AskDefine | Define wood

The Collaborative Dictionary

Wood \Wood\, v. i. To grow mad; to act like a madman; to mad. --Chaucer. [1913 Webster]
Wood \Wood\, n. [OE. wode, wude, AS. wudu, wiodu; akin to OHG. witu, Icel. vi?r, Dan. & Sw. ved wood, and probably to Ir. & Gael. fiodh, W. gwydd trees, shrubs.] [1913 Webster]
A large and thick collection of trees; a forest or grove; -- frequently used in the plural. [1913 Webster] Light thickens, and the crow Makes wing to the rooky wood. --Shak. [1913 Webster]
The substance of trees and the like; the hard fibrous substance which composes the body of a tree and its branches, and which is covered by the bark; timber. "To worship their own work in wood and stone for gods." --Milton. [1913 Webster]
(Bot.) The fibrous material which makes up the greater part of the stems and branches of trees and shrubby plants, and is found to a less extent in herbaceous stems. It consists of elongated tubular or needle-shaped cells of various kinds, usually interwoven with the shinning bands called silver grain. [1913 Webster] Note: Wood consists chiefly of the carbohydrates cellulose and lignin, which are isomeric with starch. [1913 Webster]
Trees cut or sawed for the fire or other uses. [1913 Webster] Wood acid, Wood vinegar (Chem.), a complex acid liquid obtained in the dry distillation of wood, and containing large quantities of acetic acid; hence, specifically, acetic acid. Formerly called pyroligneous acid. Wood anemone (Bot.), a delicate flower (Anemone nemorosa) of early spring; -- also called windflower. See Illust. of Anemone. Wood ant (Zool.), a large ant (Formica rufa) which lives in woods and forests, and constructs large nests. Wood apple (Bot.). See Elephant apple, under Elephant. Wood baboon (Zool.), the drill. Wood betony. (Bot.) (a) Same as Betony. (b) The common American lousewort (Pedicularis Canadensis), a low perennial herb with yellowish or purplish flowers. Wood borer. (Zool.) (a) The larva of any one of numerous species of boring beetles, esp. elaters, longicorn beetles, buprestidans, and certain weevils. See Apple borer, under Apple, and Pine weevil, under Pine. (b) The larva of any one of various species of lepidopterous insects, especially of the clearwing moths, as the peach-tree borer (see under Peach), and of the goat moths. (c) The larva of various species of hymenopterous of the tribe Urocerata. See Tremex. (d) Any one of several bivalve shells which bore in wood, as the teredos, and species of Xylophaga. (e) Any one of several species of small Crustacea, as the Limnoria, and the boring amphipod (Chelura terebrans). Wood carpet, a kind of floor covering made of thin pieces of wood secured to a flexible backing, as of cloth. --Knight. Wood cell (Bot.), a slender cylindrical or prismatic cell usually tapering to a point at both ends. It is the principal constituent of woody fiber. Wood choir, the choir, or chorus, of birds in the woods. [Poetic] --Coleridge. Wood coal, charcoal; also, lignite, or brown coal. Wood cricket (Zool.), a small European cricket (Nemobius sylvestris). Wood culver (Zool.), the wood pigeon. Wood cut, an engraving on wood; also, a print from such an engraving. Wood dove (Zool.), the stockdove. Wood drink, a decoction or infusion of medicinal woods. Wood duck (Zool.) (a) A very beautiful American duck (Aix sponsa). The male has a large crest, and its plumage is varied with green, purple, black, white, and red. It builds its nest in trees, whence the name. Called also bridal duck, summer duck, and wood widgeon. (b) The hooded merganser. (c) The Australian maned goose (Chlamydochen jubata). Wood echo, an echo from the wood. Wood engraver. (a) An engraver on wood. (b) (Zool.) Any of several species of small beetles whose larvae bore beneath the bark of trees, and excavate furrows in the wood often more or less resembling coarse engravings; especially, Xyleborus xylographus. Wood engraving. (a) The act or art engraving on wood; xylography. (b) An engraving on wood; a wood cut; also, a print from such an engraving. Wood fern. (Bot.) See Shield fern, under Shield. Wood fiber. (a) (Bot.) Fibrovascular tissue. (b) Wood comminuted, and reduced to a powdery or dusty mass. Wood fretter (Zool.), any one of numerous species of beetles whose larvae bore in the wood, or beneath the bark, of trees. Wood frog (Zool.), a common North American frog (Rana sylvatica) which lives chiefly in the woods, except during the breeding season. It is drab or yellowish brown, with a black stripe on each side of the head. Wood germander. (Bot.) See under Germander. Wood god, a fabled sylvan deity. Wood grass. (Bot.) See under Grass. Wood grouse. (Zool.) (a) The capercailzie. (b) The spruce partridge. See under Spruce. Wood guest (Zool.), the ringdove. [Prov. Eng.] Wood hen. (Zool.) (a) Any one of several species of Old World short-winged rails of the genus Ocydromus, including the weka and allied species. (b) The American woodcock. Wood hoopoe (Zool.), any one of several species of Old World arboreal birds belonging to Irrisor and allied genera. They are closely allied to the common hoopoe, but have a curved beak, and a longer tail. Wood ibis (Zool.), any one of several species of large, long-legged, wading birds belonging to the genus Tantalus. The head and neck are naked or scantily covered with feathers. The American wood ibis (Tantalus loculator) is common in Florida. Wood lark (Zool.), a small European lark (Alauda arborea), which, like, the skylark, utters its notes while on the wing. So called from its habit of perching on trees. Wood laurel (Bot.), a European evergreen shrub (Daphne Laureola). Wood leopard (Zool.), a European spotted moth (Zeuzera aesculi) allied to the goat moth. Its large fleshy larva bores in the wood of the apple, pear, and other fruit trees. Wood lily (Bot.), the lily of the valley. Wood lock (Naut.), a piece of wood close fitted and sheathed with copper, in the throating or score of the pintle, to keep the rudder from rising. Wood louse (Zool.) (a) Any one of numerous species of terrestrial isopod Crustacea belonging to Oniscus, Armadillo, and related genera. See Sow bug, under Sow, and Pill bug, under Pill. (b) Any one of several species of small, wingless, pseudoneuropterous insects of the family Psocidae, which live in the crevices of walls and among old books and papers. Some of the species are called also book lice, and deathticks, or deathwatches. Wood mite (Zool.), any one of numerous small mites of the family Oribatidae. They are found chiefly in woods, on tree trunks and stones. Wood mote. (Eng. Law) (a) Formerly, the forest court. (b) The court of attachment. Wood nettle. (Bot.) See under Nettle. Wood nightshade (Bot.), woody nightshade. Wood nut (Bot.), the filbert. Wood nymph. (a) A nymph inhabiting the woods; a fabled goddess of the woods; a dryad. "The wood nymphs, decked with daisies trim." --Milton. (b) (Zool.) Any one of several species of handsomely colored moths belonging to the genus Eudryas. The larvae are bright-colored, and some of the species, as Eudryas grata, and Eudryas unio, feed on the leaves of the grapevine. (c) (Zool.) Any one of several species of handsomely colored South American humming birds belonging to the genus Thalurania. The males are bright blue, or green and blue. Wood offering, wood burnt on the altar. [1913 Webster] We cast the lots . . . for the wood offering. --Neh. x.
[1913 Webster] Wood oil (Bot.), a resinous oil obtained from several East Indian trees of the genus Dipterocarpus, having properties similar to those of copaiba, and sometimes substituted for it. It is also used for mixing paint. See Gurjun. Wood opal (Min.), a striped variety of coarse opal, having some resemblance to wood. Wood paper, paper made of wood pulp. See Wood pulp, below. Wood pewee (Zool.), a North American tyrant flycatcher (Contopus virens). It closely resembles the pewee, but is smaller. Wood pie (Zool.), any black and white woodpecker, especially the European great spotted woodpecker. Wood pigeon. (Zool.) (a) Any one of numerous species of Old World pigeons belonging to Palumbus and allied genera of the family Columbidae. (b) The ringdove. Wood puceron (Zool.), a plant louse. Wood pulp (Technol.), vegetable fiber obtained from the poplar and other white woods, and so softened by digestion with a hot solution of alkali that it can be formed into sheet paper, etc. It is now produced on an immense scale. Wood quail (Zool.), any one of several species of East Indian crested quails belonging to Rollulus and allied genera, as the red-crested wood quail (Rollulus roulroul), the male of which is bright green, with a long crest of red hairlike feathers. Wood rabbit (Zool.), the cottontail. Wood rat (Zool.), any one of several species of American wild rats of the genus Neotoma found in the Southern United States; -- called also bush rat. The Florida wood rat (Neotoma Floridana) is the best-known species. Wood reed grass (Bot.), a tall grass (Cinna arundinacea) growing in moist woods. Wood reeve, the steward or overseer of a wood. [Eng.] Wood rush (Bot.), any plant of the genus Luzula, differing from the true rushes of the genus Juncus chiefly in having very few seeds in each capsule. Wood sage (Bot.), a name given to several labiate plants of the genus Teucrium. See Germander. Wood screw, a metal screw formed with a sharp thread, and usually with a slotted head, for insertion in wood. Wood sheldrake (Zool.), the hooded merganser. Wood shock (Zool.), the fisher. See Fisher,
Wood shrike (Zool.), any one of numerous species of Old World singing birds belonging to Grallina, Collyricincla, Prionops, and allied genera, common in India and Australia. They are allied to the true shrikes, but feed upon both insects and berries. Wood snipe. (Zool.) (a) The American woodcock. (b) An Asiatic snipe (Gallinago nemoricola). Wood soot, soot from burnt wood. Wood sore. (Zool.) See Cuckoo spit, under Cuckoo. Wood sorrel (Bot.), a plant of the genus Oxalis (Oxalis Acetosella), having an acid taste. See Illust. (a) of Shamrock. Wood spirit. (Chem.) See Methyl alcohol, under Methyl. Wood stamp, a carved or engraved block or stamp of wood, for impressing figures or colors on fabrics. Wood star (Zool.), any one of several species of small South American humming birds belonging to the genus Calothorax. The male has a brilliant gorget of blue, purple, and other colors. Wood sucker (Zool.), the yaffle. Wood swallow (Zool.), any one of numerous species of Old World passerine birds belonging to the genus Artamus and allied genera of the family Artamidae. They are common in the East Indies, Asia, and Australia. In form and habits they resemble swallows, but in structure they resemble shrikes. They are usually black above and white beneath. Wood tapper (Zool.), any woodpecker. Wood tar. See under Tar. Wood thrush, (Zool.) (a) An American thrush (Turdus mustelinus) noted for the sweetness of its song. See under Thrush. (b) The missel thrush. Wood tick. See in Vocabulary. Wood tin. (Min.). See Cassiterite. Wood titmouse (Zool.), the goldcgest. Wood tortoise (Zool.), the sculptured tortoise. See under Sculptured. Wood vine (Bot.), the white bryony. Wood vinegar. See Wood acid, above. Wood warbler. (Zool.) (a) Any one of numerous species of American warblers of the genus Dendroica. See Warbler. (b) A European warbler (Phylloscopus sibilatrix); -- called also green wren, wood wren, and yellow wren. Wood worm (Zool.), a larva that bores in wood; a wood borer. Wood wren. (Zool.) (a) The wood warbler. (b) The willow warbler. [1913 Webster]
Wood \Wood\ (w[oo^]d), a. [OE. wod, AS. w[=o]d; akin to OHG. wuot, Icel. [=o][eth]r, Goth. w[=o]ds, D. woede madness, G. wuth, wut, also to AS. w[=o][eth] song, Icel. [=o][eth]r, L. vates a seer, a poet. Cf. Wednesday.] Mad; insane; possessed; rabid; furious; frantic. [Obs.] [Written also wode.] [1913 Webster] Our hoste gan to swear as [if] he were wood. --Chaucer. [1913 Webster]
Wood \Wood\, v. t. [imp. & p. p. Wooded; p. pr. & vb. n. Wooding.] To supply with wood, or get supplies of wood for; as, to wood a steamboat or a locomotive. [1913 Webster] [1913 Webster]
Wood \Wood\, v. i. To take or get a supply of wood. [1913 Webster]

Word Net

wood

Noun

1 the hard fibrous lignified substance under the bark of trees
2 the trees and other plants in a large densely wooded area [syn: forest, woods]
3 United States film actress (1938-1981) [syn: Natalie Wood]
4 English conductor (1869-1944) [syn: Sir Henry Wood, Sir Henry Joseph Wood]
5 English writer of novels about murders and thefts and forgeries (1814-1887) [syn: Mrs. Henry Wood, Ellen Price Wood]
6 United States painter noted for works based on life in the Midwest (1892-1942) [syn: Grant Wood]
7 any wind instrument other than the brass instruments [syn: woodwind, woodwind instrument]
8 a golf club with a long shaft used to hit long shots; originally made with a wooden head; metal woods are now available

Moby Thesaurus

acacia, afforestation, alder, arboretum, ash, backlog, balsa, balsam, banyan, bass, basswood, bavin, beam, beech, beechwood, billet, birch, board, boarding, boondocks, brush, brushwood, burl, bush, bushveld, buttonwood, chase, cherry, chestnut, clapboard, climax forest, cloud forest, cord, cordwood, cork, cypress, deal, dendrology, dogwood, driftwood, ebony, elm, eucalyptus, fagot, fir, firewood, forest, forest land, forest preserve, forestry, fringing forest, gallery forest, greenwood, gum, gumwood, hanger, hardwood, hazel, hemlock, hickory, index forest, ironwood, jungle, jungles, juniper, kindling, kindlings, lancewood, larch, lath, lathing, lathwork, linden, locust, log, logwood, lumber, magnolia, mahogany, maple, national forest, oak, olive, palmetto barrens, panelboard, paneling, panelwork, park, park forest, pecan, pine, pine barrens, plank, planking, plyboard, plywood, pole, poplar, post, primeval forest, protection forest, puncheon, rain forest, redwood, reforestation, sandalwood, scrub, scrubland, selection forest, shake, sheathing, sheathing board, sheeting, shingle, shrubland, sideboard, siding, silviculture, slab, slat, softwood, splat, sprout forest, spruce, stand of timber, state forest, stave, stick, stick of wood, stovewood, sumac, sycamore, teak, three-by-four, timber, timbering, timberland, timberwork, tree veld, two-by-four, virgin forest, walnut, weatherboard, wildwood, woodland, woods, yew, yule clog, yule log
see Wood

English

Pronunciation

Homophones

Etymology 1

etyl ang wudu.

Noun

  1. The substance making up the central part of the trunk and branches of a tree. Used as a material for construction, to manufacture various items, etc. or as fuel.
  2. As the previous but referring to wood of a particular species.
    Teak is much used for outdoor benches, but a number of other woods are also suitable, such as ipé, redwood, etc.
  3. A forested or wooded area, most often used in the plural.
    He got lost in the woods beyond Seattle.
  4. Firewood.
  5. A type of golf club, the head of which is frequently made of wood.
  6. A woodwind instrument.
  7. An erection.
substance
wood from a particular species
  • Finnish: puulaji
  • German: Holz
woodland
  • Finnish: metsä
  • French: bois
  • Galician: fraga
  • German: Waldland, Waldung
  • Greek: δάσος
  • Korean: (sup), 수풀 (supul)
  • Norwegian: skog
  • Occitan: bòsc
  • Spanish: bosque
  • Swedish: skog
firewood
type of golf club
  • Finnish: puu, puumaila
  • German: Holz
music: woodwind instrument
  • Finnish: puupuhallin
slang: an erection
  • Finnish: stondis
  • German: Latte

Adjective

  1. Made of wood.

Synonyms

Translations

made of wood

Verb

  1. To cover or plant with trees.

Translations

to cover or plant with trees

Etymology 2

Old English wōd.

Adjective

en-adj er
Wood is hard, fibrous, lignified structural tissue produced as secondary xylem in the stems of woody plants, notably trees but also shrubs. It conducts water to the leaves and other growing tissues and acts as a support function, enabling plants to reach large sizes. Wood may also refer to other plant materials and tissues with comparable properties.
Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It is composed of fibers of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).
Wood has been used for millennia for many purposes. One of its primary uses is as fuel. It is also used as for making artworks, furniture, tools and weapons, and as a construction material.
Wood has been an important construction material since humans began building shelters, houses and boats. Nearly all boats were made out of wood till the late 1800s, and wood remains in common use today in boat construction. New domestic housing in many parts of the world today is commonly made from timber-framed construction. 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 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.
Wood unsuitable for construction in its native form may be broken down mechanically (into fibres or chips) or chemically (into cellulose) and used as a raw material for other building materials such as chipboard, engineered wood, hardboard, medium-density fiberboard (MDF), oriented strand board (OSB). 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.
Wood is also used for cutlery, such as chopsticks, toothpicks, and other utensils, like the wooden spoon.

Formation

A tree increases in diameter by the formation, between the old wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. Where there are clear seasons, this can happen in a discrete pattern, leading to what is known as growth rings, as can be seen on the end of a log. If these seasons are annual these growth rings are annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.
Within a growth ring it may be possible to see two parts. The part nearest the center of the tree is more open textured and almost invariably lighter in colour than that near the outer portion of the ring. The inner portion is formed early in the season, when growth is comparatively rapid; it is known as early wood or spring wood. The outer portion is the late wood or summer wood, being produced in the summer. In white pines there is not much contrast in 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 late wood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored early wood. In ring-porous woods each season's growth is always well defined, because the large pores of the spring abut on the denser tissue of the fall before. 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.

Knots

A knot is a particular type of imperfection in a piece of timber, which reduces its strength, but which may be exploited for artistic effect. In a longitudinally-sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the roughly parallel fibres (grain) of the rest of the "flows" (parts and rejoins).
A knot is actually a portion of a side branch (or a dormant bud) included in the wood of the stem or larger branch. The included portion is irregularly conical in shape (hence the roughly circular cross-section) with the tip at the point in stem diameter at which the plant's cambium was located when the branch formed as a bud. Within a knot, the fibre direction (grain) is up to 90 degrees different from the fibres of the stem, thus producing local cross grain.
During the development of a tree, the lower limbs often die, but may persist 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.
Knots materially affect cracking (known in the industry as checking) 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, direction of fiber, 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.
Knots do not necessarily influence the stiffness of structural timber. Only defects of the most serious character affect the elastic limit of beams. Stiffness and elastic strength are more dependent upon the quality of the wood fiber than upon defects in the beam. The effect of knots is to reduce the difference between the fiber stress at elastic limit and the modulus of rupture of beams. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.
For purposes for which appearance is more important than strength, such as wall panelling, knots are considered a benefit, as they add visual texture to the wood, giving it a more interesting appearance.
The traditional style of playing the Basque xylophon txalaparta involves hitting the right knots to obtain different tones.

Heartwood and sapwood

Heartwood is wood that has died and become resistant to decay as a result of genetically programmed processes. It appears in a cross-section as a discolored circle, following annual rings in shape. Heartwood is usually much darker than living wood, and forms with age. Many woody plants do not form heartwood, but other processes, such as decay, can discolor wood in similar ways, leading to confusion. Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once (Shigo 1986, 54).
Sapwood is living wood in the growing tree. All wood in a tree is first formed as sapwood. 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 food prepared in the leaves. 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 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 trees as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule.
There is no definite relation 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 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 sapwood, because of its position in the tree, may have certain advantages over heartwood.
It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds of years, 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.
There may be decided differences in the grain of heartwood and sapwood cut from a large tree, particularly one that is 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 species, the reverse applies. 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.

Different woods

There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. For every tree species there is a range of density for the wood it yields. There is a rough correlation between density of a wood and its strength (mechanical properties). For example, while mahogany is a medium-dense hardwood which is excellent for fine furniture crafting, balsa is light, making it useful for model building. The densest wood may be black ironwood.
Wood is commonly classified as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from 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 most hardwoods.
Wood products such as plywood are typically classified as engineered wood and not considered raw wood.

Colour

In species which show a distinct difference between heartwood and sapwood the natural colour of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous. This is produced by deposits in the heartwood of various materials resulting from the process of growth, increased possibly by oxidation and other chemical changes, which usually have little or no appreciable effect on the mechanical properties of the wood. Some experiments on very resinous Longleaf Pine specimens, however, indicate an increase in strength. This is 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.
Since the late wood of a growth ring is usually darker in colour than the early wood, 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 late wood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the colour of wood is no indication of strength.
Abnormal discolouration 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 discolouration 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 colours 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 fungous growth, but does not necessarily produce a weakening effect.

Structure

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 the hardwoods is more complex. They are more or less filled with vessels: in some cases (oak, chestnut, ash) quite large and distinct, in others (buckeye, poplar, willow) too small to be seen plainly without a small 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 localized 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 fibres. These fibres are the elements which give strength and toughness to wood, while the vessels are a source of weakness.
In diffuse-porous woods the pores are 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.
If a heavy piece of pine is compared with a light specimen it will be seen at once that the heavier one contains a larger proportion of late wood than the other, and is therefore considerably darker. The late wood of all species is denser than that formed early in the season, hence the greater the proportion of late wood the greater the density and strength. When examined under a microscope the cells of the late wood are seen to be very thick-walled and with very small cavities, while those formed first in the season have thin walls and large cavities. The strength is in the walls, not the cavities. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of early and late wood. The width of ring is not nearly so important as the proportion of the late wood in the ring.
It is not only the proportion of late wood, but also its quality, that counts. In specimens that show a very large proportion of late wood it may be noticeably more porous and weigh considerably less than the late wood in pieces that contain but little. One can judge comparative density, and therefore to some extent weight and strength, by visual inspection.
No satisfactory explanation can as yet be given for the real causes underlying the formation of early and late wood. 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. But in choosing a particular specimen it is not the width of ring, but the proportion and character of the late wood which should govern.
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 middle portion of the ring in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this middle portion 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 early wood occupy from 6 to 10 per cent of the volume of the log, while in inferior material they may make up 25 per cent or more. The late wood of good oak, except for radial grayish patches of small pores, is dark colored and firm, and consists of thick-walled fibers which form one-half or more of the wood. In inferior oak, such fiber areas are 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 the 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."
The effect of rate of growth on the qualities of chestnut wood is summarized 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."

References

  • Hoadley, R. Bruce. (2000) Understanding Wood: A Craftsman’s Guide to Wood Technology. Taunton Press. ISBN 1-56158-358-8
  • Shigo, Alex. (1986) A New Tree Biology Dictionary. Shigo and Trees, Associates. ISBN 0-943563-12-7
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