, a rise or fall of =
RH, and
then near-equilibrium conditions again):</DIV>
<DIV> </DIV>
<DIV><U>RH &nb=
sp;
DAYS =
MC =
</U></DIV>
<DIV>20% drop 2.5
2.7% drop</DIV>
<DIV>14% rise
5.0 =
1.3%
rise</DIV>
<DIV>12% drop
5.0 =
1.3%
drop</DIV>
<DIV> 9% rise =
4.0 =
1.0%
rise</DIV>
<DIV> </DIV>
<DIV>These data represent fairly stable endpoint conditions (both hot =
box RH and
MC, except for the 20% drop, the wood had not stabilized before the hot =
box RH
went back up a bit, but MC did in fact drop 2.7% in 2.5 days, it =
had simply
not yet reached equilibrium).</DIV>
<DIV> </DIV>
<DIV>From these data, it looks to me like wood looses moisture as easily =
as it
gains it.</DIV>
<DIV> </DIV>
<DIV>Terry Farrell <SPAN =
id=__#Ath#SignaturePos__></SPAN> </DIV>
<DIV>
<DIV> </DIV></DIV>
<DIV>----- Original Message -----<BR>From: "Don" <<A
href="mailto:pianotuna@accesscomm.ca">pianotuna@accesscomm.ca</A>><B=
R></DIV>
<DIV>> Can someone suggest a better protocol for such an =
experiment?</DIV>
<DIV> </DIV>
<DIV>----- Original Message ----- <BR>From: "Delwin D Fandrich" <<A
href="mailto:pianobuilders@olynet.com">pianobuilders@olynet.com</A>>=
<BR><BR>Yes.<BR><BR>Put
a piece of wood--since we're interested in piano tuning stability, =
let's<BR>make
it a Sitka spruce panel about 8 mm thick by, say 250 x 250 mm--in
a<BR>hermetically sealed environment stabilized at 70º F (or 90º F, =
or
whatever,<BR>just so the temperature remains stable throughout the =
experiment)
and 50%<BR>RH. With the wood sample placed on a very precise and =
accurate
scale,<BR>monitor its weight until it has stabilized. Rapidly raise the =
RH to
70% and<BR>periodically monitor and record the weight change over time =
until the
weight<BR>of the sample has again stabilized. Rapidly take the RH back =
down to
50%,<BR>again monitoring the weight change at the same time intervals. =
Following
the<BR>same procedure take the RH further down to 30% and then back up =
to
50%.<BR><BR>If you take weight readings frequently enough this should =
give you a
pretty<BR>good idea of the rate at which the sample absorbs and desorbs
moisture. In<BR>the end I expect you'll find it's about the same both
ways.<BR><BR>Del<BR><BR>_______________________________________________<B=
R>pianotech
list info: <A
href="https://www.moypiano.com/resources/#archives">http://www.ptg.org=
/mailman/listinfo/pianotech</A><BR></DIV></BODY></HTML>