QWhat makes cabinet doors tick? We have several theo- ries thrown around in meet-
ings, but we want the truth.
AThe key to answering this question is, “Wood in use does not shrink or swell unless its moisture content changes.” When the moisture
increases, wood swells and when the
moisture decreases, the wood shrinks.
So, a sticky door is one that has swollen
-- swollen since the cabinet was made.
To assist in your analysis, solid wood
only shrinks or swells in width and
thickness; lengthwise movement is rare,
very rare. Composite wood products,
like MDF, plywood, particleboard,
etc., move in all directions. In fact, if
many of these products are wetted with
liquid water, they tend to swell in thickness quite a bit, as the water is relieving
some of the stress when the product
was compressed when it was made.
So, you now have enough informa-
tion to analyze your particular situation.
You need to answer the question “With a
cabinet door that is rubbing or sticking,
is it the door that’s gained moisture and
swollen, or is it the frame or other wood
components holding the door that are
shrinking and pulling the door closer to
an adjacent door of component?”
For example, if MDF is used for the
main components of a cabinet, and
this MDF has been stored in a humid
location (which is not suggested)
before manufacturing the cabinet, the
MDF can swell a bit before use and
then when put into use, it will shrink
to the low moisture condition that is
typical of a house or office. With this
shrinkage, the door opening becomes
smaller. So the cause of rubbing is dry-
ing of the cabinet itself, not the door.
On the other hand, with solid wood,
the entire door frame is made with pieces
that run lengthwise, a direction in which
solid wood is stable, so the door opening is essentially fixed in size. Rubbing is
therefore because the door has swollen.
QWhy does our eastern 8/4 white pine lumber bow, both pieces, when we resaw it
into 4/4? The bow is so the
middle touches, but the ends do not.
AIt bows like this because it has lengthwise stress. This tress is caused by length- wise shrinkage in the wood;
such shrinkage and stress is not common in EWP, except in wood very close
to the center of the log -- probably the
first 10 years of growth. (In hardwoods
especially, such stress can arise due to
juvenile wood in the tree or growth
stresses in tree.) I suspect that you likely
have a moisture gradient, shell to core,
with the shell being somewhat drier.
Drier means the shell will be trying to
shrink a little more than the core, which
is wetter. In the 8/4 piece this shrinkage difference and the resulting stress
is balanced on both faces, so the piece
stays flat. But when you open the piece
by resawing, the new lumber pieces have
unbalanced stresses, face to face.
What makes cabinet doors stick?
What is brown maple?
by Gene Wengert
email@example.com WOOD DOCTOR’S Rx
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Wood Doctor’s Rx question and answers, go to
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.
Solid wood only shrinks or swells in width and
thickness; lengthwise movement is rare.