we see the biggest problem in the summer. The reaction begins the moment
a tree is cut down. Therefore, in summer we need to move very quickly from
woods to sawmill to kiln.
The best color is obtained if we go
directly into the kiln and if we use a
fairly large depression or low humidity
initially. That is, fast drying.
Check page 75 in Drying Hardwood
Lumber for the “white” hickory kiln
schedule. Air flow must be brisk.
The initial conditions in the first 24
hours are critical. Remember that it is
not what you set but the actual conditions that matter.
QWe get our lumber at 6 to 8 percent MC. We check its moisture to confirm. So,
should we set the plant at
7.0 percent EMC (halfway between),
or should we set the plant a little
drier, like 6. 8 percent EMC because
we want to discourage any drying at
ABecause a little drying shrinkage is more serious than a little moisture gain, the general recommendation is that the plant should be a little
bit drier than the mid-point value. So,
6. 8 percent EMC (about 35 percent
RH) is better.
A technical note I have discussed
before: When wood that has been
drying is subjected to moisture regain,
there is a lag of perhaps 3/4 percent
MC before any swelling begins.
So, it is safe to be a little drier to
avoid shrinkage because the exposure
to higher humidities will have this
Because humidities in air drying
can be too high sometimes, encouraging the reaction, air drying color is
not as good as immediate, proper kiln
Note that these comments apply
to beech, maple, ash and other white
wood species. ✚
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