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Wood
WOOD is "the hard fibrous substance
beneath the bark in the stems and branches of trees and shrubs."
It is a strong organic material
that is easily worked.
There are many
species, each with its own characteristics.
CHARACTERISTICS OF WOOD
The characteristics include color,
grain, hardness, and strength.
COLOR is the shade of the "raw"
wood before it has been treated with any finishing agents.
GRAIN is the design in the wood
made by the layers of fibers and the size and arrangement of the pores. The
fibers are stacked in layers and interspersed with the pores.
The PORES are the openings through which fluids are absorbed or
discharged. They may be small and compactly
distributed, producing CLOSE-GRAIN wood, or they may be large and
widely-dispersed for OPEN-GRAIN wood.
The pattern of the fibers makes the
FIGURE of the grain. Different figures may be obtained by
Cutting the wood in different
directions;
Using deformed or abnormal areas
of a tree;
Exposing the rays, curly grain,
or ends of the wood as it is cut.
HARDNESS - the capacity of the wood
to resist abuse.
STRENGTH -
Ability to resist force and stress.
SPECIES
OF WOOD
There are many varieties of wood
available; however, only particular species are practical for
construction and the manufacture of furniture.
MAHOGANY
Used in both solid and veneer form.
Different varieties include:
African mahogany
West Indian mahogany
American mahogany
Takes stains well, and it is
usually finished with a light reddish-brown or brown stain that brings out the
figure
ROSEWOOD
An ornamental wood found
principally in Brazil.
The heartwood starts to decay
before the tree is mature. By the time the tree is felled the center is hollow
and the wood can only be cut in half-round flitches.
The wood color runs from red to
brown, and it is streaked with black lines of resin.
TEAK
White sapwood and golden yellow
heartwood in the young tree, but when the heartwood is seasoned, it changes to
a brown mottled with dark streaks.
A pleasant, aroma emanates from the
heartwood and it retains this fragrance for many years.
Teak timber is strong, of average
hardness, and of medium weight.
EBONY
Grows in India and Ceylon, has a
narrow trunk with black, charred-looking bark, white sapwood, and heartwood
with an intense black color.
Jamaican or American ebony is
produced from a tree or shrub which has a trunk that seldom grows more than
four inches in diameter. The heartwood has a rich dark brown color, great
weight, and exceptional hardness.
WALNUT
Widely used in solid and veneer
work.
American black walnut varies in
color from light, creamy sapwood to warm grays and light brown.
Its pores are irregular but large
in size and evenly distributed.
It has a wide range of figures
including burl, crotch, stump wood, plain stripe, and highly figured longwood.
OAK
Color spread from white to light
and reddish brown. Its pores are large in the spring wood and decrease
abruptly in summer wood.
It has an unusually large ray
extending from the center to the bark.
MAPLE
Cut from American or Canadian
forests of sugar, hard, or rock maple trees.
Light pink to reddish brown in
color. It has very small regular pores that require no filling and a hard
texture that makes it difficult to work.
RED GUM
Reddish brown heartwood and grayish
white sapwood.
Has very small pores and a smooth
surface, but the texture is very soft.
It does not hold up well under hard
use as it dents and warps easily..
ORIENTAL WOOD
A unique timber from Queensland,
Australia.
Brown with an overcast of salmon,
green, gray, and sometimes black bindings.
SATINWOOD
Comes from Ceylon, India, and the
West Indies.
It has a silk sheen and a golden
yellow color that mellows with age.
MYRTLE
BURLS
Cut from California and Oregon
trees in which the plain wood, stump wood, and burl figures have unusual
designs.
The pores are numerous and
regularly distributed; these finish as highlights that make the wood more
attractive.
CHERRY
wood
light to dark reddish brown in
color.
The pores are rather close; the
grain has a very slight figure; and the texture is medium hard..
SUGAR-KNOTTY PINE
Popular because of its knotty
appearance.
This wood has a very soft texture
and is generally made into veneer for hardcore plywood.
The wood is whitish or cream-.
PECAN
or HICKORY
a reddish brown color that is often
accented with dark streaks.
The grain has very little figure,
and the pores are small and require only slight filling.
Other
woods are:
Japanese and Korean ash;
American aspen and birch;
African avadire, bubinga, sapeli,
tigerwood, and zebrawood;
Philippine narra and paidao; and
primavera.
TYPES
OF WOOD MATERIALS
SOLID WOOD is cut entirely from a
single log. It is strong and durable; therefore, it is usually used to make
the structural parts of buildings.
It warps easily and has an expansion/contraction
problem. Also, Some species are in limited supply
and, as a consequence, are expensive.
TYPES
OF WOOD MATERIALS
VENEER is a thin sheet or layer of
fine or costly wood that is cut from a log or part of a log called a FLITCH
VENEERING is the technique of
gluing this sheet to a plain, stable ground wood.
The standard thickness for veneer
is one-twenty-eighth inch. Some may be as thick as one-sixteenth inch or as
thin as one-sixtieth inch.
Special
veneers
Cut from the unusual parts of the
tree.
BURL VENEERS
BUTT or STUMP VENEERS have a
wavy, rippled marking.
CROTCH VENEERS, taken from the
twisted fibers below the fork, have a swirl design.
Veneer
surfaces
SLIP MATCHED VENEERS are sheets
joined side-by-side to make it look as if the pattern is repeated.
BOOK MATCHED VENEERS have the
adjacent pieces of the flitch fastened side-by-side like the open pages of a
book.
DIAMOND MATCHED VENEERS use four
pieces cut diagonally from the same material and fitted together to form a
diamond.
REVERSE DIAMOND MATCHED VENEERS
also show a diamond, but they are fitted together exactly opposite to the
diamond matched.
CHECKERBOARD MATCHED VENEERS give
each piece a onequarter turn so that a checkerboard effect is produced.
FOUR-WAY CENTER AND BUTT MATCHED
VENEERS join four pieces side-to-side and end-to-end.
INLAY
Veneers cut into small pieces of
various shapes and sizes so that special designs and pictures can be created.
Inlay may be produced through several methods.
MARQUETRY
Each piece of the pattern is
cut individually and then the sections are glued onto a groundwork.
PARQUETRY
An inlay form characterized by
a repeated geometric design. It is built up of blocks or individual
elements which are assembled into patterns that move continuously and
consistently across the groundwork.
BANDING
A form of inlay in which strips
or strings are set in around the edges of a piece as ornamentation.
MOLDING
A strip of shaped or carved wood
that is both decorative and practical.
It may be attached to the exteriors
of doors and drawers and the edges of cabinetwork to give a finished
appearance to an item and to enrich its design.
PLYWOOD
A manufactured wood with three or
more plies or pieces glued together, one atop the other, to form a panel.
The grain of each ply is set at
right angles to the one above it.
The construction makes plywood
exceptionally strong both across and along the grain and reduces the natural
tendency of the wood to warp and shrink with atmospheric changes.
LAMINATE
Manufactured wood.
It is built of several thin pieces
that are glued together to form a single board. All the pieces run in the same
direction and the pieces are usually of the same thickness.
CANE
Bamboo bark that has been cut into
thin strips and woven into a web.
The design of the weave may be the
traditional hexagonal style or a variation in the contemporary basket, small
square, or rectangular shapes.
JOINTS
AND JOINT SUPPORTS
A JOINT is the permanent fastening
of two surfaces together. The several types of joints used for wood
construction are the butt, edge, rabbet, dado, lap, miter, mortise-and-tenon,
and dovetail.
BUTT or PLAIN JOINTS have the
square end of one piece fitted against the flat edge of the second piece. This
joint is a very weak joint. Added strength may
be supplied by a corner blocks and dowels.
EDGE JOINTS fasten pieces of wood
together side-by-side. The grain of both parts runs parallel, but the annual
rings should fall in opposite directions.
RABBET JOINTS are made by fitting
one piece into the L-shaped groove cut into the other piece.
LUMBER
CUTTING
The way lumber is cut from a log
determines the final appearance of the grain pattern.
There are three ways solid stock is
cut from a log
plain sawing (also called flat
sawing)
quarter sawing
rift sawing.
Plain sawing makes the most
efficient use of the log and is the least expensive of the three methods,
Because the wood is cut with various orientations to the grain of the tree,
plain sawing results in a finished surface with the characteristic cathedral
pattern.
Quarter sawing is produced
by cutting the log into quarters and then sawing perpendicular to a diameter
line. Because the saw cut is nearly perpendicular to the grain, the resulting
grain pattern more uniformly vertical. Quarter sawn boards tend
to twist and cup less, shrink less in width, hold
paint better, and have fewer defects than plain sawn boards.
Rift sawing provides an even
more consistent vertical grain because the saw cuts
are always made radially to the center of the tree. Because the log must e
shifted after each cut and because there is much e, rift cutting is more
expensive than quarter sawn and is seldom used.
Because of the limited availability
of some species of wood and the expense of making certain cuts, not all types
of lumber cutting are available in all species. The availability of cuts in
the desired species should be verified before specifications are written.
Types
of Veneer Cuts
There are five principal methods of
cutting veneers.
Plain slicing and quarter
slicing are accomplished the same way as cutting solid stock, except the
resulting pieces are much thinner.
Quarter slicing produces a
more straight-grained pattern than plain slicing because the cutting knife
strikes the growth rings at approximately a 90-degree angle.
With rotary slicing, the
log is mounted on a lathe and turned against a knife, which peels off a
continuous layer of veneer. This produces
the most veneer with the least waste.
Half-round slicing is
similar to rotary slicing, but the log is cut in half and the veneer cut
slightly across the annular growth rings. This results in a pronounced grain
pattern showing characteristics of both rotary-sliced and plain-sliced
veneers.
Rift slicing is
accomplished by quartering a log and cutting at a 15-degree angle to the
growth rings. Like quarter slicing, it results in a straight-grain pattern
and is commonly used with oak to eliminate the appearance of markings
perpendicular to the direction of the grain. These markings in oak are
caused by medullary rays, which are radial cells extending from the center
of the tree to its circumference.
When individual
veneers come from the same piece of log it is called a flitch.
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