Glossary
Click a letter to jump to that section This glossary was derived from various sources and represents generally accepted usage of terms in the forest products industry. |
machine stress rated (MSR) Lumber that has been evaluated by means of nondestructive machine stress-rating equipment.
margo That portion of the membrane of bordered pits that supports the torus; that is, the membrane exclusive of the torus.
Master Wood Technology Program A high-achievement or top level wood technology program.
matched lumber Lumber that is edge-dressed and shaped to form a tongued and grooved or similar joint when pieces are laid side by side.
meniscus The curved upper surface of a liquid in a tube or container. Wood cells serve as containers for liquid water. The surface of the water in the cell is concave, owing to the effect of surface tension.
microfibril A threadlike component of the cell wall structure composed of chain molecules of cellulose extending through regions of parallel order known as crystallites and through regions of disorder known as amorphous regions. Microfibrils are the smallest natural units of cell wall structure that can be distinguished with an electron microscope.
middle lamella The lignin-rich layer that cements adjoining cells together. This layer is dissolved in the chemical pulping processes which separate wood into pulp fibers.
mildew Surface growths of fungi, usually dark gray in color, growing on the exterior wood of buildings.
millwork Planed and patterned lumber for finish work in building, including items such as sashes, doors, cornices, panel work, and other items of interior or exterior trim. Does not include flooring, ceilings, or siding.
millwright A person who design, builds, or sets up mills or machinery for mills.
mineral stain See stain.
modulus of elasticity A measure of the stiffness of wood.
modulus of rigidity A measure of the torsional 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 a percentage of the weight of the oven-dry wood.
mold Superficial, usually colored growth of fungi on damp wood; also referred to as mildew.
mortised A hole in one piece of wood cut to receive the projection on another piece.
moulder A machine that shapes into finished dimensions the face and edged surfaces.
MSF Abbreviation for "thousand square feet".
MSR Abbreviation for "Mechanically Stress Rated" as in lumber.
multi-torch A group of torches or nozzles that can be used at one time.
naval stores Oils, resins, tars, and pitch extracted from pine and fir trees. Historically, the term was derived to describe those products when they were used in the construction of wooden sailing vessels.
nose bar A beveled bar mounted parallel with the tip of the lathe knife and designed to compress the veneer block into the cutting edge of the lathe knife.
oleoresin A solution of resin in an essential oil that occurs in or exudes from many plants, especially softwoods.
open grain Common classification for woods with large pores, such as oak, ash, and walnut.
optimizing Making the most of or the most efficient. i.e. optimizing saw.
oven dry A term applied to wood dried to constant weight in an oven maintained at temperatures of from 214 degrees to 221 degrees F.
overlay A thin layer of paper, plastic, film, metal foil, or other material bonded to one or both faces of panel products, or to lumber, to provide a protective or decorative face or a base for painting.
packaged-loaded kiln A trackless compartment kiln for drying packages of stickered lumber or other wood products. The dryer usually has large doors that can be opened so that the kiln charge can be placed in or removed from the dryer by forklift trucks. It is usually a forced-air circulation kiln with fans mounted overhead or at the side.
pallet A horizontal platform device used as a base for assembling, storing, handling, and transporting materials and products as a unit load.
palletized Storing and /or shipping items on a pallet.
parallel laminated veneers Used as a substitute for solid sawn timbers formerly made from old growth trees.
parametric linking A design method whereby the design details such as the geometry and the location of arcs and lines are linked to the outside dimensions of the part. This allows the design to be easily scaled to match the part dimensions when ever they are changed.
parenchyma Short cells having simple pits and functioning primarily in the metabolism and storage of plant food materials. They remain alive longer than the tracheids, fibers, and vessel segments, sometimes for many years. Two kinds of parenchyma cells are recognized: those in vertical strands, known more specifically as axial parenchyma, and those in horizontal series in the rays, known as ray parenchyma.
particleboard A generic term for a panel manufactured from lignocellulosic materials - commonly wood - essentially in the form of particles (as distinct from fibers). These materials are bonded together with synthetic resin or other suitable binder, under heat and pressure, by a process wherein the interparticle bonds are created wholly by the added binder.
phenolic resins Synthetic petrochemical-based adhesives used in the manufacture of hot-pressed plywood.
phloem Inner bark tissue, characterized by the presence of sieve tubes and serving for the transport of foodstuffs.
pile In air drying, stacking lumber layer by layer, separated by stickers or self stickering, on a supporting foundation (hand stacked). Also, stickered unit packages by lift truck or crane, one above the other on a foundation and separated by bolsters.
- Box pile - A method of flat stacking random length lumber for air drying or kiln drying. Full-length boards are placed in the outer edges of each layer and shorter boards in between are alternated lengthwise to produce square-end piles, unit packages, or kiln truckloads.
Machine-stacked pile - Unit packages of stickered lumber or other wood products stacked by mechanical means onto a pile foundation and one above another to build a pile of packages.
Random-length pile - Stacking lumber of various lengths in the same pile or package. The pile or package is usually square at one end with the long length at the other end unsupported by stickers.
Self-stickered pile - Stacking in which the stock is used as stickers to separate the layers. In crib stacking, the boards are in contact at the tree corners. In level or sloped stacking of softwood boards and dimension, stock is used for stickers and the pile width is the same as the length. Hardwood dimension stock and railroad ties are often self stickered.
piler A person who piles or stacks materials.
pin knot See knots.
pit A discontinuity in the secondary cell wall normally found in adjacent pairs of cells forming a pathway for liquid movement between neighboring cells. The two halves of a pit pair are normally separated by a membrane consisting of the middle lamella and adjacent primary cell walls. Sometimes the central portion of the membrane is thickened to form a torus.
pit aspiration The displacement of the torus of a bordered pit pair against one of the pit borders closing the pit aperture.
pit pair Two complementary pits of adjacent cells.
pitch pocket An opening extending parallel to the annual layers that contains, or has contained, either solid or liquid pitch.
pitch streaks A local accumulation of resin in the form of a streak, occurring in certain softwoods.
pith The small core of soft primary tissue occurring near the center of a tree stein, branch, and sometimes, root.
pith flecks Flecks on planed lumber caused by insects boring in the cambium layer, producing wound tissue with brownish contents.
plain sawn See fiat grain.
planer-matcher A surfacing machine for lumber. Profiler heads can be inserted to create side-matching pieces of wood - that is, tongue and groove or shiplap. See also matched lumber.
plank A piece of square-cut timber, generally more than 25 mm (1 in.) thick and 140 mm (6 in.) wide or greater, and of any length.
plenum chamber The space between the lumber stack and kiln wall for air circulation on the pressure side of a fan or blower in which the air is maintained under pressure.
platform frame system A framing system in which floor joists of the upper stories rest on the top plates of the story below (or on the foundation wall), and bearing walls and partitions rest on the subfloor of each story.
plenum chamber The space between the lumber stack and kiln wall for air circulation on the pressure side of a fan or blower in which the air is maintained under pressure.
plugs Sound wood of various shapes, used to replace defective portions of veneers. Also, synthetic plugs used to fill openings and provide a solid surface.
ply A single veneer lamina in a glued plywood panel.
plywood A composite panel or board made up of cross-banded layers of plies, bonded with an adhesive, of 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.
pneumatic relating to air, wind or gas.
pocket rot Advanced decay that appears in the form of a hole or pocket.
pores See vessels.
post and beam framing Construction in which posts and beams support the loads; the partition walls are not load-bearing. The roof is usually decking.
precision predryer A type of low temperature dryer. Stickered loads or unit packages of lumber or other wood products are placed in a large building provided with fans, heating system, and vents such that air of a given temperature and humidity can be circulated through the lumber.
preservative Any substance that, for a reasonable length of time, is effective in preventing the development and action of wood-rotting fungi, borers of various kinds, and harmful insects that deteriorate wood.
press drying A veneer drying method in which single green veneer sheets are placed between press platens under predetermined heat, pressure, and time; the resulting dry veneer is flat and uniformly dried to a desired moisture content.
pressure process Any process of treating wood in a closed container whereby the preservative or fire retardant is forced into the wood under pressures greater than 1 atmosphere (101 kPa). Pressure is generally preceded or followed by vacuum, as in the vacuum-pressure and empty-cell processes; or the applications of pressure and vacuum may alternate, as in the full-cell and alternating processes.
primer That coat of material that is applied directly over the uncoated surface.
program A high-achievement or top level wood technology program.
projected yield The amount of yield that is predicted and is usually based on research and statistical data.
psychrometer An instrument with both wet-bulb and dry-bulb thermometers for determining the amount of water vapor in the atmosphere.
pyrolysis Chemical decomposition of wood by the action of heat; that is, burning of wood.
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 center 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 a flat roof are sometimes called roof joists.
raised grain A roughened condition of the surface of dressed lumber in which the hard latewood is raised above the softer earlywood but not torn loose from it.
rate of recovery The rate at which something is recovered in a unit of time.
rat tailing A defect in a dried film caused by a bubble or a small piece of dirt, flowing downward on a vertical surface in such a way as to leave a thinner film of finishing material above it, due to the material having lost its flowing power, and somewhat resembling a rat tail.
rays, wood Ribbon like strands of tissue extending radially within a tree and varying in height from a few cells in some species to several centimeters 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.'
recorder-controller An instrument that continuously records dry- and wet-bulb temperatures of circulated air and regulators these temperatures in a dryer or kiln by activating automatic heat and steam spray valves.
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 a specified moisture content (green, air-dry, or oven-dry).
relative humidity Ratio of the amount of water vapor present in the air to the amount that the air would hold at saturation at the same temperature. It is usually considered on the basis of the weight of the vapor but, for accuracy, should be considered on the basis of vapor pressures.
relaxation Reduction of stress with time on a wood member maintained under constant deflection.
residuals Wood by-products of the primary peeling process; includes pulp chips, hog fuel, and peeler cores.
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 A comprehensive term for secretions of certain trees, or of insects feeding on them, that are oxidation or polymerization products of the terpenes, consisting of mixtures of aromatic acids and esters insoluble in water but soluble in ether, alcohol, and other organic solvents. These secretions often exude from wounds and are obtained commercially by tapping or by extraction with solvents. The term is also applied to synthetic organic products related to the natural resins.
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.
resistivity The resistance of a cubic centimetre of material, such as wood, to the direct-current flow of electricity between opposite faces.
ribbon stripe A form of figure produced on the surface of wood because of the presence of interlocked grain.
rift crack. See heart check.
rift sliced, rift sawn Also termed "comb-grain". Refers to method of producing veneer by slicing or sawing at an angle of approximately 45 degrees with the annual rings to bring out certain figures produced by the medullary rays, which are especially conspicuous in oak.
rigid frame A rib type of construction, formed from lumber joined at the crown and haunches by plywood gussets, that is easily fabricated and erected on site.
ring-porous Used in referring to a group of hardwoods in which the annual growth layers consist of a more or less continuous zone of 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. See also shake.
rip saw A saw that cuts along the lengthwise edge of lumber.
ripping Cutting lengthwise, parallel to the grain.
roller bar A rotating round bar mounted parallel with the tip of the lathe knife; designed to compress the veneer block into the cutting edge of the lathe knife.
rotary-cut veneer Veneer cut in a lathe that rotates a log or bolt against a knife set in such a manner as to peel off a continuous thin sheet. Also, a method of cutting veneers from a log. The log is steamed in a vat to soften the wood, the bark is removed and the whole log is mounted in a large lathe and turned against a long, sharp knife. As the log revolves the veneer is peeled off in long sheets. It also refers to manner of cutting veneer by which the entire log is centered in a lathe and turned against a broad cutting knife, which is set into the log at a slight angle.
rough lumber Lumber that has been sawn, edged, and trimmed but not dressed (planed).
sap Fluid contents of the living wood cells.
sap stain See stain.
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 color than heartwood and has lower natural resistance to decay.
sash A frame structure, normally glazed (e. g., a window), that is hung or fixed in a frame set in an opening.
sash gang saw A sash or frame holding a battery of parallel saws that move up and down on the end of a connecting rod attached to a heavy crank- shaft.
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.
sawyer A person whose work is sawing timber.
scaler A person who scales or measures the volume of timber or lumber.
scarf joint An end joint formed by joining with glue the ends of two pieces that have been tapered or beveled, usually to a feather edge, to form a slope of the same length and inclination in both pieces.
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.
sealers Undercoating materials for sealing a surface in preparation for painting, varnishing, or application of final finish.
seasoning. See drying.
second growth Trees that replace the original virgin stand of timber.
semichemical pulp Pulp obtained by mild treatment of wood chips by any of the chemical pulping processes, which remove only part of the Iignin from the wood chips, followed by mechanical treatment to complete the separation of individual cellulose fibers.
set A permanent or semipermanent deformation in wood caused by internal stresses.
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.
shakes In construction, a type of shingle usually hand cleft from a bolt and used for roofing or weatherboarding.
shear The displacement of woody tissues following fracture as a result of shearing stresses which cause the fibers to slide relative to one another.
shear, longitudinal Shearing stress that tends to cause the fibers to slide over each other lengthwise.
shear strength The capacity of a body to resist shearing stresses.
sheathing The structural covering, usually of boards, building fiberboards, waferboard, or plywood, placed over exterior studding or rafters of a structure.
shim stock Thin strips of wood used to level off irregularities under a hardwood floor.
shingles Thin, rectangular pieces of wood, sawn along the grain and tapering in thickness, used like tiles for roofing and weatherboarding.
shrinkage Contraction caused by drying wood below the fiber saturation point; it is greater in the wide face of flat-grain than in edge-grain lumber, and minimal in the longitudinal direction.
siding (cladding) The finish covering of the outside wall of a frame building, whether made of horizontal weatherboards, vertical boards with battens, shingles, or other material.
sinker A log which sinks in water.
sinker stock Green lumber or other green sawmill products that will not float in water. Sinker stock may be sawn from sinker logs that were water-logged during ponding or from freshly cut logs containing wetwood. The green moisture content is abnormally high, and the lumber tends to dry slowly and is prone to develop checks and honeycomb.
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.
soft rot A special type of decay developing under very wet conditions in the outer wood layers, caused by certain fungi that destroy the cellulose in the secondary cell walls; as a result the wood becomes soft. The decayed wood is similar in appearance to brown rot.
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.
sorter
Drop - A mechanical lumber-sorting device that sorts lumber for thickness, width, and length by dropping them into separate compartments accordingly.
Edge - A mechanical lumber-sorting device consisting of grooves or slots in which the lumber is placed on edge. Lines of live rolls, arranged under the slots, carry the lumber to the desired bin or compartment.Tray - A mechanical lumber-sorting device consisting of a series of trays one above the other into which the lumber is ejected by either mechanical or electrical signaling devices.
spalt The pie-shaped portion of a shingle bolt that remains after processing.
specific gravity See relative density.
specific heat The heat in joules required to raise the temperature of one gram of wood 1°c.
spike grid A type of wood connector with teeth projecting from both surfaces that cut into the wood members as they are drawn together.
spike knot See knots.
spiral grain Wood in which the fibers take a spiral course about the stem of a tree. The spiral may extend toward the right or left around the tree stem. Spiral grain is a form of cross grain.
splints Trim from the edges of shingles and shakes.
splits Separations along the grain extending through a piece. Commonly caused by stresses set up in the wood during drying.
sporophore The fruiting body of a fungus; a conk.
spray booth A booth or area where finishing sprays such as primers, sealers or other finishes are applied so as to contain the sprays.
spray line A plain pipe of varying sizes and lengths that is drilled with holes of various sizes and spacing through which steam is injected into the kiln.
springwood See earlywood.
square edge Free from wane and without eased edges.
stain A discoloration in wood that may be caused by such diverse agents as microorganisms, sunlight, metals, chemicals, and chemical interaction The term also applies to materials used to impart color to wood.
- blue stain A bluish or grayish discoloration of the sapwood caused by the growth of certain dark-colored fungi on the surface and in the interior of the wood. Blue stain is made possible by the same conditions that favor the growth of other fungi.
- brown stain A dark brown discoloration of the sapwood of some pine logs that occurs during storage. Sometimes called `coffee-brown stain,' it is caused by a fungus.
- chemical brown stain A brownish discoloration that may occur during the seasoning of certain softwoods, apparently caused by the concentration and oxidation of extractive chemicals.
- hemlock brown stain See chemical brown stain.
- mineral stain An olive to greenish-black or brown discoloration of undetermined cause in hardwoods.
- sap stain See blue stain.sawyer A person whose work is sawing timber.
scaler A person who scales or measure the volume of timber or lumber.
spray booth A booth or area where finishing sprays such as primers, sealers or other finishes are applied so as to contain the sprays.
stacker A person who stacks or piles materials.
sticker stain A brown or blue stain that develops on lumber during seasoning where the stickers contact the boards.
star shake A number of heart shakes more or less in the form of a star.
stem The principal axis of a tree, capable of producing sawlogs, veneer logs, large poles, or pulpwood.
stickers Narrow wood strips used to separate the layers of lumber in a pile and thus improve air circulation.
straight grain Wood in which the fibers are aligned parallel to the axis of the piece.
strandwood A board made of long, narrow slices of softwood (mostly poplar) bonded together in one direction in the horizontal plane, forming the middle layer, or core, in composite plywood.
strength The limit of ability of a member to sustain stress. Also, in a specific mode of test, the maximum stress sustained by a member loaded to failure.
strength ratio The hypothetical ratio of the strength of a structural member to that which it would have if it contained no strength-reducing characteristics (knots, cross grain, shake, etc.).
stress grades Lumber grades having assigned working stress and modules of elasticity values in accordance with accepted principles of strength grading.
stress, working See allowable unit stress.
structural timbers Pieces of wood of relatively large size, the strength of which is the controlling element in their selection and use. Examples are trestle timbers (caps, posts, sills, bracing, bridge ties, guardrails); car timbers (car framing, including upper framing; car sills); framing for building (posts, sills, girders); ship timber (ship timbers, ship decking); and cross-arms for poles. See also timbers.
stud One of a series of slender wood structural members used as supporting elements in walls and partitions.
stump figure Figure produced by irregular grain in wood from the stump or base of a tree.
subfloor Boards or panel products used over floor joists as a working platform. See also underlayment.
summerwood See latewood.
