Woodworking Glossary



Return to glossary index

The capillary of cellular attraction of adherent surfaces to draw off the liquid adhesive film into the substrate

Acrylic Resins:
Resins made by the polymerization of acrylic monomers, such as ethyl acryl ate and methyl methacrylates (used in 2nd generation.

The substance or surfaces to which the adhesive is applied; the surfaces which are bonded together.

Adhesion Failure:
Failure of an adhesive, sealant or coating by pulling away from the surface with which it is in contact.

A substance capable of holding materials together by surface attachment.

Adhesive, Intermediate Temperature Cure:
Adhesive capable of curing at temperatures between 87F and 211F.

Adhesive, Pressure Sensitive:
An adhesive made so as to adhere to a surface at room temperature by briefly applied pressure alone.

Adhesive, Room Temperature Curing:
Adhesive capable of curing at temperature between 68F and 86F.

Adhesive, Separate Application:
A two-part adhesive which is used by applying one part to one adherent and one part to the other and bringing them together to form a bond.

Adhesive Solvent:
An adhesive having a volatile organic solvent as a fluid carrier.

Adhesive Spread:
The amount of adhesive applied to an adherent in terms of grams of liquid or solid adhesive per square meter or pounds per square feet of joint area. Application to one adherent surface is called "single spread". Double glue line refers to an adhesive spread applied to opposite faces of the same sheet of veneer. "Double spread", often referenced in timber laminating, refers to adhesive application- to both adherents.

Adhesive, Structural:
A material employed to form high strength bonds in structural assemblies may be used in extreme service conditions, e.g., high and low temperature exposures.

Adhesive, Synthetic Resin:
A synthetic resin product, not limited to, but including, amino-plast (urea and melamine formaldehyde resins), resorcinol and phenolic resins.

Adhesive, Two Component:
An adhesive supplied in two parts which are mixed before application.

The attraction between adhesive and adherent.

Albumin, Blood:

Organic compound whose molecules do not have their carbon atoms arranged in a ring structure.

Alkyd Resins:
Resins composed principally of polymeric esters, (polyesters) in which the recurring ester groups are an integral part of the main polymer chain, and in which ester groups occur in most cross links that may be present between chains.

(Cratering) A term used to describe the defect in an applied coating or mastic when it cracks into large segments. When the action is fine and incomplete it is usually referred to as "checking".

Ambient Temperature:
Temperature of the surrounding air.

Pertaining to or nature of starch.

Animal Glue:

Annual Growth Ring:
The growth layer put on by a tree during a single year, including summerwood and springwood.

Application Temperature Limits:
Temperature between which it is usually safe to apply finishes, adhesives and sealants.

A device used to spread an adhesive as a film of the desired thickness.

Water based or containing water.

Organic compound whose molecules have the carbon atoms arranged in a ring structure.

A dark brown to black cementitious material, solid or semisolid in consistency, in which the predominating constituents are bitumens which occur in nature as such or are obtained as residue in refining petroleum. The principal ingredient in asphalt is a mastic.

Asphalt Emulsion:
A colloidal (dispersing agent) dispersion of petroleum asphalt in water. The emulsifying agent may be a colloidal clay or a chemical soap.

The collection of and placing together in proper order of the layers of veneer, lumber and/or other materials, with the adhesive, ready to be pressed and bonded into a product.

Assembly Time, Closed:
The time from closed contact of an assembly having adhesive until application or full pressure.

Assembly Time, Open:
Time from spreading adhesive to the first surface until mating surfaces are in contact.

Assembly Time, Total:
The total of open and closed assembly times, which is the time from spreading glue to the first surface to the application of full pressure.

An early stage in the curing of thermosetting resin when the material is still fusible and soluble in certain solvents.

The reduction of a liquid to a fine spray by means of high pressure air or, as in airless spray, by pressure alone.

A heavy cylindrical vessel equipped for vacuum and/or pressure application. May have attachment for water supply and application of heat.


Return to glossary index

Usually the rear of unexposed surface of a plywood sheet that requires normal strength, but does not demand any selection for appearance. Should be reasonably equivalent to the face in thickness and strength.

A material placed into a joint, primarily to control the depth of the sealant.

The flexible supporting material for an adhesive, e.g., pressure sensitive adhesives are commonly backed with paper, plastic films, or fabrics.

An additive used to destroy bacteria occurring in adhesive formulations and to prevent their attack on the adhesive.

Bag Molding:
A molding or bonding process involving the application of pressure by means of air, water, stream, or vacuum, to a flexible cover (bag) which completely encloses the material being bonded.

Bale (Bundle):
A bundle or package of freshly glued wood assemblies. May or may not be held together by clamp irons in the event the adhesive curing is accomplished at room temperature. In the latter instance, the bale is kept under pressure until after initial adhesion is accomplished.

Bark Pocket:
An opening between annual growth layers that contains bark.

A sealant or compound after application in a joint irrespective of the method of application, such as caulking bead, glazing bead, etc. Also a molding or stop used to hold glass or panels in position.

The component of an adhesive which is mainly responsible for adhesive properties.

The penetration or dissolution of an adherent surface by an adhesive.

Hydrocarbon material of natural or pyrogenous origin, or combinations of both, which may be liquid, semisolid, or solid, and which is completely soluble in carbon disulfide.

Bleed Through:
Glue or components of glue that have seeped through the outer layer or ply of a glued wood product and that shows as a blemish or discoloration on the surface.

Anything marring the appearance of the veneer that is not classifiable as a defect.

Blister (Blow):
A spot or area where the veneer does not adhere and bulges like a blister. It may be caused by lack of glue or adhesive or inadequate pressure. In hot pressing, it may be caused by a pocket of stream which often ruptures the veneer.

Block (Bolt):
A short log cut to a length suitable for peeling on a lathe.

Blocking, n. :
An undesired adhesion between touching layers of material with or without adhesive.

Blood Glue:

Formation of condensation on the surface of a contact adhesive as the solvent evaporates and its temperature is rapidly lowered.

Adjective applied to stiff inflexible mastic or coating resembling a board.

To increase in consistency.

Boil Test:
Plywood shear test specimens are immersed in boiling water in conformance with the pro- procedure stated in many standards and specifically in PS 1-66 and PS 51-71 before being broken in a shear test machine.

A short log cut to length suitable for peeling on a lathe.

Bond, n.:
The attachment of an interface between an adhesive and an adherent.

Bond, v:
To attach materials together by means of an adhesive.

Bond Age:
Time period elapsed after bonding specimens prior to testing.

Bond Breaker:
Septum used where it is desired that the sealant not adhere.

Bond Strength:
The unit load applied in tension, compression, flexure, peel, impact, cleavage, or shear, required to break an adhesive assembly with failure occurring in or near the plane of the bond. See BOND.

Bonding Time Range:
Time period after application of adhesive, during which the adherents may be combined.

The distortion in a panel or board that deviates from flatness length-wise but not across its faces.

An internal void or a trapped globule of air or other gas which occurs during a mastic application. Different from a blister, which occurs after application.

Intermediate phase in the reaction of thermosetting mixtures during which the material gels and is not completely fused.

Bulk Density:
A measurement of powdered or granular materials in terms of the weight of a unit volume such as pounds per cubic foot.


Return to glossary index

"C" Factor: See Thermal Conductance


Cast Film:
A film made by depositing a layer of a coating or adhesive onto a surface, stabilizing this form, and removing the film from the surface.

A hardener for resin adhesives. A reagent that accelerates a chemical reaction, with or without heat. In the case of resinous adhesives, it accelerates setting or hardening. Usually does not take part in the reaction.

Boards, panels, or metal sheets that are used in gluing operations to provide uniform distribution of the gluing pressure; or used to prevent precure of glue by slowing up transfer of heat to plywood having thin face veneers.

Synonymous with adhesive.

Inner plies of a multi-layered product whose grain direction runs parallel to that of the outer ply.

One hundredth of a poise; unit of viscosity measure.

The act of certifying or attesting; a guarantee that a material meets certain specifications and so indicated by a stamp of the testing agency.

A lengthwise separation of the wood which usually extends across the annual growth rings, commonly resulting from the stresses setup in wood during seasoning.

Clamp Irons:
The pressure-maintenance equipment, which includes the I beam or double channel irons, together with right and left clamp screws or turnbuckle rods, to hold bales under pressure after cold gluing.

The shearing machine used to dimension green or dry veneers.

Initial state of film formation in a water base system.

The formation of emergent threads of adhesive during the operation of a spray gun applicator.

Coefficient of Expansion:
The ratio of the increase in length of a body for each degree rise in tempera- as compared to the original length of the body. May also apply to increase of area or volume.

The state in which the particles of a single substance are held together by primary or secondary valence forces. As used in the adhesive field, the state in which the particles of the adhesive (or the ad- adherent) are held together.

The protein derived from bone and skin used to prepare animal glue and gelatin.

Cold Flow:
The deformation of a material at room temperature without applied load.

Cold Pressing:
A bonding operation in which an assembly is subjected to pressure without the application of heat.

Cold Soak Test:
Glued wood test specimens are submerged in water at room temperature and then dried in conformance with the procedure stated in a testing method before being graded or broken in a shear test machine.

A state of suspension and dispersion of submicron particles in a liquid medium without their dissolution in the medium.

Commercial Standard (May have been superseded by Products Standards, described as Voluntary Standards):
A written trade standard developed by manufacturers, distributors, and users of an item in cooperation with the Commodity Standards Division of the Office of Technical Services, Business and Defense Services Administration (of the Federal Government), and with the National Bureau of Standards (a Federal Agency). Its purpose is to establish quality criteria, standard methods of test, rating, certification- and labeling of manufactured commodities, and to provide uniform bases for fair competition.

Compression Wood:
Abnormal wood formed on the lower side of branches and inclined trunks of softwood- wood trees. Compression wood is identified by its relatively wide annual rings, unusually eccentric, re- relatively large amount of summerwood, sometimes more than 50 percent of the annual rings in which it occurs, and its lack of demarcation between springwood and summerwood in the same annual rings. Compression wood shrinks excessively lengthwise as compared in normal wood.

Condensation, n.:
A chemical reaction in which two or more molecules combine with the separation of water or some other simple substance. If a polymer is formed, the process is called poly condensation.. See also POLYMERIZATION.

Conditioning Period:
That period of time required after removal of an adhesive bonded product from pressure to develop full strength.

Arrangement of veneers or lumber in the fabrication of plywood.

  All veneer construction
  Plywood in which all plies are of veneer. Ordinarily no single ply of veneer will exceed 1/4 inch in thickness. Balanced Construction - A construction such that the forces induced by uniformly distributed changes in moisture content will not cause warpage. Symmetrical constructions in which the grain directions of the plies are either parallel or perpendicular to each other are balanced constructions.

  Lumber Core Construction
  Plywood in which the center ply or core is of lumber rather than of veneer. Ordinarily cores that are 3/8 inch or greater in thickness will be of lumber.

  Symmetrical Construction
  Plywood panels in which the plies on one side of a center ply or core are essentially equal in thickness, grain direction, pro- properties, and arrangement to those on the other side of the core.

Continous Press:
Press made up of two pinch rolls that press material as it moves between the rolls.

A polymerization product of two or more different monomers.

(1): The center ply in a multi-layered wood product. It may be of lumber, particleboard, either one piece or several pieces, edge glued together or of one or more thicknesses of veneer. (2) In Plywood - Inner plies whose grain direction runs perpendicular to that of the outer plies. (3) In cutting rotary veneer, the portion of the bolt remaining after available veneer has been cut, also referred to as core blocks.

Core Gaps:
An opening or void extending into a panel, which occurs where the adjacent inner ply is separated at an edge joint.

The spreading power of an adhesive over the area of adherent.

Fine cracks that may extend in network within or beneath the surface of an adhesive layer; formation of fissures and voids in a film due to shrinkage or solvent action.

The dimensional change with time of a material under sustained load.

The transverse veneer layers that distinguish plywood from laminated wood. Their presence counteracts the tendency of wood to split as well as to shrink and swell. In standard 5-ply construction it is the layer between the face and the core, and between the back and the core, some- times called face crossing and back crossing respectively.

The union of adjacent molecules of uncured adhesives by catalytic or curing agents.

The final stage in the cure of certain thermosetting resins where the material becomes in- soluble and infusible.

Cup: A distortion of a panel or board in which there is a deviation flatwise from a straight line across the width of the panel or board.

To change the physical properties of a adhesive by chemical reaction, which may be condensation, polymerization or vulcanization; usually accomplished by the action of heat and catalyst, alone or in combination, with or without pressure.

Curing Agent:
Synonymous with accelerator, hardener, and catalyst.

Curtain Coater:
A liquid spreading machine which deposits a controlled thickness of coating liquid on a surface passing through it.

Any periodic repetition of a process.

Cycle Tests:
A method of exposing joints to alternating wet and dry conditions as a basis of determination waterproofness and durability.


Return to glossary index

Daylight (Dalite):
The clear vertical opening between the heated platens of a hot press, or between the head and base plates of a cold press.

The decomposition of wood by fungi.

Incipient Decay:
Early stage of decay that has not proceeded far enough to soften or otherwise perceptibly impair the hardness of the wood.

Advanced Decay:
The older stage of decay in which the destruction of the wood is readily recognized because the wood has become punky, soft and spongy, stringy or ringshaked. Discoloration or bleaching of the rotten wood is often apparent.

Any irregularity occurring in or on veneer that may lower its strength.

Defect, Open:
Any irregularly such as checks, splits, open joints, cracks, knot holes, or loose knots that interrupts the smooth continuity of the veneer.

The loss or removal of water from a substance.

Separation of plies; often used in reference to the durability of the glue line.

Increasing the density through compaction during pressing.

The weight of a body per unit volume. When expressed in the c.g.s. (center-gram-second) system, it is numerically equal to the specific gravity of the same substance.

Dielectric Curing:
The use of high frequency electric field through a joint to cure a thermosetting resin.

An ingredient usually added to an adhesive to reduce the concentration of bonding materials.

Dimensional Stability:
Characteristic of a material to retain its original dimensions when exposed to conditions conducive to cause a change, such as wood swelling when exposed to water.

The separation of individual fine particles in a liquid, gaseous, or solid medium.

Doctor Roll or Bar:
A device for regulating the amount of liquid glue on the rollers of the spreader.

Double Spread:

A kiln or chamber or machine through which the green or fresh veneer sheets are passed to remove the excess moisture.

Drying Time:
The period of time during which an adhesive or an adherent or an assembly is allowed to dry with or without the application of heat, pressure, or both.

The loss of moisture in a glue spread resulting in a poor bond.



Return to glossary index

Eccentric Pith:
The pith is said to be eccentric in a log when the center of growth (pith) and the geometric center of that log do not coincide.

A material which at room temperature can be stretched repeatedly to at least twice its original length and upon immediate release of the stress, will return to its approximate original length.

A suspension of fine particles of a liquid within another liquid which ordinarily do not dissolve- solve in each other.

End Splits:
Wedge-shaped openings in the ends of sheets of veneer caused by separation of the wood during drying, handling, or pressing.

Endothermic Reaction:
A chemical reaction that requires heat energy to initiate and sustain the reaction.

Equilibrium Moisture Content:
The moisture content at which lumber or other material suffers no loss or gain in moisture under the humidity and temperature conditions encountered.

Exothermic Reaction:
A chemical reaction evolving heat as a by-product of the process.

An additional substance, sometimes combined in resin adhesive, to reduce costs, and usually having supplementary adhesive characteristics, such as grain flours or soluble dried blood. The term filler in contrast, refers to relatively inert components added to the resin adhesives to control flow, provide body, or to impart some other desirable quality. Extenders are often used in high ratios, 100% or more of the resin content, while fillers seldom go beyond 25%. Increasing the extender ratio progressively reduces the durability. See FILLER.

Exterior Glue:
Usually a phenolic, resorcinol, or melamine resin which, when combined with suitable fillers, extenders, and other chemicals, will product glue bonds that will pass the appropriate standards for exterior use.

Exterior Plywood:
A term frequently applied to plywood, bonded with highly resistant adhesives, that is capable of withstanding prolonged exposure to severe service conditions without failure in the glue bonds.

Substances in wood, not an integral part of the cellular structure, that can be removed by solution in hot or cold water, ether, benzene, or other solvents that do not chemically react with wood components.

Adhesive applicator which extrudes liquid glue from orifices in the form of beads.



Return to glossary index

The better side of a panel in any grade calling for a face and a back; also, either side of a panel where the grading rules draw no distinction between faces. The quality of the face and back determines the grade of a panel within the exterior or interior type.

A condition of stress from repeated flexing or impact force upon the adhesive- adherent interface.

Fiber Tear:
The disruption of fibers during separation of paper, textiles, or wood.

A relatively non-adhesive substance added to an adhesive to improve its working properties, permanence, strength, or other qualities. See EXTENDER.

Film Forming:
The ability of an adhesive to form a stable continuous film.

A longitudinal section of a log or a bundle of matched veneers.

Movement of an adhesive during the bonding process, before the adhesive is set.

An ingredient used in the formulation of phenolic, urea, and melamine resins.

Freeze-Thaw Stable:
A system able to freeze and thaw without losing chemical or physical properties.



Return to glossary index

A semi-solid system consisting of a network of solid aggregates in which liquid is held.

Gel Point:
The stage at which a liquid begins to exhibit the properties of a gel.

Gel Time:
Time required for a liquid adhesive to form a gel under specified conditions.

The forming of a gel.

A term customarily applied to the older conventional cold setting adhesives, but now generally accepted as being synonymous with adhesive.

  Glue Types:

    is now used as a plywood adhesive, it usually is a special grade of dried blood. It is mixed cold and usually coagulated (set) under heat, but sometimes by chemical reagents. It is highly water-resistant. Blood is also used as an extender with other adhesives.

    Animal Glue
    is a derivative of bone and hide waste, usually prepared by cooking. Its application is best accomplished in a warm room with temperatures of glue solution at approximately 140F. It softens under moisture exposure, and eventually becomes resoluble.

    Casein Glue
    is dried milk product, mixed cold with lime, a sodium salt and other in- ingredients. Its action on edge tools is abrasive, and is weakened by soaking water.

    Liquid Glue
    is a prepared liquid adhesive or cement, usually sold at retail Many types have fish by-products as their base.

    Resin Adhesives
    See RESIN.

    Soy Flour
    is the residue of soybean after the oil has been removed. It is mixed cold with caustic, lime, and other substances. It can be applied on wet veneers, but is likely to stain delicately colored face veneers. It is a vegetable protein and, like casein, is partly re-soluble in water.

    Vegetable Glue
    is a starch product, usually with a cassava root flour base. It is prepared by cooking with caustic and cooled before use. It is sometimes used in the furniture and woodworking industry as it gives an excellent bond dry, but delaminates under moisture exposure.

Glue, v:
To attach materials together by means of glue. See BOND.

Glue Spread:
The amount of glue or adhesive spread in pounds of liquid mixture.

The designation of the quality of a manufactured piece of wood or of logs.

A stamp placed on a plywood panel which contains essential information about that panel. This information usually includes species, plywood grade and type of bond, and the certification by a commercial testing agency.

The direction, size, arrangement, appearance, or quality of the fibers in wood or veneer. To have a specific meaning, the term must be qualified.

  Close Grain
  produced by narrow and inconspicuous annual growth rings. The term is sometimes used to designate wood having small and closely spaced pores, but in this sense the term "fine textured" is more often used.

  Cross Grain
  a pattern in which the fibers and other longitudinal elements deviate from a line parallel to the sides of the piece. Applies to either diagonal or spiral grain or a com- combination of the two.

  Open Grain
  common classification for woods with large pores such as oak, ash, chestnut, and walnut. Also known as "coarse textured".

Grain Strength:
The strength of a joint on assembly with an unset adhesive.



Return to glossary index

A substance or mixture of substances added to an adhesive to promote or control the curing reaction by taking part in it. The term is also used to designate a substance added to control the degree of hardness of the cured film. See CATALYST.

Generally one of the botanical groups of trees referred to as deciduous which have broad leaves and lose them in the winter in contrast to conifers. The term has no reference to the actual hardness of the wood.

The wood extending from the pith to the sapwood, the cells of which no longer participate in the life of the tree. Heartwood may be infiltrated with gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.

High Frequency Heating:
Synonymous with dielectric curing.

Hot Melt:
A 100% solids adhesive requiring heat to raise the temperature of the adhesive to a workable viscosity.

Hot Pressing:
Manufacture of glued wood product under pressure and elevated temperature in a hot press,

Hot Stacking:
The stacking of plywood panels immediately after removal from the hot press, so that the residual heat in the panels may further cure the adhesive.

Humidity, Absolute:
Pounds of water vapor per pound of dry air.

Humidity, Relative:
Radio of amount of water vapor in air to the maximum amount of water vapor the air can hold at a given temperature.

The ability of materials to readily absorb and retain moisture from the atmosphere.



Return to glossary index

A material which retards a chemical reaction. Inhibitors are used to extend the shelf life and pot life of certain adhesives.

The contact area between adherent and adhesive surfaces.

Interior Glue:
Usually of vegetable or animal protein, starch, urea, or phenolic resin which, when combined with suitable fillers, extenders, and other chemicals, will produce glue bonds that have high dry strength, low to high wet strength, low to moderate durability under damp conditions, and low to high resistance to temperature in excess of 150F,

Interior Plywood:
A term frequently applied to plywood bonded with adhesives that maintain adequate bonds under conditions usually existing in the interior of buildings in the United States.



Return to glossary index

The junction of two adjacent pieces of wood or veneer.

  Butt Joint
  the place where two pieces of wood are joined together end to end.

  Edge Joint
  the place where two pieces of wood are joined together edge to edge.

  Glue Joint
  the place where two pieces of wood are joined together by means of glue.

  Open Joint
  failure of bond or separation of two adjacent pieces of veneer so as to have an opening, usually applied to edge joints between veneers.

  Starved Joint
  a glue joint which is poorly bonded because of an insufficient quantity of glue. Starved joints are caused by the use of short assembly time, excessive pressure, or insufficient viscosity of the glue, or a combination of these, which results in the glue being forced out from between the surfaces to be joined.

  Sunken Joint
  in the case of plywood, a depression in the surface of the face ply directly above an edge joint in the lumber core or cross band. Also may show directly in glue joint of edge glued panels having no face veneers. Usually the result of a shrinkage in the glue jointed layer.



Return to glossary index

The portion of a branch or limb which has been surrounded to subsequent growth of the wood of the trunk or other portion of the tree.

  Decay Knot
  a knot that, due to advanced decay, is softer than the surrounding wood.

  Encased Knot
  a knot whose rings of annual growth are not intergrown with those of the surrounding wood.

  Large Knot
  a knot more than 1-1/2 inches in diameter.

  Loose Knot
  a knot that is not held firmly in place by growth or position and that cannot be relied upon to remain in placed.

  Medium Knot
  a knot more than 3/4 inch but not more than 1-1/2 inches in diameter.

  Pin Knot
  a knot that is not more than 1/2 inch in diameter.

  Small Knot
  a knot more than 1/2 inch but not more than 3/4 inch in diameter.

  Sound Knot
  a knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.

  Knot by Cluster
  three or more knots in a compact, roughly circular group, with the grain between them highly contorted, originating from adventitious buds.

Voids produced by the dropping of knots from the wood in which they are originally embedded.



Return to glossary index

Two or more layers of material bonded together.

Laminated Wood:
Describes an assembly of wood layers in which the wood grain or the fibers of the adjacent layers are parallel. Contrasted with plywood which is characterized by cross layers or cross- crossings, usually alternated with the parallel face, core, and back layers.

A condition where the veneers are so misplaced that one piece overlaps the other rather than making a smooth butt joint.

The machine on which rotary and half round veneer is cut.

The operation of assembling the various layers of veneer or lumber cores after the glue or ad- adhesive has been applied or inserted, and before pressing.

Loose Side:
Refer to TIGHT SIDE.



Return to glossary index

A highly viscous adhesive material applied by trowel to give thick glue lines with gap sealing properties.

Mixer, Glue:
An open drum like vessel with a tapering bottom, provided with revolving blades to stir the mixture. There are two types; with single or double blades on a vertical shaft; and semicircular bars on a horizontal shaft, turning inside of each other.

Any ingredient added to an adhesive formulation that changes its properties.

Modulus of Elasticity:
The ratio of unit stress to unit deformation of a material.

Modulus of Rupture:
The measure of the load necessary to break a material.

Moisture Content:
The amount of water contained in the wood, usually expressed as a percentage of the weight of the oven dry wood.

Moisture Meter:
An instrument for measuring the moisture content of wood.

A relatively simple compound which can react to form a polymer.

An adhesive prepared from a gum and water.



Return to glossary index

Nail Holding:
A measure of the ability of a product to resist the withdrawal of a nail driven into it.



Return to glossary index

Oven Dry Wood:
Wood dried to a constant weight in an oven at or above the temperature of boiling water (usually 101C to 105C or 214F to 221F).

One or more sheets of paper impregnated with resin or high density plastic used as a face material usually for plywood, but sometimes for lumber or other products. The paper-plastic materials, when properly molded to the surface of the plywood, form as an integrated part of the panel and cannot be peeled off. Overlays can be classified as masking, decorative, or structural depending on their purpose.



Return to glossary index

A sheet of manufactured wood product, usually in a standard size such as 4' x 8', in thickness from 1/8" to 4" or can be thicker to 6". A panel can be smaller or larger sheet. A panel can be milled or set into a frame such as a door.

A highly viscosity adhesive composition having a high yield value and usually prepared from starch and water.

Insertions of sound wood, placed and glued into veneer or plywood panels, from which de- defected portions have been removed.

  Boat Patches
  shall be oval-shaped but sides shall taper each direction to a point or a small rounded end; in A faces the rounded ends shall have a radius not exceeding 1/8 inch.

  Router Patches
  shall have parallel sides and rounded ends.

  Sled Patches
  shall be rectangular with feather ends.

The trade name of a log, selected and suitable for cutting into rotary veneer. Applies particularly to softwood.

The entering of an adhesive into an adherent.

The resistance of an adhesive joint to deterioration.

A measure of acidity or alkalinity on a scale of 1 to 14 with 7 being neutral.

Pick Up Roll:
A device for picking up adhesive from a reservoir and transferring it to a spreading mechanism.

Pitch Pocket:
An opening extending parallel to the annual growth rings usually containing pitch.

Pitch Streak:
A well defined accumulation of pitch in a more or less regular streak.

The small, soft core occurring in a structural center of a tree, trunk, branch, twig, or log.

The pressure bearing plates of the hot or cold press which exert or receive pressure. Usually of rolled steel, and in the case with heat platens drilled holes in intersecting gridiron patterns, for steam distribution.

Sound wood of various shapes including, among others, circular, dogbone, and leaf shapes, for replacing defective portions of veneers. Plugs usually are held in veneer by friction only.

The removal of a defect from a wood product and the replacement of it with sound wood or filler to upgrade the product.

A sheet or layer of veneer.

An assembled product, made of layers of veneer and/or lumber and adhesive, the chief characteristic of which is the alternate cross layers, distributing the longitudinal wood strength. This product cannot be split, and shrinkage and swelling, under the influence of moisture, is reduced to a minimum.

This process builds up the molecular size of resin by bringing together molecules of the resin. In general, thermosetting resins, used as plywood adhesives, cure by a combination of con- condensation and polymerization. Frequently called the cure of the resin.

The density of an adherent surface; the property of adhesive absorption by the adherent surface.

Post Cure:
Additional curing of the bond in the stack after pressing has been completed.

Pot Life (Working Life):
The period of time during which an adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remains suitable for use.

The setting of an adhesive, in an assembly, before sufficient pressure for proper bonding is applied to that assembly.

A hydraulic, single opening, cold press designed to compact a press load of plywood panel assemblies prior to hot pressing to permit easy loading of the panels into the hot press.

An agent added to a product to keep the finished product free from decay.

Press, Cold:
A hydraulic or screw press in which the glued members are forced together. The pressure is maintained, after removal from the press, by clamping the bale or bundle of glued members between head-blocks, with clamp irons and turnbuckle rods.

Press, Hot:
A single or multi-platen hydraulic press, with plates or platens, heated by stem, for thermo- setting resin adhesives. May be equipped with water connections to provide for circulating cooling water in the steam areas.

Press, Screw:
A simple form of press in which the manual or mechanical turning of a screw or of a nut exerts the pressure required to bond layers of veneer and lumber into plywood or laminated wood. Used only for cold pressing. Regulation of pressure is difficult.

Press Time:
The time which the assembly to be bonded remains under the pressure necessary for bonding.

Pressing Tolerance:
The difference between the net finished panel thickness and the additional caliper allowed in pressing to compensate for unevenness of the press platens or cauls.

An adherent surface coating applied before the adhesive to improve bond performance.

An instrument used to measure added temperature.



Return to glossary index




Return to glossary index

Rate of Growth:
The rate at which a tree has added wood, measured radially in the trunk or in wood cut from the trunk. The unit of measure in use is number of annual growth rings per inch.

Release Agent:
A material which prevents adhesion.

Any patch, plug, or shim in a plywood panel.

A material, made synthetically, which is the basis for products called plastics. Certain resins can be used to adhere pieces of wood, and these are called resin adhesives, or "resin glues". These adhesives are of relatively recent development and much more durable than the older types of conventional glues.

  Melamine Resins
  a colorless crystalline substance derived from dicyandiamide when joined with formaldehyde forms a resin suitable for coatings, adhesives, and castings.

  Phenolic Resin Adhesives
  are made from chemicals of the phenol group and formaldehyde and normally require heat to cure. Are the very durable. They are available in liquid, powder, and film form. Special types, mixed with suitable accelerators, harden at a moderate tempera- temperatures.

  Resorcinol Resins
  are a type of phenolic resins, but will cure at room, as well as, with the elevated temperatures.

  Urea Resin Adhesives
  are made from urea and formaldehyde, harden when heated and in the presence of certain chemical (catalysts or hardeners); this hardening can be rapid and at moderate temperatures.

The study of deformation and flow behavior of material under stress.

Roll Coater:
Equipment for application of adhesives.

Rotary Cut
A manner of cutting veneer, by which the entire log or block is mounted in a lathe and turned against a broad cutting knife, which is inclined into the log at a slight angle. The veneer is cut in a continuous sheet, from the circumference of the block, somewhat as paper unwound from a roll.



Return to glossary index

Run or flow of adhesive from an adherent surface due to application of excess or low viscosity material.

The living wood of pale color near the outside of the log. Under most conditions, the sapwood is more susceptible to decay than heartwood.

A gap-filling material to prevent excessive absorption of adhesive or penetration of liquid or gaseous substances.

A material which bonds to itself.

More commonly applied to the hardening of a pressed glue. It is brought about either by gel- gelation, by evaporation of the solvent, by chemical polymerization, or by a combination of these factors, with or without heat. It is less generally applied to hot pressed resin adhesives.

Setting Time:
The period of time during which an assembly is subjected to heat or pressure, or both, to set the adhesive.

Shear Strength:
The breaking resistance of a specimen when prepared and broken in tension or com- compression in accordance with a standard test method. This value when in pounds, is usually expressed as psi.

A single ply or layer of veneer.

Shelf Life:
Synonymous with storage life.

A long, narrow repair not more than 3/6 inch wide.

Shop Grade:
Panels which have been rejected as not conforming to grade requirements of standard grades in the Product or Commercial Standards.

A manner of cutting veneer, by which logs or sawn flitches are held securely against a table in a slicing machine. The table is moved down, and at an angle, across a sturdy knife, which shears off the veneer in sheets.

The ability of an adhesive to accommodate adherent movement or repositioning after application to adherent surfaces.

Softening Point:
The temperature at which an adhesive commences to flow or soften.

Generally, one of the botanical groups of trees that in most cases have needlelike or scale- like leaves; the conifers, also the wood produced by such trees. Generally, they do not lose their leaves in the winter. The term has no reference to the actual hardness of the wood.

Solid Core:
The inner ply construction consists of a single uniform material without voids or defects.

Solids Content:
The percentage by weight of nonvolatile matter in an adhesive.

The liquid in which a glue or adhesive is dispersed.

Soybean Meal:

Specific Gravity:
The ratio of the weight of a body to the weight of an equal volume of water at 4C, or other specified temperature.

A machine used for joining sheets of veneer together edge to edge.

Complete separation of veneer fibers parallel to grain, caused chiefly by manufacturing process or handling.

A tool or machine designed to lay out, cover with a layer, or coat a surface to be glued with an adhesive.

The portion of the annual growth ring of a tree that is formed during the early part of the seasons growth. It is usually less dense and weaker mechanically than the summerwood.

Squeeze Out:
The bead of glue squeezed out at the edge or end of a glue joint when pressure is applied.

A discoloration in wood that may be caused by such diverse agents as micro-organisms, metal, or chemicals. The term also applies to materials used to impart color to wood.

Pieces of metal used to hold the platens of a press apart at a desired thickness.

Storage Life:
The period of time during which a packaged adhesive can be stored under specified tempera- temperature conditions and remain suitable for use. Sometimes called shelf life.

The term in its broader sense embraces collectively all the properties of wood that enable it to resist different forces or loads. In its more restrictive sense, strength may apply to any one of the mechanical properties, in which event the name of the property under consideration should be stated, thus; strength in compression parallel to grain, strength in bending, hardness, and similar properties.

The force per unit area resulting from an applied load.

Synonymous with adherent.

Substained Test Load:
A test for the assessment of adhesive performance when placed under stress for an extended period.

The portion of the annual growth ring that is formed after the springwood formation has ceased. It is usually denser and stronger mechanically than springwood.

Symmetrical Construction:
Plywood panels in which the plies on one side of a center ply or core are essentially equal in thickness, grain direction, properties, and arrangements to those on the other side of the core.

The exudation of liquid by gels upon standing.



Return to glossary index

The property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and adherent are brought into contact under low pressure.

The strip of gummed paper or cloth used to hold the edges together at the joint, previous to gluing.

Tapeless Splicer:
A machine used for gluing sheets of veneer together, edge to edge, without the use of gummed tape.

The visible transmissions of faults, imperfections, and patterned striations occurring in an layer of a laminate structure.

Temperature, Curing:
The temperature to which an adhesive or an assembly is subjected to cure the ad- adhesive.

Temperature, Setting:
The temperature to which an adhesive or an assembly is subjected to set the ad- adhesive.

Tests, Accelerated:
The testing of materials by exposure to intensified simulation of service conditions, e.g. weathering, radiation.

Testing Agency:
A commercial organization set up for the purpose of certifying, through an organized testing program, that products manufactured in a particular plant meet the requirements set forth in the appropriate standard. Testing agencies for plywood include such organizations as: The American Ply- wood Association (APA). Timber Engineering Company (TECO), Product Fabrication Service (PFS) Pittsburgh Testing Laboratories, and the General Testing and Inspection Agency, Inc.

Tests, Destructive:
Test involving the destruction of assemblies in order to evaluate the maximum per- performance of the adhesive bond.

Tests, Non-Destructive:
Inspection tests for the evaluation of bond quality without damaging the assembly, e.g. ultrasonics, visual inspections.

A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between springwood and summerwood.

A glue or resin having the property of softening or fusing when heated and of hardening again when cooled.

Thermosetting Glues and Resins:
Glues and resins that are cured by heat, but do not soften when sub- subjected to high temperatures.

A liquid added to an adhesive to modify the consistency or other properties.

Referring to a liquid whose viscosity is lowered under agitation and which returns to the original viscosity upon rest.

Tight Side:
This term, and its opposite, loose side, are used to refer to veneer cut with a knife. A wedge- shaped or beveled knife is used, and the veneer comes out curved way from the knife, thus producing small ruptures on the concave side, known as the loose side. The opposite surface, slightly in compression, but free from any ruptures, is known as the tight side.

Torn Grain:
A marked leafing or separation on veneer surface between spring and summerwood.

The effectiveness of a poisonous material relating to its concentration.

A distortion caused by the turning or winding of a panel or board so that the four corners of any faced are no longer in the same plane.



Return to glossary index

U stands for: Under Construction, Sorry


Return to glossary index

V - P Test:
Abbreviation for vacuum pressure test. Test specimens are submerged in water in a pressure vessel. Vacuum and pressure are then applied alternately before the specimens are removed for further testing.

A thin sheet or layer of wood, sliced, rotary-cut, half round, or sawed from a log, block, or flitch. Veneer is the raw material from which plywood and laminated wood are assembled. Thicknesses may vary from 1/100 to 1/4 inch, and are seldom thicker.

Veneer Grade:
A measure of veneer quality based on freedom from defects, as set forth in an appropriate Product Standards.

An instrument that measures the viscosity of a liquid.

The internal frictional resistance of an adhesive to flow when the resistance is directly proportional to the applied force. (Measure of consistency).

Used to describe a substance that evaporates readily.



Return to glossary index

Any variation from a true or plane surface. Warp includes bow, cup, and twist, or any combination thereof.

As applied to plywood, the term is synonymous with EXTERIOR; that is, plywood, bonded with adhesives capable of withstanding prolonged exposure to severe service conditions without failure in the glue bonds.

Water Resistant:
A term frequently applied to plywood, bonded with moderately resistant adhesives, capable to withstanding limited exposure to water or to severe conditions without failure in the glue bonds.

The mechanical or chemical disintegration and discoloration of the surface of wood caused by exposure to light, the action of dust of sand carried by winds, and the alternate shrinking and swelling of the surface fibers due to the continual variation in moisture content brought about by changes in the weather. Weathering does not include decay.

The relative ability of a liquid adhesive to display inter-facial affinity for an adherent and to flow uniformly over the adherent surface.

Wood Failure:
The rupturing of wood fibers in strength rests of bonded specimens, usually expressed as the percentage of the total area involved which shows failure.

Working Life (Of Resin Adhesives):
The period during which a mixture of resin adhesive remains suit- able for spreading before hardening in the receptacle, or commencing to jell appreciably.



Return to glossary index

X stands for: X-nay on the entry- ay


Return to glossary index

The amount of veneer converted to a standard plywood thickness cut from a block expresses as a ratio of the scale of the block.



Return to glossary index

Z stands for: Zero entries, sorry