by Gene Wengert
email@example.com WOOD DOCTOR’S Rx
QWe are seeing some end checking, and rarely some face checking, in the solid
oak panels that we manu-
facture. The checking is right after
finishing. We are thinking that our
ovens might be too hot, or maybe the
residence time is too long. Any guid-
ance before we start changing things?
AI suppose that it is indeed possible that the oven is too hot or the residence is too long, but I do believe that
this is a very rare reason that we see
end and face checking. Here is why:
The tension strength of dry wood is
around 10,000 pounds per square inch.
So, somehow, we are going to have to
develop a huge amount of tension force
within the wood while it is in the oven.
We do know that an oven is typi-
cally about 1 percent relative humidity,
So, the checks you are seeing are be-
cause a) either the wood is weaker than
normal or (b) if the end checks are at
the glue joint, the glue joint is weaker
If the wood is weaker than normal,
we would also see that the weight of
the wood is much lighter, maybe 50
percent lighter, than normal. This is
indeed a rare event, but it is worth
checking on. When you get a failure,
check the weight.
The wood can also be weaker than
normal due to a bacterial infection
in the tree that destroyed some of the
strength. In this case, we almost always
notice a foul odor and checks (some-
times called shake) that run parallel to
the growth rings rather than across the
rings. Again, this is not common.
So, here is your answer: The most
common reason for weak wood is that
there is a preexisting check, oftentimes
an end check from drying that was not
totally eliminated during the cutting
of the blanks. The very end of an end
check (looking at the end of the lumber) is oftentimes easy to see in rough
lumber, especially on a dry day (On a
humid day they may swell closed and
become temporary invisible.), but the
lengthwise extent of the end check is
often hard to see precisely, especially
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Gene Wengert, “The Wood Doctor,” has been training
people in efficient use of wood for 35 years. He is
extension specialist emeritus at the University of Wisconsin-Madison.
The checks you are seeing are because the wood
is weaker than normal or the glue joint is weaker