Wood surface, showing several features

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of 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,^[1] or it is defined more broadly to include the same type of tissue elsewhere such as in tree roots or in other plants such as shrubs.^{[citation needed]} In a living tree it performs a support function, enabling woody plants to grow large or to stand up for 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 earth contains about one trillion tonnes of wood, which grows at a rate of 10 billion tonnes per year. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991, approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction.^[2]

History[link]

A 2011 discovery in the Canadian province of New Brunswick uncovered the earliest known plants to have grown wood, approximately 395 to 400 million years ago.^[3]

People have used wood for millennia for many purposes, primarily as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and paper.

Wood can be dated by carbon dating and in some species by dendrochronology to make inferences about when a wooden object was created.

The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at that time.^[4]

Physical properties[link]

Growth rings[link]

Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. This process is known as secondary growth; it is the result of cell division in the vascular cambium, a lateral meristem, and subsequent expansion of the new cells. Where there are clear seasons, growth can occur in a discrete annual or seasonal pattern, leading to growth rings; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If these seasons are annual these growth rings are referred to as annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.

If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood.^[5] However, there are major differences, depending on the kind of wood (see below).

Knots[link]

A knot on a tree at the Garden of the Gods public park in Colorado Springs, Colorado (October 2006)

A knot is a particular type of imperfection in a piece of wood; it will affect the technical properties of the wood, usually for the worse, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood.

In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.

During the development of a tree, the lower limbs often die, but may remain attached for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.

In grading lumber and structural timber, knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.

Wood Knot

Knots materially affect cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than where under load along the grain and/or compression. The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots, however, may be located along the neutral plane of a beam and increase the strength by preventing longitudinal shearing. Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects.^[6]

Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.

In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted, such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution, correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.

Heartwood and sapwood[link]

A section of a Yew branch showing 27 annual growth rings, pale sapwood and dark heartwood, and pith (centre dark spot). The dark radial lines are small knots.

Heartwood (or duramen^[7]) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation occurs spontaneously (it is a genetically programmed process). Once heartwood formation is complete, the heartwood is dead.^[8] Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once.^[9]

Usually heartwood looks different; in that case it can be seen on a cross-section, usually following the growth rings in shape. Heartwood may (or may not) be much darker than living wood. It may (or may not) be sharply distinct from the sapwood. However, other processes, such as decay, can discolor wood, even in woody plants that do not form heartwood, with a similar color difference, which may lead to confusion.

Sapwood (or alburnum^[7]) is the younger, outermost wood; in the growing tree it is living wood,^[8] and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees (of species that do form heartwood) grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines.

The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. Others never form heartwood.

No definite relation exists between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.

When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.

It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds, and in a few instances thousands, of years old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bore into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position.

If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.

Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.

Color[link]

In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color difference does not mean a dramatic difference in the mechanical properties of heartwood and sapwood, although there may be a dramatic chemical difference.

Some experiments on very resinous Longleaf Pine specimens indicate an increase in strength, due to the resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.

The wood of Coast Redwood is distinctively red in color

Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.

Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as spalting produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect.

Water content[link]

Water occurs in living wood in three conditions, namely: (1) in the cell walls, (2) in the protoplasmic contents of the cells, and (3) as free water in the cell cavities and spaces. In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.

The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on paper or cloth. Within certain limits, the greater the water content, the greater its softening effect.

Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of the same size will.^{[citation needed]}

The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected.

Structure[link]

Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It is composed of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).^[10]

Sections of tree trunk

A tree trunk as found at the Veluwe, Netherlands

In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.

The structure of hardwoods is more complex.^[11] The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous. In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fiber are the elements which give strength and toughness to wood, while the vessels are a source of weakness.

Magnified cross-section of Black Walnut, showing the vessels, rays (white lines) and annual rings: this is intermediate between diffuse-porous and ring-porous, with vessel size declining gradually

In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are basswood, birch, buckeye, maple, poplar, and willow. Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.

Earlywood and latewood in softwood[link]

earlywood and latewood in a softwood; radial view, growth rings closely spaced in a Pseudotsuga taxifolia

In temperate softwoods there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater the proportion of latewood the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring.

If a heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.

It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain but little. One can judge comparative density, and therefore to some extent strength, by visual inspection.

No satisfactory explanation can as yet be given for the exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen.

Earlywood and latewood in ring-porous woods[link]

Earlywood and latewood in a ring-porous wood (ash) in a Fraxinus excelsior ; tangential view, wide growth rings

In ring-porous woods each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before.

In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.

In ring-porous woods of good growth it is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.

Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in a closed forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:

"The work or shock-resisting ability is greatest in wide-ringed wood that has from 5 to 14 rings per inch (rings 1.8-5 mm thick), is fairly constant from 14 to 38 rings per inch (rings 0.7–1.8 mm thick), and decreases rapidly from 38 to 47 rings per inch (rings 0.5–0.7 mm thick). The strength at maximum load is not so great with the most rapid-growing wood; it is maximum with from 14 to 20 rings per inch (rings 1.3–1.8 mm thick), and again becomes less as the wood becomes more closely ringed. The natural deduction is that wood of first-class mechanical value shows from 5 to 20 rings per inch (rings 1.3–5 mm thick) and that slower growth yields poorer stock. Thus the inspector or buyer of hickory should discriminate against timber that has more than 20 rings per inch (rings less than 1.3 mm thick). Exceptions exist, however, in the case of normal growth upon dry situations, in which the slow-growing material may be strong and tough."^[12]

The effect of rate of growth on the qualities of chestnut wood is summarised by the same authority as follows:

"When the rings are wide, the transition from spring wood to summer wood is gradual, while in the narrow rings the spring wood passes into summer wood abruptly. The width of the spring wood changes but little with the width of the annual ring, so that the narrowing or broadening of the annual ring is always at the expense of the summer wood. The narrow vessels of the summer wood make it richer in wood substance than the spring wood composed of wide vessels. Therefore, rapid-growing specimens with wide rings have more wood substance than slow-growing trees with narrow rings. Since the more the wood substance the greater the weight, and the greater the weight the stronger the wood, chestnuts with wide rings must have stronger wood than chestnuts with narrow rings. This agrees with the accepted view that sprouts (which always have wide rings) yield better and stronger wood than seedling chestnuts, which grow more slowly in diameter."^[12]

Earlywood and latewood in diffuse-porous woods[link]

In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye. Conversely, when there is a clear demarcation there may not be a noticeable difference in structure within the growth ring.

In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the conifers. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, total strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of grain, which will in most cases occur when there is little contrast between the latewood of one season's growth and the earlywood of the next.

Monocot wood[link]

Trunks of the Coconut palm, a monocot, in Java. From this perspective these look not much different from trunks of a dicot or conifer

Structural material that roughly (in its gross handling characteristics) resembles ordinary, "dicot" or conifer wood is produced by a number of monocot plants, and these also are colloquially called wood. Of these, bamboo, botanically a member of the grass family, has considerable economic importance, larger culms being widely used as a building and construction material in their own right and, these days, in the manufacture of engineered flooring, panels and veneer. Another major plant group that produce material that often is called wood are the palms. Of much less importance are plants such as Pandanus, Dracaena and Cordyline. With all this material, the structure and composition of the structural material is quite different from ordinary wood.

Hard and soft woods[link]

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.

Chemistry of wood[link]

Aside from water, wood has three main components. Cellulose, a crystalline polymer derived from glucose, constitutes about 41–43%. Next in abundance is hemicellulose, which is around 20% in deciduous trees but near 30% in conifers. It is mainly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third component at around 27% in coniferous wood vs 23% in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between the lignin and the hemicellulose. A major focus of the paper industry is the separation of the lignin from the cellulose, from which paper is made.

Chemical structure of lignin, which comprises approximately 30% of wood and is responsible for many of its properties.

In chemical terms, the difference between hardwood and softwood is reflected in the composition of the constituent lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is mainly derived from coniferyl alcohol.^[13]

Extractives[link]

Aside from the lignocellulose, wood consists of a variety of low molecular weight organic compounds, called extractives. The wood extractives are fatty acids, resin acids, waxes and terpenes.^[14] For example, rosin is exuded by conifers as protection from insects. The extraction of these organic materials from wood provides tall oil, terpentine, and rosin.^[15]

Uses[link]

Fuel[link]

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.^[16]

The churches of Kizhi, Russia are among a handful of World Heritage Sites built entirely of wood, without metal joints. See Kizhi Pogost for more details.

The complex carpentry of the Centre Pompidou-Metz museum, Metz.

Construction[link]

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.

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.

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.

Furniture and utensils[link]

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.

Engineered wood[link]

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.^[18] 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.^[18] 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.

Engineered wood products display highly predictable and reliable performance characteristics and provide enhanced design flexibility: on one hand, these products allow the use of smaller pieces, and on the other hand, they allow for bigger spans. They may also be selected for specific projects such as public swimming pools or ice rinks where the wood will not deteriorate in the presence of certain chemicals, and are less susceptible to the humidity changes commonly found in these environments.

Engineered wood products prove to be more environmentally friendly and, if used appropriately, are often less expensive than building materials such as steel or concrete. These products are extremely resource-efficient because they use more of the available resource with minimal waste. In most cases, engineered wood products are produced using faster growing and often underutilized wood species from managed forests and tree farms.^[19]

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.

Next generation wood products[link]

Further developments include new lignin glue applications, recyclable food packaging, rubber tire replacement applications, anti-bacterial medical agents, and high strength fabrics or composites.^[20] 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.

In the arts[link]

Artists can use wood to create delicate sculptures.

Stringed instrument bows are often made from pernambuco or brazilwood.

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,^[21] now housed in the National Museum of Scotland^[22] 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[link]

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).

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[link]

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.^[23]

See also[link]

Notes[link]

References[link]

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Elijah Wood
Elijah Wood at the San Diego Comic-Con International in July 2011.
Born	Elijah Jordan Wood (1981-01-28) January 28, 1981 (age 31) Cedar Rapids, Iowa, US
Occupation	Actor
Years active	1989–present

Elijah Jordan Wood ( /ɪˈlaɪdʒə ˈdʒɔrdən ˈwʊd/; born January 28, 1981) is an American actor. He made his film debut with a minor part in Back to the Future Part II (1989), then landed a succession of larger roles that made him a critically acclaimed child actor by age 9, being nominated for several Young Artist Awards. He is best known for his high-profile role as Frodo Baggins in Peter Jackson's critically acclaimed The Lord of the Rings trilogy and its upcoming prequels The Hobbit films. Since then, he has resisted typecasting by choosing varied roles in critically acclaimed films such as Bobby, Eternal Sunshine of the Spotless Mind, Sin City, Green Street and Everything Is Illuminated.

Wood starred in the film Day Zero (2007) and provided the voice of the main character in the award-winning animated musical films Happy Feet and Happy Feet Two. Wood also voiced the lead as 9 in the Tim Burton-produced action/science fiction film 9. He played an American tourist turned vampire in Paris, je t'aime. In 2005, he started his own record label, Simian Records. He currently appears as Ryan in FX's dark comedy Wilfred, which debuted on June 23, 2011.

Early life[link]

Wood, the second of three children, was born and raised in Cedar Rapids, Iowa to Debra D. (née Krause) and Warren W. Wood, delicatessen operators.^[1] He is of English, German, Austrian, and Danish descent.^[2] Wood has a brother, Zachariah "Zach" Wood, and a sister, Hannah Wood. At age ten, Wood began modeling in his hometown and took piano lessons. He took to the stage in his elementary school's staging of the play The Sound of Music. The following year, he graduated to the title character in The Wonderful Wizard of Oz. He also served as choir boy during the production of See How They Run, produced by the Marion Creative Council.

Career[link]

Early career 1988-1998[link]

Wood modeled and did local commercials before moving with his family to Los Angeles in 1988, where he got his first break, a small role in a video by Paula Abdul – "Forever Your Girl", directed by David Fincher. More work followed, including a pivotal role in the television movie Child in the Night (1990) with JoBeth Williams and Tom Skerritt and a minor role in Back to the Future Part II (1989). It was Wood's role as Aidan Quinn's son in Barry Levinson's 1990 film Avalon (the third film in the Baltimore trilogy containing 1982's Diner and 1987's Tin Men) that first gave Wood attention, as the film received widespread critical acclaim and was nominated for four Academy Awards.

After a small part in the Richard Gere movie Internal Affairs (1990), he secured his first starring role in Paradise (1991), playing a young boy who brings estranged couple Melanie Griffith and Don Johnson back together. From there, he went on to co-star with Mel Gibson and Jamie Lee Curtis in Forever Young and with Joseph Mazzello in Radio Flyer (both were released in 1992).

In 1993, he had the lead role in The Adventures of Huck Finn and also appeared with Macaulay Culkin in The Good Son. In 1994 he starred in The War (1994), with Kevin Costner. His performance in this movie gained him a nomination for a 'Young Star Award' (for which he was nominated four times, and won twice), and Roger Ebert said in his review of the film:

"Elijah Wood has emerged, I believe, as the most talented actor, in his age group, in Hollywood history".^[3]

Also in 1994, he had the title role in North, and was featured in a Super Bowl commercial for Wavy Lay's potato chips that had him repeatedly exchanging seats with spectators at a football game (including Dan Quayle) using its famous slogan.^[4] In 1995, he appeared in the music video for The Cranberries "Ridiculous Thoughts". The following year, Wood got the lead role in Flipper (1996), which was not very successful, but the subsequent critical and financial success of Ang Lee's The Ice Storm (1997) provided a positive development in the young actor's career.

In 1997, he portrayed the pick-pocketing thief Jack "The Artful Dodger" Dawkins in Tony Bill's Oliver Twist. 1998's Deep Impact and The Faculty did not allow Wood the same degree of character development, but were great financial successes and further stepping stones in Wood's evolution from child star to young actor.

Wood's next role was as the boyfriend of a wannabe hip-hop groupie in James Toback's Black and White (1999). He followed this with a role as a junior hitman in Chain of Fools.

[edit] 1999–2003: The Lord of the Rings

Wood was cast as Frodo Baggins in The Lord of the Rings: The Fellowship of the Ring, the first installment of director Peter Jackson's adaptation of J.R.R. Tolkien's novel. His most hotly anticipated project, the 2001 film gave Wood top billing as Baggins, alongside a cast that included Ian McKellen, Liv Tyler, Orlando Bloom, Cate Blanchett, Christopher Lee, Sean Bean, Sean Astin, Billy Boyd, Dominic Monaghan, Viggo Mortensen, John Rhys-Davies, Miranda Otto, Karl Urban.

The Lord of the Rings was filmed in New Zealand and, before the cast left the country, Jackson gave Wood two gifts: one of the One Ring props used on the set and Sting, Frodo's sword. He was also given a pair of prosthetic "hobbit feet" which were worn during filming. The same year, the actor appeared in Ed Burns' Ash Wednesday, a crime drama that also featured Oliver Platt and Rosario Dawson.

In 2002, Wood lent his voice to the direct-to-video release of The Adventures of Tom Thumb and Thumbelina. His most substantial role of 2002 was his return to the role of Frodo Baggins in The Lord of the Rings: The Two Towers.

In 2003, he starred in the direct-to-video movie All I Want (also titled Try Seventeen) and once again portrayed Frodo Baggins for The Lord of the Rings: The Return of the King, the final part of Jackson's trilogy.

He is set to reprise his role as Frodo in the 2012 up-coming film The Hobbit: An Unexpected Journey.

2004–present: Recent career[link]

Hot on the heels of the trilogy, Wood quickly appeared in his first post-Frodo role in Eternal Sunshine of the Spotless Mind (2004), playing a lab technician who helps erase heartbreaking memories but then uses his knowledge of the past relationship of an unknowing former patient (Kate Winslet) to woo her. He then played bespectacled serial killer Kevin in director Robert Rodriguez and writer-artist Frank Miller's adaptation of Miller's crime noir comic book series Sin City (2005), appearing opposite Mickey Rourke in the segment "The Hard Goodbye". On May 12, 2005, Wood hosted a program called "MTV Presents: The Next Generation Xbox Revealed", when the new Xbox 360 games console was launched.^[5]

Also in 2005, Wood starred in Everything Is Illuminated, in which he plays a young American Jewish man on a quest to find the woman who once saved his grandfather during World War II, and Green Street Hooligans, as an American college student who falls in with a violent English football firm. Both had limited release, but were critically acclaimed.

Wood shot a small part in Paris, je t'aime, which consists of 18 five-minute sections. Each section is directed by a different director. Wood’s section, called "Quartier de la Madeleine", was directed by Vincenzo Natali. The film opened on May 18 at the 2006 Cannes Film Festival and was shown at 2006 Toronto International Film Festival. First Look Pictures acquired the North American rights, and the film opened in the US in early 2007.^[6]

In 2006, he was part of the ensemble cast in Emilio Estevez's Bobby, in which his character gets married to change his draft classification.^[7] It premiered at the Venice Film Festival and was released on November 17, 2006, in New York and Los Angeles. Wide release followed on November 23.

In Happy Feet,^[8] Wood provided the voice of Mumble, a penguin who can tap dance, but not sing. Happy Feet was released on November 17, 2006, and has grossed over $380 million worldwide. The movie also received a Golden Globe Award nomination and won an Academy Award and a BAFTA for Best Animated Feature.

Day Zero,^[9] a drama about the draft, had its debut at the 2007 Tribeca Film Festival. Wood portrays draftee Aaron Feller.

In 2006, Wood hosted the special "Saving a Species: The Great Penguin Rescue" for Discovery Kids Channel,^[10] for which he has been nominated for a Daytime Emmy in the category of acting in a children/youth/family special.^[11] On January 4, 2007, Wood joined Screen Actors Guild President Alan Rosenberg to announce the nominees for the 13th Annual Screen Actors Guild Awards.^[12]

In The Oxford Murders, a film adaptation of the novel of the same name by Guillermo Martínez, Wood plays a graduate student who investigates a series of bizarre, mathematically-based murders in Oxford.^[13][14] It was released in Spain on January 18, 2008.

Wood at WonderCon 2009.

Wood also voiced the lead in the animated feature film version of the short film 9.^[15][16] A project in which Wood was set to star in, a biopic about singer Iggy Pop, putatively named The Passenger,^[17] has not come to fruition after years in development.^[18]

Wood's first starring TV role is on the FX series Wilfred in which he plays Ryan. The pilot was shot in the summer of 2010.^[19]

In January 2011, it was confirmed that Wood would reprise the role of Frodo Baggins in the The Hobbit parts one and two films to be released in 2012 and 2013.^[20]

Wood also starred in The Beastie Boys music video for Make Some Noise, along with Seth Rogen and Danny McBride.

Other work[link]

Wood DJ'ing at the box.com launch party in New York in 2012

In 2005 Wood started his own record label called Simian Records. On September 19, 2006, Wood announced that Simian had signed The Apples in Stereo as their first band, with their new album New Magnetic Wonder released in February 2007.^[21] In addition he also directed the music video for "Energy".^[22] The other band signed to Simian thus far is Heloise and the Savoir Faire.

Wood has also provided voiceovers for videogames, providing the current voice for Spyro the Dragon since 2006's The Legend of Spyro: A New Beginning,^[23][24] as well as reprising Mumble in the game version of Happy Feet.^[25] He also contributed his talents to fellow Lord of the Rings star Viggo Mortensen's album Pandemoniumfromamerica, singing and playing various instruments on the album.^[26]

Wood has signed to co-produce the film Black Wings Has My Angel, based on the noir novel of the same name, with Anthony Moody and Rob Malkani of Indalo Productions.^[27]

On April 11, 2008, Wood was the guest host of Channel 4's Friday Night Project.

On April 25, 2009, Wood was honored with the Midnight Award by the San Francisco International Film Festival as a dynamic young American actor who "has made outstanding contributions to independent and Hollywood cinema, and who brings striking intelligence, exemplary talent and extraordinary depth of character to his roles"^{[citation needed]}.^[28] Wood also starred in an episode of Yo! Gabba Gabba entitled "Eat" where he danced and "went crazy" alongside the rest of the Yo! Gabba Gabba crew. Wood can be seen in a short film on stepthroughtheportal.com. The site is an interactive website created by Simian Records artist' The Apples in Stereo, promoting their upcoming album, Travelers in Space and Time. At PAX East in April 2012, it was confirmed that Wood will give the voice to Agent Maine/The Meta's AI, Sigma, in Season 10 of Red vs. Blue.

Wood in February 2006

Wood has also expressed his interest in pursuing a career in the music industry, with desires to both start his own record label and to DJ under the name 'DJ Frodo'.^{[citation needed]}

Personal life[link]

Elijah Wood is the older brother of actress Hannah Wood.

In an interview about Everything Is Illuminated, director Liev Schreiber commented that Wood has a "generosity of spirit" and a "sincere goodness as a human being."^[29] He supported campaigns for charity as Keep a Child Alive or ALDO/YouthAIDS. Wood is a music lover, owning 4,000 CDs and at one time citing his favorite band as Smashing Pumpkins.^[30][31]

Wood has a tattoo of the word "nine" written in Tengwar script, but in the English language (rather than Quenya or Sindarin as is widely believed) below his waist on the right side, a reference to his character as one of the Fellowship of the Ring. This is somewhat of a coincidence, as he would later star in 9. The other actors of "The Fellowship" got the same tattoo with the exception of John Rhys-Davies. Rhys-Davies's stunt double from the film got the tattoo instead, thus the cast can still assert that "all" the members of the Fellowship acquired a tattoo.^[32]

In May 2006, Autograph Collector Magazine published its list of 10 Best & 10 Worst Hollywood Autograph Signers, Wood was ranked #7 of Best Signers.^[33]

On April 23, 2010, in a charitable gesture, Wood visited the town of Curepto, Chile, one of the hardest hit by the 8.8 magnitude earthquake that struck Chile on February 27, 2010. He made personal visits to many of the victims and was accompanied by the first lady of Chile, Ms. Cecilia Morel.^[34][35]

In 2008, he became the first person to cross Victoria Falls on ropes during an appearance on Jack Osbourne's show Adrenaline Junkie.^[36]

Filmography[link]

Films[link]