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Natural Characteristics Part 1 |
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Effects of Growth
Rings
The amount of annual growth influences the "look"
of sawn lumber. Growth rings of a tree are distinctive
because of the light and dark colors. The lighter portion
is usually grown in the spring and is called "summerwood."
The size of the growth rings varies from species to species
and even tree to tree depending on many factors including
genetics and growing conditions. These two examples have
approximately the same growth ring orientation yet look
very different. |
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| Wide Growth Ring |
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| Narrow Growth Ring |
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Burl
Grain
Burl grain is common in most species and is also
known as curly grain, burly grain, fiddleback or
figure wood. Various causes of burl grain include
knot location, damage to the bark cambium layer,
and tree genetics. Burl grain is often a desired
characteristic for specialty products, but can be
difficult to machine. |
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| Hard Maple |
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| Red Oak |
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Soft Maple |
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Tiger Stripe / Cross
Fire
This unique grain pattern (also called zebrawood) is common
in red and white oak and both hard and soft maple, as
well as other species. Tiger stripe is most often found
along with burl grain, which can be difficult to machine
or sand. Wood with this grain characteristic is often
quite dense compared to the average density of the species.
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| Hard Maple |
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| Soft Maple |
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Bird's Eye
Bird's-Eye, as seen in this hard maple example, is a small
area in the wood where fibers are contorted to form circular
figures that resemble birds' eyes on the surface of the
board. It is common in hard maple and rare in other species.
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| Bird's Eye |
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Knots
Knots vary in size, shape, structure, and color. Because of
this, it may be the most difficult characteristic of wood to
classify. Knots also account for large yield losses in our industry
and cause us to buy Select and Better grades of lumber, as opposed
to #2 Common grade, at a significant cost increase. Because
of these factors, it is important to understand (as best we
can) the knot variations.
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Closed
Knot
A closed knot has a flat face with no openings in the
lumber surface. |
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Open Knot
An open knot may occur in the form of a very small pin-sized
hole to a large gaping hole in the lumber surface. |
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Unsound
Knot
An unsound knot, also known as a loose knot, has a portion
that will move readily. |
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Pin Knot
A pin knot is a small, sound, and tight knot. |
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Sound Knot
A sound knot, also known as a tight knot, is completely
solid with no portion of the knot moveable. It is as hard
as the surrounding wood and shows no sign of decay. |
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Knot Cluster
A knot cluster is a grouping of usually small knots. |
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