Woodworking Glossary
"A"
Absorption:
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.
Adherent:
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.
Adhesive:
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.
Affinity:
The attraction between adhesive and adherent.
Albumin, Blood:
See GLUE
Aliphatic:
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.
Alligatoring:
(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.
Amylaceous:
Pertaining to or nature of starch.
Animal Glue:
See 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.
Applicator:
A device used to spread an adhesive as a film of the desired
thickness.
Aqueous:
Water based or containing water.
Aromatic:
Organic compound whose molecules have the carbon atoms arranged in
a ring structure.
Asphalt:
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.
Assembly:
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.
A-Stage:
An early stage in the curing of thermosetting resin when the
material is still fusible and soluble in certain solvents.
Atomize:
The reduction of a liquid to a fine spray by means of high
pressure air or, as in airless spray, by pressure alone.
Autoclave:
A heavy cylindrical vessel equipped for vacuum and/or pressure
application. May have attachment for water supply and application of
heat.
"B"
Back:
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.
Back-Up:
A material placed into a joint, primarily to control the depth of
the sealant.
Backing:
The flexible supporting material for an adhesive, e.g., pressure
sensitive adhesives are commonly backed with paper, plastic films,
or fabrics.
Bactericide:
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.
Bead:
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.
Binder:
The component of an adhesive which is mainly responsible for
adhesive properties.
Bite:
The penetration or dissolution of an adherent surface by an
adhesive.
Bitumen:
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.
Blemish:
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:
See GLUE, ALBUMIN.
Blushing:
Formation of condensation on the surface of a contact adhesive as
the solvent evaporates and its temperature is rapidly lowered.
Boardy:
Adjective applied to stiff inflexible mastic or coating resembling
a board.
Body:
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.
Bolt:
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.
Bow:
The distortion in a panel or board that deviates from flatness
length-wise but not across its faces.
Bubble:
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.
B-Stage:
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.
"C"
"C" Factor: See Thermal Conductance
Casein:
See GLUE.
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.
Catalyst:
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.
Caul:
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.
Cement:
Synonymous with adhesive.
Centers:
Inner plies of a multi-layered product whose grain direction runs
parallel to that of the outer ply.
Centipoise:
One hundredth of a poise; unit of viscosity measure.
Certification:
The act of certifying or attesting; a guarantee that a material
meets certain specifications and so indicated by a stamp of the
testing agency.
Check:
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.
Clipper:
The shearing machine used to dimension green or dry veneers.
Coalescence:
Initial state of film formation in a water base system.
Cobwebbing:
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.
Cohesion:
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.
Collagen:
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.
Colloidal:
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.
Construction:
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.
Co-Polymer:
A polymerization product of two or more different monomers.
Core
(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.
Coverage:
The spreading power of an adhesive over the area of adherent.
Crazing:
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.
Creep:
The dimensional change with time of a material under sustained
load.
Crossbanding:
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.
Cross-Linking:
The union of adjacent molecules of uncured adhesives by catalytic
or curing agents.
C-Stage:
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.
Cure:
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.
Cycle:
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.
"D"
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.
Decay:
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.
Defect:
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.
Dehydrate:
The loss or removal of water from a substance.
Delamination:
Separation of plies; often used in reference to the durability of
the glue line.
Densification:
Increasing the density through compaction during pressing.
Density:
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.
Diluent:
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.
Dispersed:
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:
See GLUE SPREAD.
Drier:
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.
Dryout:
The loss of moisture in a glue spread resulting in a poor bond.
"E"
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.
Elastomer:
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.
Emulsion:
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.
Extender:
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.
Extractives:
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.
Extruder:
Adhesive applicator which extrudes liquid glue from orifices in
the form of beads.
"F"
Face:
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.
Fatigue:
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.
Filler:
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.
Flitch:
A longitudinal section of a log or a bundle of matched veneers.
Flow:
Movement of an adhesive during the bonding process, before the
adhesive is set.
Formaldehyde:
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.
"G"
Gel:
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.
Gelation:
The forming of a gel.
Glue:
A term customarily applied to the older conventional cold
setting adhesives, but now generally accepted as being synonymous
with adhesive.
Glue Types:
Albumin
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.
Grade:
The designation of the quality of a manufactured piece of wood or
of logs.
Grademark:
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.
Grain:
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.
"H"
Hardener:
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.
Hardwood:
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.
Heartwood:
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.
Hygroscopic:
The ability of materials to readily absorb and retain moisture
from the atmosphere.
"I"
Inhibitor:
A material which retards a chemical reaction. Inhibitors are used
to extend the shelf life and pot life of certain adhesives.
Interface:
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.
"J"
Joint:
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.
"K"
Knot:
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.
Knotholes:
Voids produced by the dropping of knots from the wood in which
they are originally embedded.
"L"
Laminate:
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.
Lap:
A condition where the veneers are so misplaced that one piece
overlaps the other rather than making a smooth butt joint.
Lathe:
The machine on which rotary and half round veneer is cut.
Lay-Up:
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.
"M"
Mastic:
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.
Modifier:
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.
Monomer:
A relatively simple compound which can react to form a polymer.
Mucilage:
An adhesive prepared from a gum and water.
"N"
Nail Holding:
A measure of the ability of a product to resist the withdrawal of
a nail driven into it.
"O"
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).
Overlays:
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.
"P"
Panel:
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.
Paste:
A highly viscosity adhesive composition having a high yield value
and usually prepared from starch and water.
Patches:
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.
Peeler:
The trade name of a log, selected and suitable for cutting into
rotary veneer. Applies particularly to softwood.
Penetration:
The entering of an adhesive into an adherent.
Permanence:
The resistance of an adhesive joint to deterioration.
pH:
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.
Pith:
The small, soft core occurring in a structural center of a tree,
trunk, branch, twig, or log.
Platens:
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.
Plug:
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.
Plugged:
The removal of a defect from a wood product and the replacement of
it with sound wood or filler to upgrade the product.
Ply:
A sheet or layer of veneer.
Plywood:
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.
Polymerization:
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.
Porosity:
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.
Precure:
The setting of an adhesive, in an assembly, before sufficient
pressure for proper bonding is applied to that assembly.
Prepress:
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.
Preservative:
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.
Primer:
An adherent surface coating applied before the adhesive to improve
bond performance.
Pyrometer:
An instrument used to measure added temperature.
"Q"
"R"
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.
Repair:
Any patch, plug, or shim in a plywood panel.
Resin:
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.
Rheology:
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.
"S"
Sagging:
Run or flow of adhesive from an adherent surface due to
application of excess or low viscosity material.
Sapwood:
The living wood of pale color near the outside of the log. Under
most conditions, the sapwood is more susceptible to decay than
heartwood.
Sealant:
A gap-filling material to prevent excessive absorption of adhesive
or penetration of liquid or gaseous substances.
Self-Adhesive:
A material which bonds to itself.
Setting:
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.
Sheet:
A single ply or layer of veneer.
Shelf Life:
Synonymous with storage life.
Shim:
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.
Sliced:
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.
Slip:
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.
Softwoods:
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.
Solvent:
The liquid in which a glue or adhesive is dispersed.
Soybean Meal:
See GLUE.
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.
Splicer:
A machine used for joining sheets of veneer together edge to edge.
Split:
Complete separation of veneer fibers parallel to grain, caused
chiefly by manufacturing process or handling.
Spreader:
A tool or machine designed to lay out, cover with a layer, or coat
a surface to be glued with an adhesive.
Springwood:
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.
Stain:
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.
Stops:
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.
Strength:
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.
Stress:
The force per unit area resulting from an applied load.
Substrate:
Synonymous with adherent.
Substained Test Load:
A test for the assessment of adhesive performance when placed
under stress for an extended period.
Summerwood:
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.
Syneresis:
The exudation of liquid by gels upon standing.
"T"
Tack:
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.
Tape:
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.
Telegraphing:
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.
Texture:
A term often used interchangeably with grain. Sometimes used to
combine the concepts of density and degree of contrast between
springwood and summerwood.
Thermoplastic:
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.
Thinner:
A liquid added to an adhesive to modify the consistency or other
properties.
Thixotropic:
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.
Toxicity:
The effectiveness of a poisonous material relating to its
concentration.
Twist:
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.
"U"
U stands for: Under Construction, Sorry
"V"
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.
Veneer:
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.
Viscometer:
An instrument that measures the viscosity of a liquid.
Viscosity:
The internal frictional resistance of an adhesive to flow when the
resistance is directly proportional to the applied force. (Measure
of consistency).
Volatile:
Used to describe a substance that evaporates readily.
"W"
Warp:
Any variation from a true or plane surface. Warp includes bow,
cup, and twist, or any combination thereof.
Waterproof:
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.
Weathering:
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.
Wetting:
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.
"X"
X stands for: X-nay on the entry- ay
"Y"
Yield:
The amount of veneer converted to a standard plywood thickness cut
from a block expresses as a ratio of the scale of the block.
"Z"
Z stands for: Zero entries, sorry
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