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physical properties of a wood species are those that affect its
appearance, weight, feel, and smell. Most craftsmen aren’t especially
concerned about feel and smell, since these change considerably when you
apply a finish. But appearance is paramount. Weight can also be
important if the project is meant to be moved or carried. The chart of
“Physical Properties of Wood” describes the appearance
and weight of common species. |
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WOOD COLOR
The unique color of a wood
species is determined by the
chemical extractives
embedded in the cell
walls. But the initial color of the raw, freshly cut wood doesn’t remain
unchanged. This color darkens somewhat when you apply a finish, even if
that finish appears clear and colorless. Most finishes also change the
hue, making it more amber. Craftsmen describe this as “warming up” the
wood color. In the chart of “Physical Properties of Wood,” you can see
how common finishes affect color.
Unfortunately, what you
can’t see is that the wood also changes color with age. As the surface
of the wood is exposed to air, it slowly oxidizes. Some woods are
photosensitive — exposure to ultraviolet light alters the extractives.
Both reactions change the wood color at the surface. This thin layer of
color-changed wood, sometimes only a few thousandths of an inch thick,
is the patina. |
Cherry is a photosensitive wood. The escutcheon
that once adorned this cherry drawer front blocked the light.
Consequently, the patina where the escutcheon once was is much lighter
than the surrounding wood. The patina of most woods grows darker with
age. However, in two species — walnut and mahogany — it grows lighter.
As they age, their patina becomes a soft gray color.*
Red
oak (top) has extremely large vessel elements which form visible pores
when sliced open. The long grain surfaces are said to have
open grain.
The vessel elements of Cherry (middle) are much smaller, they do not
form visible pores, and the surfaces have
closed grain.
Southern Yellow Pine (bottom) has no vessel elements, just an occasional
resin canal. The grain is neither open or closed.*
The
long grain surfaces of sawn lumber may display four types of grain
patterns.*
More
Tree Trivia:
The
fattest tree
in the world is the "Great Banyan" in the India Botanical Gardens near
Kolkata. The circumference of the main trunk is 52 feet and the crown
shades 4 acres. To experience what it's like to be under a Banyan tree
looking out, click
HERE. Unbelievably cool!
You
can tap birch trees for their sap and make syrup much the same as maple
trees. Birch syrup is easier to digest, has a lower glycemic index, and
is higher in nutrients than maple syrup.
The
average 2000-square-foot house requires 16,000 board feet of lumber and
11,000 square feet of sheet materials. |
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When restoring or refinishing
antiques, be careful not to sand through the patina. If you do, the wood
may appear blotchy – darker in some areas than in others. |
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WOOD TEXTURE
Texture depends on the size of the longitudinal cells. In hardwoods,
this refers to the size of the
fibers and the
vessel elements; in
softwoods, it’s the
tracheids. Fine-textured woods have small cells,
while coarse woods have larger ones.
WOOD GRAIN
When the
vessel elements
in hardwoods are sliced open, they create depressions called
pores.
Woods with large pores that are easily visible to the naked eye are said
to have an
open grain. Those with
smaller pores, to small to see clearly, have a
closed grain.
Note: Because softwoods do not have vessel elements, these terms
don't apply. For practical purposes – such as preparing and finishing
the surface – softwood grain is closed.
GRAIN PATTERN
The normal orientation of the longitudinal cells determines a species’
characteristic grain pattern. There are four categories.
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In straight grain, the longitudinal cells grow fairly straight and
parallel to the axis of the trunk. |
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In wavy grain, the cells undulate in short, even waves. This
sometimes produces curly figure. |
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In irregular grain, the cells undulate around knots
or in no discernible pattern.
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In interlocked grain, the cells spiral around the trunk, reversing
direction every few growth rings. This produces ribbon figure.
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WOOD WEIGHT
The weight of a species can be gauged from its
specific gravity.
The higher the specific gravity, the heavier the wood. To figure the
precise weight of a board foot (1
✕
12 ✕
12 inches) of a wood, multiply its specific gravity by the weight of a
cubic foot of water, 62.5 pounds, then divide by 12. The weight of
cherry, for example, is 2.6 pounds per board foot:
0.50
✕
62.5 ÷ 12 = 2.6
Outside of North America,
wood is sold by the cubic meter and weight is calculated in kilograms.
To figure the weight of a species, simply multiply the specific gravity
by 1000. Cherry weighs 500 kilograms per cubic meter.
0.50 X 1000 = 500
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USING THE CHART
The chart of “Physical Properties of Wood” is divided into three parts
-- North American Hardwoods, North American Softwoods, and
World Woods, or woods from other places than North America. To
access any part, click on the title below. To see the properties for any
wood species, click on its name. |
North
American Hardwoods
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Alder, Red |
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Ash |
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Aspen |
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Basswood |
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Beech |
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Birch, Yellow |
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Butternut |
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Cherry |
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Chestnut, Wormy |
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Elm, Red |
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Gum, Red |
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Hickory |
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Holly |
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Maple, Hard |
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Maple, Soft |
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Oak, Red |
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Oak, White |
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Osage Orange |
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Poplar, Yellow |
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Sassafras |
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Sycamore |
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Walnut |
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Willow |
North
American Softwoods
World
Woods (Other Than North America)
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Back to the top *Indicates that you
can enlarge a photo by clicking on it. To reveal the information in a "Superphoto,"
first enlarge it and then move the cursor over it. |
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