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Re: Hello - boards - moisture



>1. Moisture in the boards: how do you bookbinders know
>when your cover boards are completely dry? I feel them
>and if they feel cool to the touch I presume there is
>some moisture left. And of course if they start
>bending the minute they come out from under the
>pressing boards! But is there a better way to tell?

Other than checking if the board feels cool I have no further suggestions,
but I do have an idea for reducing the drying time for such assemblies.
Normally, boards are clamped between essentially waterproof surfaces, and
the only
way for them to dry is by the moisture migrating to the edges and
evaporating.

If you were to place corrugated cardboard above and below the davey board
(and between the glued pairs, if several are clamped), and blow air through
the ends of the cardboard, drying should proceed much faster and more
evenly.

Some notes:
Make sure there is cardboard between every glued-up set, so that all dry
evenly. If you
have cardboard on just one side of a set, it will probably come out of the
clamp with
a permanent curve to it.

The acidity that might exist in the cardboard should not be a concern, since
the
moisture is migrating from the board to the cardboard, and not the other way
around.

The crush strength of the cardboard limits the amount of clamping pressure
you can
apply, so you might want to clamp just the board under heavy pressure for a
while
to produce good contact between the glued surfaces, then open the clamp,
insert the
cardboard, and apply lighter pressure.

You can, in theory, check the drying progress by comparing the temperatures
of the
air entering and leaving the cardboard. If there's still moisture
evaporating, the
exiting air will be cooler. I say "in theory" because the temperature drop
may be
too small to measure even though the boards are not dry enough yet.

This technique is often used by hand papermakers to dry their paper. We use
it ourselves
for this purpose (although we haven't tried it for gluing up binder boards).
Triple-corrugated cardboard (about 3/4" thick) is available from several
papermaking
suppliers, including ourselves. The main problem is that shipping it is a
pain! (but
then, the same applies to binder board!)

I just hope I am not suggesting something that is already common practice!

-Kevin Martin
 the Papertrail

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