QWhat makes a 2 x 2 inch square (about 24 inches long) that initially has the
sides at perfect 90 degrees
so it has a square profile become
slightly diamond shaped with the
sides no longer at 90 degrees to each
AThis diamond shape occurs for two reasons: 1) Because the moisture content is changing and 2) because
the annual growth rings, as seen from
the end of the piece, are not running
parallel to two faces (and perpendicular to the other two faces), but are running at an angle to the faces.
The worst case is when the growth
rings run from one corner to the opposite corner. The reason that the ring
orientation on the end grain is important is that wood shrinks, when there
is a moisture loss, twice as much along
or parallel to the rings than across the
rings. This difference in shrinkage
results in a square becoming diamond
shaped. This “un-squareness” is easy to
detect in many wood products, especially in a butcher block top made with
end grain pieces.
This same shrinkage difference
effect is why a perfectly round piece becomes oval shaped when it dries. There
is considerably more shrinkage along
the rings than across the rings when
looking at the end grain. However, a
slight oval shape is hard to detect visually in most wood products.
Note: A gain in moisture causes the
same distortion, but in the opposite or
reverse direction; there is more swelling parallel to the rings than across. ;
704.799.0100 • www.weinigusa.com
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“A gain in moisture causes the same overall distortion,
but in the opposite or reverse direction; there is more
swelling parallel to the rings than across.”
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