Results are In! Re: moisture in wool or wood.

[Farrell]

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I have no doubt my little experiment is imperfect. I'll have to think on =
some of the comments I have read and see where, if anywhere, to go with =
this. And please, if only I could be as eloquent as Howard Rosen's =
recent posts (he could criticize me and I would thank him profusely with =
heartfelt  tears in my eyes!), I'm not trying to be argumentative in any =
of this, but rather just trying to understand.

"You need to remember my previous post, where I mentioned that there is =
some surface fiber swelling.  You should also remember my suggestions =
for testing - drilling the hole with the wood sitting in the shop at 50% =
RH isn't a good way to measure the change."

The reason I drilled at 50% RH was to reasonably simulate a real flange. =
Presumably, a flange made in the factory is not drilled at any extreme =
of RH.

"If carried out properly with a larger change in humidity, the drill rod =
will become very tight in the center pin holes when the wood is dry.  =
Your test did not change the moisture content in the wood enough for =
such a small piece of wood to change shape, but it was evidently enough =
for a slight change in the surface fibers. As I originally suggested, =
you need to drill the hole when the wood is at one extreme or another, =
then test the fit when the wood has reached the opposite extreme."

Here again, I can only suggest that we are trying to look at how a real =
flange would react under real conditions (or nearly so). So, if surface =
fibers swell with X amount of moisture content increase and make the =
center pin tighter, would this not mean that the hole gets smaller with =
increasing RH/moisture content? BUT, I would also say that even going to =
EXTREMES should produce a consistent effect, so your point is well =
taken. Hmmmmmmm. Some pondering is needed here.

"By the way, a closed container with water inside does not necessarily =
reach 100% humidity in the air, as you suggested.   That would depend on =
the temperature. Try it with a humidity gauge in there.  I suspect that =
the relative humidity went from your measured ~50% point when you =
drilled the hole, up to maybe 75% in the closed container."

Oops. I see I am as guilty as you in intermixing use of "humidity" and =
"relative humidity". I believe, however, it is clear that we are both =
talking about RH. You indicate your suspicion that "the relative =
humidity went from your measured ~50% point when you drilled the hole, =
up to maybe 75% in the closed container". I did place a hygrometer in =
there and it does go up to 100% RH. That's basic chemistry. The water =
coming out of solution (evaporating) will reach equilibrium with water =
vapor in the surrounding air, thus the air will hold as much water vapor =
as it can at equilibrium, which is the definition of 100% RH.

"With such a small cross section of wood, the amount dimensional change =
is not enough with such a small change in moisture content."

Again, popular belief is that changes in humidity in real piano =
environments can cause real action centers to get tight and/or loose. So =
I want to see what happens under something close to realistic =
conditions. An argument could be made that 100% RH is not realistic. =
True (although I'm sure there are some out there who would argue), but =
RHs up in the 90%+ range are not unheard of, so I think 100% represents =
a realistic extreme.

"I have done the exact same test you did with very definitive results.  =
Try again, but start with the wood either dry or wet - not in the =
middle.  Bake a few flanges in the oven at 250 degrees for and hour, =
then drill the holes right away when you take them out.  Check the fit =
after drilling, then check them the next day after the flanges reside in =
your wet chamber for a while."

I'm concerned with the validity of introducing such an extreme of =
temperature. Clearly, 250 degrees is way out of range of anything =
normal. How does such an extreme temperature affect the wood? The temp. =
alone could have an effect of shrinking or expanding wood fibers/cells. =
Most things expand with increasing temperature (i.e., metal). Perhaps =
your flange hole was drilled when cells in that area were at an expanded =
state (temperature perhaps having more an effect than the obvious low =
moisture content) because of the excessively high temperature, and then =
when cooled, they shrank, causing the flange hole to be larger. Maybe??? =
Unless we have some kind of definitive knowledge of extreme temp. effect =
on wood, I should think such an extreme would invalidate any experiment =
of the type we are looking at.

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com
  ----- Original Message -----=20
  From: Donald Mannino=20
  To: pianotech@ptg.org=20
  Sent: Sunday, January 14, 2001 12:18 AM
  Subject: Re: Results are In! Re: moisture in wool or wood.


  At 11:07 AM 1/13/01 -0500, you wrote:

    Good idea Richard. I think I will try that. I have lots of old =
flanges
    laying around. My first trial there was to simply see whether a =
flange hole
    got bigger or smaller with increased humidity/moisture content. It =
is clear
    to me, contrary to apparent popular belief, that a hole in a flange
    decreases in diameter with increased humidity/moisture content.

  Terry,

  You need to remember my previous post, where I mentioned that there is =
some surface fiber swelling.  You should also remember my suggestions =
for testing - drilling the hole with the wood sitting in the shop at 50% =
RH isn't a good way to measure the change.

  If carried out properly with a larger change in humidity, the drill =
rod will become very tight in the center pin holes when the wood is dry. =
 Your test did not change the moisture content in the wood enough for =
such a small piece of wood to change shape, but it was evidently enough =
for a slight change in the surface fibers.

  As I originally suggested, you need to drill the hole when the wood is =
at one extreme or another, then test the fit when the wood has reached =
the opposite extreme.

  By the way, a closed container with water inside does not necessarily =
reach 100% humidity in the air, as you suggested.   That would depend on =
the temperature. Try it with a humidity gauge in there.  I suspect that =
the relative humidity went from your measured ~50% point when you =
drilled the hole, up to maybe 75% in the closed container.  With such a =
small cross section of wood, the amount dimensional change is not enough =
with such a small change in moisture content.

  I have done the exact same test you did with very definitive results.  =
Try again, but start with the wood either dry or wet - not in the =
middle.  Bake a few flanges in the oven at 250 degrees for and hour, =
then drill the holes right away when you take them out.  Check the fit =
after drilling, then check them the next day after the flanges reside in =
your wet chamber for a while.

  Don Mannino RPT



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