A brief explanation of timber.
Timber is simply a hard, fibrous tissue found in the stems and root of
trees and other
woody plants. It has been used for thousands of years for both
fuel and as a construction material. It is an organic material, a natural
composite of
cellulose fibers (which are strong in tension) embedded in a
matrix of
lignin which resists compression. Wood is sometimes defined as only the secondary
xylem in the stems of trees,
or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs.
In a living tree it performs a support function, enabling woody plants
to grow large or to stand up by themselves. It also mediates the
transfer of water and
nutrients to the
leaves
and other growing tissues. Wood may also refer to other plant materials
with comparable properties, and to material engineered from wood, or
wood chips or fiber.
The entire timber refining process can be summarized into four parts as seen in the chart below
Hard and soft woods
There is a strong relationship between the properties of wood and the
properties of the particular tree that yielded it. The density of wood
varies with species. The density of a wood correlates with its strength
(mechanical properties). For example,
mahogany is a medium-dense hardwood that is excellent for fine furniture crafting, whereas
balsa is light, making it useful for
model building. One of the densest woods is
black ironwood.
It is common to classify wood as either
softwood or
hardwood. The wood from
conifers (e.g. pine) is called softwood, and the wood from
dicotyledons
(usually broad-leaved trees, e.g. oak) is called hardwood. These names
are a bit misleading, as hardwoods are not necessarily hard, and
softwoods are not necessarily soft. The well-known balsa (a hardwood) is
actually softer than any commercial softwood. Conversely, some
softwoods (e.g.
yew) are harder than many hardwoods.
Uses
Fuel
Wood has a long history of being used as fuel, which continues to
this day, mostly in rural areas of the world. Hardwood is preferred over
softwood because it creates less smoke and burns longer. Adding a
woodstove or fireplace to a home is often felt to add ambiance and
warmth. Nowadays, wood and pellets have become one of the most important
heating fuels for homes in USA, with an increase of approx. 34% over
the last decade.
[18]
Construction
Wood has been an important construction material since humans began
building shelters, houses and boats. Nearly all boats were made out of
wood until the late 19th century, and wood remains in common use today
in boat construction.
Elm
in particular was used for this purpose as it resisted decay as long as
it was kept wet (it also served for water pipe before the advent of
more modern plumbing).
Wood to be used for construction work is commonly known as
lumber in North America. Elsewhere,
lumber usually refers to felled trees, and the word for sawn planks ready for use is
timber. In Medieval Europe
oak
was the wood of choice for all wood construction, including beams,
walls, doors, and floors. Today a wider variety of woods is used: solid
wood doors are often made from
poplar, small-knotted
pine, and
Douglas fir.
New domestic housing in many parts of the world today is commonly made from timber-framed construction.
Engineered wood
products are becoming a bigger part of the construction industry. They
may be used in both residential and commercial buildings as structural
and aesthetic materials.
In buildings made of other materials, wood will still be found as a
supporting material, especially in roof construction, in interior doors
and their frames, and as exterior cladding.
Wood is also commonly used as shuttering material to form the mould into which concrete is poured during
reinforced concrete construction.
Engineered wood
Wood can be cut into straight planks and made into a
wood flooring.
Engineered wood products, glued building products "engineered" for
application-specific performance requirements, are often used in
construction and industrial applications. Glued engineered wood products
are manufactured by bonding together wood strands, veneers, lumber or
other forms of wood fiber with glue to form a larger, more efficient
composite structural unit.
[20]
These products include
glued laminated timber (glulam), wood structural panels (including
plywood,
oriented strand board and composite panels),
laminated veneer lumber (LVL) and other structural composite lumber (SCL) products,
parallel strand lumber, and I-joists.
[20] Approximately 100 million cubic meters of wood was consumed for this purpose in 1991.
[2] The trends suggest that particle board and fiber board will overtake plywood.
Wood unsuitable for construction in its native form may be broken
down mechanically (into fibers or chips) or chemically (into cellulose)
and used as a raw material for other building materials, such as
engineered wood, as well as
chipboard,
hardboard, and
medium-density fiberboard
(MDF). Such wood derivatives are widely used: wood fibers are an
important component of most paper, and cellulose is used as a component
of some
synthetic materials. Wood derivatives can also be used for kinds of flooring, for example
laminate flooring.
Furniture and utensils
Wood has always been used extensively for furniture, such as
chairs and beds. Also for tool handles and cutlery, such as
chopsticks,
toothpicks, and other utensils, like the
wooden spoon.
Next generation wood products
Further developments include new
lignin
glue applications, recyclable food packaging, rubber tire replacement
applications, anti-bacterial medical agents, and high strength fabrics
or composites.
[21]
As scientists and engineers further learn and develop new techniques to
extract various components from wood, or alternatively to modify wood,
for example by adding components to wood, new more advanced products
will appear on the marketplace. Moisture content electronic monitoring
can also enhance next generation wood protection.
[22]
In the arts
Wood has long been used as an
artistic medium. It has been used to make sculptures and
carvings for millennia. Examples include the
totem poles carved by North American indigenous people from conifer trunks, often Western Red Cedar (
Thuja plicata), and the Millennium clock tower,
[23] now housed in the
National Museum of Scotland in
Edinburgh.
It is also used in
woodcut printmaking, and for
engraving.
Certain types of
musical instruments, such as those of the
violin family, the guitar, the
clarinet and
recorder, the
xylophone, and the
marimba,
are made mostly or entirely of wood. The choice of wood may make a
significant difference to the tone and resonant qualities of the
instrument, and
tonewoods have widely differing properties, ranging from the hard and dense
african blackwood (used for the bodies of clarinets) to the light but resonant European spruce (
Picea abies) (traditionally used for the soundboards of violins). The most valuable tonewoods, such as the ripple sycamore (
Acer pseudoplatanus),
used for the backs of violins, combine acoustic properties with
decorative color and grain which enhance the appearance of the finished
instrument.
Despite their collective name, not all woodwind instruments are made entirely of wood. The
reeds used to play them, however, are usually made from
Arundo donax, a type of
monocot cane plant.
Sports and recreational equipment
Many types of
sports equipment are made of wood, or were constructed of wood in the past. For example,
cricket bats are typically made of
white willow. The
baseball bats which are legal for use in
Major League Baseball are frequently made of
ash wood or
hickory, and in recent years have been constructed from
maple even though that wood is somewhat more fragile. In
softball, however, bats are more commonly made of
aluminium (this is especially true for
fastpitch softball). NBA courts have been traditionally made out of
hardwood,Main article:
Parquetry#Use in the NBA.
Many other types of sports and recreation equipment, such as
skis,
ice hockey sticks,
lacrosse sticks and
archery bows, were commonly made of wood in the past, but have since been replaced with more modern materials such as aluminium,
fiberglass,
carbon fiber,
titanium, and
composite materials. One noteworthy example of this trend is the
golf club commonly known as the
wood, the head of which was traditionally made of
persimmon wood in the early days of the game of golf, but is now generally made of synthetic materials.
Medicine
In January 2010 Italian scientists announced that wood could be harnessed to become a
bone substitute. It is likely to take at least five years until this technique will be applied for humans.
