Module 8: Wood Utilization and Technology

Glossary of Key Terms - Module 8

air dried: Dried by exposure to air in a yard or shed, without artificial heat.

annual layers (rings): The layers of wood grown by a tree during a single growing season; in the temperate zone, annual layers of many species are readily distinguished because of differences in the cells formed during the early and late parts of the season.

band saw: A band of steel with teeth on one edge (single cutting) or both edges (double cutting), running on a set of large wheels. Used for longitudinal cutting of wood.

bent wood: Curved wood formed by steaming or boiling, or by special finishing, and then bending to a form.

bird's-eye figure: Figure produced on flat-sawn or rotary-cut surfaces by small, conical depressions of the fibres, which form numerous rounded areas of the grain remotely resembling small eyes. Generally limited to hard maples.

bleaching, pulp: The process of removing residual lignin from pulp to improve the brightness and strength.

board: Lumber that is less than 38 mm (2 in.) thick and wider than 38 mm (2 in.).

bolt: A short section of wood, as cut for shingles, shakes, rough dimension stock, stakes, pallet and crating material, and rotary-cut veneer.

bound moisture: See bound water.

brash wood: Wood with low resistance to shock and with a tendency to sudden and complete breakage across the grain without splintering.

brown rot: A condition caused by fungi that decompose the cellulose and associated carbohydrates in wood rather than the lignin. The result is a brown, friable residue. Sometimes called 'brown cubical rot' because of the formation of cracks caused by shrinkage.

bucking: Cross-cutting felled trees into logs or bolts.

bull edger: A combination circular gang resaw and edger used to break down small cants as well as for edging.

cambium: A thin layer of tissue between the bark and wood that repeatedly subdivides to form new wood and bark cells.

cant: A log that has been slabbed on one or more sides by the headrig for subsequent breakdown into lumber by other machines.

cell: A general term for the structural units of plant tissue, including wood fibres, vessel members, and other elements of diverse structure and function.

cellulose: The carbohydrate that is the principal constituent of wood and forms the framework of the wood cells.

checks: Lengthwise separations of wood that usually extend across the annual layers and commonly result from stresses set up in wood during drying.

chipper canter: A headrig machine that reduces barked logs directly to chips and cants without producing sawdust.

chucked: Attached to chucks or dogs which hold the log in place.

circular saw: A circular metal plate with teeth on the circumference that rotates on a drive shaft.

collapse: The flattening of single cells or rows of cells in the heartwood during the drying or pressure treatment of wood. The wood surface is often characterized by a caved-in or corrugated appearance.

composites: Built-up, bonded products consisting wholly of natural wood, or in combination with metals, plastics, etc.

compression wood: Abnormal wood formed on the lower side of branches and inclined stems of softwood trees. Compression wood is identified by its relatively wide annual layers and dark reddish colour. Compared with normal wood, it shrinks excessively lengthwise.

conditioning: The use of humidity in a dry kiln to produce a uniform distribution (equalization) of moisture in timber and to reduce drying stresses.

conk: the exterior fruiting body produced by an interior wood-rotting fungus.

cooperage: Containers, such as barrels and kegs, consisting of two round head pieces and body composed of staves held together with hoops.

cross grain: Wood in which the fibres are not aligned parallel to the axis of the piece.

cupping: Distortion of a board whereby the faces become concave or convex across the grain or width. This condition usually occurs in drying.

decay: The decomposition of wood substance by fungi. The destruction is readily recognized because the wood has become punky, soft and spongy, stringy, ring-shaked, pitted, or crumbly. Decided discoloration or bleaching of the rotted wood is often apparent.

deflection: Is a measure of the movement of a wood member in response to an applied load. Conversely, it is a measure of stiffness (see modulus of elasticity).

degrade: A reduction in the quality of wood due to defects that result from seasoning.

density: As usually applied to wood of normal cellular form, density is the mass of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex having unit volume. It is variously expressed as kilograms per cubic metre or pounds per cubic foot at a specified moisture content.

depression, wet-bulb: The difference between the dry-bulb and wet-bulb temperature.

diffuse-porous wood: Wood from certain hardwood species whose pores are nearly uniform in size and distributed evenly through the annual layer (e.g., birch and maple). Annual layers are sometimes difficult to identify

dimension lumber: Lumber with a thickness of 38 mm (2 in.) up to, but not including, 114 mm (5 in.) and a width of 38 mm (2 in.) or more.

dogs: Steel, teeth-like projections usually attached to the knee of a headrig carriage to hold the log firmly in position on the carriage headblock.

dressed lumber: Lumber surfaced on one or more sides by a planer.

dry-bulb temperature: The temperature of air as indicated by a standard thermometer.

dry (seasoning): Removing moisture from green wood to improve its serviceability and utility.

earlywood: The portion of the annual layer that is formed during the early part of the growing season (also called springwood). It is usually less dense and weaker mechanically than latewood.

edge grain: Lumber in which the annual layers form an angle of 45-90° with the wide surface of the piece. Also referred to as 'quarter sawn' or 'vertical grain'.

edger: A machine used to produce two parallel sides (wide face) by removing the rounded edges of a board (wane). Lumber is edged to specified width (softwoods) and to random width (hardwoods).

encased knot: A knot whose annual layers are not intergrown (i.e., not continous) with those of the surrounding wood.

fiberboard: A broad, generic term inclusive of sheet materials of widely varying densities manufactured of refined or partially refined wood (or other vegetable) fibres. Bonding agents and other materials may be added to increase strength or resistance to moisture, fire, or decay.

fibre saturation point: The stage in the drying or wetting of wood at which the cell walls are saturated and the cell cavities are free from water. It is usually taken as approximately 2530% moisture content, based on ovendry weight.

fibre, wood: Long, thin, cylindrical wood cells, tapered and closed at both ends. Also a general term of convenience for any long, narrow cellular tissue.

fiddleback figure: Figure produced by type of fine wavy grain wood. Wood with such figure is traditionally used for the backs of violins.

figure: Any characteristic pattern produced in a wood surface by annual growth rings, rays, knots, deviations from regular grain such as interlocked and wavy grain, and irregular coloration.

fine grain: A non-technical term variously used to describe wood with narrow, inconspicuous annual layers or with relatively small or uniform cell diameters.

finger joint: An end joint made up of several meshing fingers of wood bonded together with adhesive.

flat grain: The figure produced when lumber is sawn approximately tangent to the annual layers. Lumber is considered flat-grained when the annual layers make an angle of less that 45° with the surface of the piece.

flat sawn: Another term for flat grain.

flitch: A portion of a log sawn on two or more sides, frequently with wane on one or both edges, and intended for further conversion into lumber.

framing: Dimension lumber used for the structural members of building, such as studs, joists, and rafters. Light and Structural Light Framing are grades of lumber 38-89 mm (2-4 in.) thick and 38-89 mm (2-4 in.) wide.

free water: Moisture that is contained in cell cavities and intercellular spaces and is held by capillary forces only.

fungi: A low form of chlorophyll-less non-vascular plant life. Wood-inhibiting fungi use constituents of wood as food and also require moisture, oxygen, and suitable temperatures in order to develop.

grain: In its restrictive meaning, grain designates the direction of alignment of wood elements that determines a plane of cleavage. This term is also used in a variety of ways to describe the size, arrangement, appearance, or other qualities of wood fibres.

green: Used in referring to freshly sawn or undried wood. Wood that has become completely wet after immersion in water is not considered green but my be said to be in the 'green condition'.

hardwoods: Generally one of the botanical groups of trees that have broad leaves in contrast to the conifers or softwoods. The wood produced by these trees contains pores. The term has no reference to the actual hardness of the wood.

headrig: The first machine in a sawmill to start the breakdown of logs into lumber products.

headsaw: The principal saw in a sawmill used for the breakdown of logs by cutting parallel to the grain.

heart check: A radial shake originating from the heart or central portion of a log. Also called 'heart shake' and 'rift crack'.

heartwood: The inner core of a woody stem, where the cells no longer participate in the life processes of the tree. Usually contains extractive materials that give it a darker colour and greater decay resistance than the outer enveloping layer (sapwood).

hogged wood: Pieces of solid wood that have been reduced to particles by a grinder (hog) or crusher, prior to burning or pelletizing.

honeycombing: A term used to describe advanced white rot; also checks, that occur in the interior of a piece of wood, usually along the wood rays during seasoning.

joist: One of a series of parallel beams used to support floor and ceiling loads and supported in turn by larger beams, girders, or bearing walls.

kerf: The narrow slot cut by a saw as it advances through wood, or the thickness of wood removed as sawdust by a saw.

kiln: A chamber having controlled air flow, temperature, and relative humidity used for drying lumber, veneer, and other wood products.

-compartment kiln: A dry kiln in which the total charge of lumber is dried as a single unit.

- progressive kiln: A dry kiln in which the total charge of lumber is dried as several units, such as kiln truck loads, that are moved progressively through the kiln. The temperature is lower and the relative humidity is higher at the end where the lumber enters the kiln than at the discharge end.

kiln dried: Wood dried in a kiln to not more than 19% moisture content.

kiln schedule: A prescribed series of dry-bulb and wet-bulb temperatures and air velocities used in drying a kiln charge of lumber or other wood products.

knots: Those portions of a branch or limb that have been surrounded by subsequent growth of the stem. The shape of a knot as it appears on a cut surface depends on the plane of the cut relative to the long axis of the knot.

- encased knot: A knot whose annual layers are not intergrown (i.e., not continuous) with those of the surrounding wood.

- intergrown knot: A knot whose annual layers are intergrown (i.e., continuous) with those of the surrounding wood.

- loose knot: A knot that is not held firmly in place or position and that cannot be relied upon to remain in place.

- spike knot: A knot sawn approximately parallel to its long axis so that the exposed section is definitely elongated.

kraft (sulphate) process: A chemical pulping process in which lignin is dissolved by a solution of sodium hydroxide and sodium sulphide.

kraft pulp: A chemical wood pulp obtained by cooking wood chips at high temperature in a solution of sodium hydroxide and sodium sulphide.

laminated veneer lumber (LVL):
Lumber cut from large laminated wood panels, of various thickness. Grain of all laminates runs in same lengthwise direction.

laminated wood: An assembly made by bonding layers of veneer or lumber with an adhesive so that the grain of all laminations is essentially parallel.

latewood: The portion of the annual layer that is formed during the latter part of the growing season after the earlywood formation has ceased (also called summerwood).

linerboard: A paperboard used as a facing material in corrugated and solid fibre shipping containers. Linerboard is usually classified according to furnish, as for example, kraft linerboard.

live sawing: Sawing through and through without turning the log or by turning it only once - that is, sawing with a bandmill headrig or with a circular headrig.

longitudinal: Generally, parallel to the direction of the wood fibres.

lumber: The product of saw and planing mills that is not further manufactured beyond sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching.

mechanical pulping: The production of fibres and fibre bundles by grinding wood with pulpstones or by mechanical refiners as opposed to chemical methods.

modulus of elasticity: A measure of the stiffness of wood.

modulus of rupture: A measure of the maximum strength of wood.

moisture content: The amount of water contained in wood, usually expressed as percentage of the weight of the oven-dry wood.

mold: Superficial, usually coloured growth of fungi on damp wood; also referred to as mildew.

open grain: Common classification for woods with large pores, such as oak, ash, and walnut.

oriented strand-board (OSB): An engineered panel product using wafer or strands of wood oriented in specific configurations to achieve a desired strength characteristic.

pallet: A horizontal platform device used as a base for assembling, storing, handling, and transporting materials and products as a unit load.

particleboard: A generic term for a panel manufactured from lignocellulosic material - common wood - essentially in the form of particles (as distinct from fibres). These materials re bonded together with synthetic resin or other suitable binder, under heat and pressure, by process wherein the interparticle bonds are created wholly by the added binder.

pit: A discontinuity in the secondary cell wall normally found in adjacent pairs of cells forming pathway for liquid movement between neighbouring cells.

pith: The small core of soft primary tissue occurring near the centre of a tree stem, branch, and sometimes, root.

plywood: A composite panel or board made up of cross-banded layers of plies, bonded with an adhesive, or veneer only, or veneer in combination with a core of lumber, or of particleboard. Generally the grain of one or more plies is roughly at right angles to that of the other plies, and almost always an odd number of plies are used.

radial : Coincident with a radius from the axis of the tree or log to the circumference. A radial section is a lengthwise section in a plane that passes through the centre line of the tree stem.

rafter: One of a series of parallel structural members of a roof designed to support roof loads. The rafters of flat roof are sometimes called roof joists.

rays, wood: Ribbon-like strands of tissue extending radially within a tree and varying in height from few cells in some species to several centimetres in oak. The rays serve primarily to store food and transport it horizontally through the tree.

reaction wood: Wood with abnormal structure and properties formed in parts of leaning or crooked stems and in branches. In hardwoods it is called 'tension wood'; in softwoods, 'compression wood'.

relative density: Formerly called specific gravity. As applied to wood, the ratio of the oven-dry weight of a sample to the weight of a volume of water equal to the volume of the sample at specified moisture content (green, air-dry, or oven-dry).

resaw: A sawing machine used to break down cants into lumber, for recovering lumber from slabs, and for upgrading lumber by ripping off defective portions.

resin ducts: Intercellular canals or passages that contain and transmit resinous materials. They may extend vertically parallel to the axis of the tree or at right angles to the axis and parallel to the rays.

ring-porous: Used in referring to a group of hardwoods in which the annual growth layers consist of a more or less continuous zone or large earlywood pores that changes relatively abruptly to a denser latewood zone having smaller pores and an abundance of fibrous tissue (e.g., oak and ash).

ring shake: A separation along the grain that occurs most commonly between adjoining annual layers.

rotary-cut veneer: Veneer cut in a lathe that rotates a log or bolt gainst a knife set in such a manner as to peel off a continuous thin sheet.

rough lumber: Lumber that has been sawn, edged, and trimmed but not dressed (planed).

rupture: Means the point at which wood fails in response to an applied load (see also modulus of rupture).

sap: Fluid contents of the living wood cells.

sapwood: The wood located near the outside of the tree stem containing the tissues actively involved in the transport of sap. It is generally lighter in colour than heartwood and has lower natural resistance to decay. sawing around: Breaking down a log by turning it on the carriage of a headsaw to obtain the best yield of lumber from the clear outer portion of the log.

sawn veneer: Veneer produced by sawing.

scrag saw: Two or more pairs of saws, one pair to a drive shaft, or two or more pairs of saws, each saw on an individual drive shaft, all sawing different lines. Saws may be fixed or adjustable to different settings.

setworks: The mechanism on an edger, on a log carriage, or on twin and quad bandsaws for regulating the thickness of the wood being cut.

shake: A rupture or separation along the grain. The term is most commonly applied to 'ring shakes', which develop tangentially either within a given annual layer or at the boundary between two layers.

shrinkage: Contraction caused by drying wood below the fibre saturation point; it is greater in the wide face of flat-grain than in edge-grain lumber, and minimal in the longitudinal direction.

slab: The exterior portion of a log removed in sawing lumber.

sliced veneer: Veneer that is sliced off a log, bolt, or flitch with a knife.

softwoods: Generally, one of the botanical groups of trees that in most cases have needlelike or scalelike leaves (the conifers); also the wood produced by such trees. The wood does not contain pores. The term has no reference to the actual hardness of the wood.

splits: Separations along the grain extending through piece. Commonly caused by stresses set up in the wood during drying.

springwood: See earlywood

straight grain: Wood in which the fibres are aligned parallel to the axis of the piece.

stud: One of a series of slender wood structural members used as supporting elements in walls and partitions.

summerwood: See latewood

tangential: Strictly, coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent. In practice, however, it often means roughly coincident with an annual layer. A tangential section is a longitudinal section through a tree or limb perpendicular to a radius. Flat grain lumber is sawn tangentially.

tension wood: Reaction wood formed on the upper side of branches and inclined stems of hardwood trees. Tension wood is characterized anatomically by lack of cell-wall lignification and often by the presence of gelatinous fibres. It has excessive longitudinal shrinkage, and sawn surfaces usually have projecting fibres. Planed surfaces often are torn or have raised grain.

texture: Refers to the size of the cellular components of wood; may also describe their relative uniformity in size.

thermo-mechanical pulp: Is a newsprint pulping process whereby wood chips are first subjected to extremely high heat in a water medium; then refined through a disc-refiner to separate fibres from lignin. Basically, replaces the mechanical ground wood system.

trimmer: A battery of adjustable saws for trimming lumber to specific lengths or for removing defects.

twin and quad bandsaws: A twin bandsaw is an adjustable, double bandsaw headrig making two cuts simultaneously. A quad bandsaw makes four cuts simultaneously.

veneer: A thin layer or sheet of wood.

vessels: Tube-like structures in porous woods (hardwoods only) made up of longitudinal series of relatively short, large-diameter cells having more or less open ends. Open vessels exposed on the surfaces of a piece of wood are known as pores.

waferboard: A type of particleboard composed of wafers cut from roundwood bolts (mostly poplar) of uniform length and thickness resembling small pieces of veneer. The wafers re bonded together with resin binder, under heat and pressure, by a process similar to that by which particleboard is made.

wane: Bark or lack of wood from any cause on any edge or corner of a piece of lumber.

wet-bulb temperature: The temperature when the thermometer bulb is kept moistened and hence cooled by evaporation. Because evaporation is greater in dry air, the thermometer will register a lower temperature at lower relative humidity.

white rot: A condition caused by fungi attacking the cellulose and lignin of wood simultaneously, resulting in whitish residue that may be spongy or stringy. May occur as pocket rot.