Hygrometer

[Farrell]

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And hence my question from yesterday or whenever: ".....is +3% of target =
mc good enough when drying a board down to produce "consistent" =
results"?  I just don't know how much leeway we commonly have to produce =
consistent results. When I do something for the first time, I tend to =
error toward the overkill end of the spectrum, hence my persistent =
questioning. Thanks for your post, I think I have the info I need now.=20

Terry Farrell

Below is my post from the other day:

The little cheapies seem to run in the +5% RH accuracy range. That is =
too inaccurate for drying a board (I think!). With that inaccuracy, if =
one were shooting for a moisture content of 6.5%, the best you could do =
is to get it somewhere between 5.8% and 7.2% moisture content. I would =
like to get it closer to target than that. SNIP  One with RH reading =
accurate to within +2% will get me to within a mc of 6.2% to 6.8% if my =
target is 6.5%.
=20
Hey Del or Ron, is +3% of target mc good enough when drying a board down =
to produce "consistent" results?

----- Original Message -----=20
From: "Ron Nossaman" <RNossaman@cox.net>
To: <pianotech@ptg.org>
Sent: Friday, August 30, 2002 9:48 AM
Subject: Re: Hygrometer


> How "good" is "good", and how critical is absolute accuracy to your =
purpose=20
> and process? No two pieces of wood are going to react quite the same =
to=20
> humidity changes, so your chosen material is every bit as much a =
detriment=20
> to "accuracy" as a cheap hygrometer. You can buy a decent sling=20
> psychrometer for something in the $80-$100 range and use it as a cross =

> check and calibration device for your cheapie, for your own =
information and=20
> peace of mind. You can also use various saturated salts to calibrate. =
Try=20
> http://www.natmus.dk/cons/tp/satslt/satsalt.htm .
>=20
> As I said, the most effective way around the need for absolute =
accuracy is=20
> to build soundboard assemblies that are more tolerant of minor=20
> irregularities. I dry panels down with a little space heater using the =

> piano as my hot box. The panel lays on top of the rim, the heater goes =

> underneath, and moving pads go over the top. My little +-2% hygrometer =
sits=20
> on top of the panel, under the pads. A couple of days later (depending =
on=20
> the season), when it's showing 30%RH, the panel's ready to work. The=20
> piano's probably a little smaller too, but that doesn't seem to be a=20
> problem. If I was running a high volume operation, I'd have more floor =

> space and build a dedicated box, but I don't expect the basic system =
would=20
> be much more sophisticated than what I'm using now except for =
controlling=20
> the heat source with a humidistat - and not shrinking the piano too, =
of=20
> course. I'd prefer this, since the panel could "soak" a while longer =
than a=20
> couple of days and more nearly stabilize, but I haven't noted any =
problems=20
> from the rather crude and inelegant way I do it now.
>=20
> Ron N
>=20
>=20

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