the less successful drying will be in
controlling the stain. In other words,
the only effective control today for
brown stain is to avoid slow drying by
avoiding long log storage (especially
on valuable logs), use low RHs in the
kiln or in air drying, and using brisk
Symptom. Wet pockets are small zones,
perhaps several inches along the grain
and several inches wide in the interior
of lumber, that have an extraordinary
high moisture, compared to the adjacent moisture within the same piece of
lumber. They are rare in 4/4 lumber,
but a somewhat common in 8/4. They
are more common in wide lumber
pieces. Wet pockets seem common in
cottonwood, aspen, elm, white pine,
redwood and hemlock.
Cause. The cause of such pockets is
likely related to a bacterial infection
in the living tree, and they cannot be
identified when the wood is green. In
my experience, wet pockets are more
common when drying is accelerated.
The problem with a wet pocket is
that eventually the water will leave this
wet pocket and, when the water leaves,
the pocket can shrink and then can
develop collapse or checking.
Cure. The only reliable cure for wet
pockets is patience in drying. But, long
drying times are expensive and may
encourage other defects to develop.
Therefore, some wet pockets can be
expected even when drying is properly
Technology now exists to use an
in-line moisture meter to find wet
pockets in dry lumber. Such wet pocket
lumber pieces can be withdrawn from
dry lumber production and allowed to
remain in storage for 4 weeks (give or
take), thereby allowing the wet pocket
to dissipate. ;
Part II of Rx for better drying
will appear in the December
issue of FDMC.
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