The science of sound and sound control.
The property of a coating or sealant to bond to the surface
to which it is applied.
Loss of bond of a coating or sealant from the surface to
which it was applied.
The amount of air leaking in and out of a building through
cracks in walls, windows and doors.
In the manufacturing of float glass, it is the process of
controlled cooling done in a lehr to prevent residual stresses
in the glass. Re-annealing is the process of removing
objectionable stresses in glass by re-heating to a suitable
temperature followed by controlled cooling.
An in-line, controlled heating/cooling apparatus located
after the tin bath and before the cooling conveyor of a float
glass production line. Its purpose is to relieve induced stress
from the flat glass product to allow normal cold end processing.
Elastomeric blocks that limits lateral glass movement in the
glazing channel, which may result from thermal, seismic, wind
load effects, building movement, and other forces that may
The quotient of the long side of a glazing lite over the
short side of that lite.
A vessel that employs high-pressure and heat. In the glass
industry, used to produce a bond between glass and PVB or
urethane sheet, creating a laminated glass product.
A polyethylene or polyurethane foam material installed under
compression and used to control sealant joint depth, provide a
surface for sealant tooling, serve as a bond breaker to prevent
three-sided adhesion, and provide an hour-glass contour of the
Back Putty (See Bed or Bedding)
A material placed into a joint to control the depth of the
sealant and to prevent adhesion at the base of the sealant bead.
An applied sealant 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.
Bed or Bedding
In glazing, the bead of compound or sealant applied between
a lite of glass or panel and the stationary stop or sight bar of
the sash or frame. It is usually the first bead of compound or
sealant to be applied when setting glass or panels.
Bedding of Stop
In glazing, the application of compound or sealant at the
base of the channel, just before the stop is placed in position,
or buttered (see Buttering) on the inside face of the stop.
Flat glass that has been shaped while hot into curved
Bevel of Compound Bead
In glazing, a bead of compound applied to provide a slanted
top surface so that water will drain away from the glass or
The process of edge finishing flat glass to a bevel angle.
The dimension by which the framing system overlaps the edge
of the glazing infill.
A migration of a liquid to the surface of a component or
into/onto an adjacent material.
A profusion of bubbles in a coating film that form during
the heat-treating process and remain after the film solidifies.
Rectangular, cured sections of EPDM, neoprene, silicone or
other suitable material, used to position the glass product in
the glazing channel.
Bow (and Warp)
A curve, bend or other deviation from flatness in glass.
Breather Tube Units (See also Capillary
An insulating glass unit with a tube and/or hole
factory-placed into the unitís spacer to accommodate pressure
differences encountered in shipping due to change in elevation.
The tube and/or hole are to be properly sealed on the jobsite
prior to unit installation. Consult IG unit fabricator.
In laminated glass, a gas pocket in the interlayer material
or between the glass and the interlayer. In float glass, a
gaseous inclusion greater than 1/32" (.8 mm) in diameter.
Open or closed pockets in a sealant caused by release,
production, or expansion of gasses.
In float glass manufacture, the extreme lateral edge of the
ribbon as drawn.
Bullet Resistant Glass
A multiple lamination of glass or glass and plastic that is
designed to resist penetration from medium-to-super-power small
arms and high-power rifles.
Application of sealant or compound to the flat surface of
some member before placing the member in position, such as the
buttering of a removable stop before fastening the stop in
The installation of glass products where the vertical glass
edges are without structural supporting mullions.
Capillary Tube Units (See
also Breather Tube Units)
An insulating glass unit with a very small inside diameter metal
tube of specific length factory-placed into the unitís spacer to
accommodate pressure differences encountered in shipping because
of substantial changes in elevation and the pressure differences
encountered daily after installation. Capillary tubes may or may
not require sealing prior to installation. Consult IG unit
(v) The application of a sealant to a joint, crack or
(n) A compound used for sealing that has minimum joint
movement capability; sometimes called low performance sealant.
Channel (See Pocket)
The installation of glass products into U-shaped glazing
channels. The channels may have fixed stops; however, at least
one glazing stop on one edge must be removable.
The distance between opposing glazing stops.
Very small cracks in flat glass, usually at the edge.
Chemically Strengthened Glass
Glass that has been strengthened by ion-exchange to produce
a compressive stress layer at the treated surface.
An imperfection due to breakage of a small fragment from the
cut edge of the glass. Generally this is not serious except in
heat absorbing glass.
Wire spring devices used to hold glass in rabbeted sash,
without stops, and face glazed.
Internal splitting of a compound resulting from
over-stressing of the compound.
The ability of two or more materials to exist in close and
permanent association for an indefinite period with no adverse
effect of one on the other.
A chemical formulation of ingredients used to produce a
caulking, elastomeric joint sealant, etc.
A gasket designed to function under compression.
The permanent deformation of a material after removal of the
The appearance of moisture (water vapor) on the surface of
an object caused by warm moist air coming into contact with a
Degree of softness or firmness of a compound as supplied in
the container and varying according to method of application,
such as gun, knife, tool, etc.
Coolness Index (See Luminous Efficacy)
A lightly pitted area on glass resulting in a dull gray
Broken glass, excess glass from a previous melt or edges
trimmed off when cutting glass to size. Cullet is an essential
ingredient in the raw batch in glass-making because it
One part of a multi-part sealant which when added to the
base will cause the base to change its physical state by
chemical reaction between the two parts.
Glass cut to specified width and length.
Tool used in cutting glass.
Scoring glass with a diamond, steel wheel or other hard
alloy wheel and breaking it along the score. Other methods of
cutting glass include water jet and laser.
Deflection (framing member)
The amount of bending movement of any part of a structural
member perpendicular to the axis of the member under an applied
Deflection (center of glass)
The amount of bending movement of the center of a glass lite
perpendicular to the plane of the glass surface under an applied
Specified pressure a product is designed to withstand.
Scattering, dispersing, as the tendency to eliminate a
direct beam of light.
Deep, short scratches.
Alteration of viewed images caused by variations in glass
flatness or inhomogeneous portions within the glass. An inherent
characteristic of heat-treated glass.
In general, any use of two lites of glass, separated by an
air space, within an opening, to improve insulation against heat
transfer and/or sound transmission. In insulating glass units
the air between the glass sheets is thoroughly dried and the
space is sealed, eliminating possible condensation and providing
superior insulating properties.
In float glass, approximately 1/8" (3 mm) thick.
Also called compression glazing, a term used to describe
various means of sealing monolithic and insulating glass in the
supporting framing system with synthetic rubber and other
elastomeric gasket materials.
Accomplishment of weather seal between glass and sash by use
of strips or gaskets of Neoprene, EPDM, silicone or other
flexible material. A dry seal may not be completely watertight.
The measurement of hardness of a material. (See also Shore A
Hardness) A gauge to measure the hardness of an elastomeric
Ethylene Propylene Diene Monomer, a synthetic rubber.
Edge Block (See Anti-walk Block)
Nominal spacing between the edge of the glass product and
the bottom of the glazing pocket (channel).
Grinding the edge of flat glass to a desired shape or
An elastic, rubber-like substance, such as natural or
(adj) Having the property of returning to its original shape
and position after removal of load.
(n) An elastic rubber like substance.
The measure of a surfaceís ability to emit long-wave
To alter the surface of glass with hydrofluoric acid or
other caustic agents. Permanent etching of glass may occur from
alkali and other runoff from surrounding building materials.
Glazing infills set from the exterior of the building.
The molding or bead that holds the lite or panel in place
when it is on the exterior side of the lite or panel.
The whole exterior side of a building that can be seen at
one view; strictly speaking, the principal front. Commonly used
as reference to the exterior skin of a building.
A system having a triangular bead of compound applied with a
putty knife, after bedding, setting and clipping the glazing
infill in place on a rabbetted sash.
Any glazed panel, window, door, curtain wall or skylight
unit on the exterior of a building.
Figured Glass (See Patterned Glass)
Caulking or sealant placed in such a manner that it forms an
angle between the materials being caulked.
To make glass smooth or glossy by the action of fire or
The period of time that an opening protective assembly will
maintain the ability to confine a fire as determined by tests Ė
NFPA 252/ NFPA 257/UL 9/UL 10c/ASTM E 2010/ASTM E 2074.
That property of materials or their assemblies that prevents
or retards the passage of excessive heat, hot gases or flames
under conditions of use.
The period of time a building element, component or assembly
maintains the ability to confine a fire, continues to perform a
given structural function, or both, as determined by tests Ė
NFPA 251/ASTM E 119/UL 263 (wall assemblies).
A protrusion on the edge of a lite of glass.
A general term that describes float glass, sheet glass,
plate glass and rolled glass.
Glass formed on a bath of molten tin. The surface in contact
with the tin is known as the tin surface or tin side. The top
surface is known as the atmosphere surface or air side.
Flush Glazing (Pocket Glazing)
The setting of a lite of glass or panel into a four-sided
sash or frame opening containing a recessed "U" shaped channel
without removable stop on three sides of the sash or frame and
one channel with a removable stop along the fourth side.
A surface treatment for glass, consisting of an acid etching
of one or both surfaces that diffuses transmitted light and
Fully Tempered Glass
Flat or bent glass that has been heat-treated to have either
a minimum surface compression of 10,000 psi (69 MPa) or an edge
compression not less than 9,700 psi (67 MPa) in accordance with
the requirements of ASTM C 1048, kind FT or meet the
requirements of ANSI Z97.1 or CPSC 16 CFR 1201. Outside of North
America, sometimes called "toughened glass."
Insulating glass units with a gas other than air in the air
space to decrease the unitís thermal conductivity (U-value) or
to increase the unitís sound insulating value.
Pre-formed shapes, such as strips, grommets, etc., of rubber
or rubber-like composition, used to fill and seal a joint or
opening either alone or in conjunction with a supplemental
application of a sealant.
In bent glass, the distance around the concave or convex
surface measured perpendicular to the height, including any
A hard brittle substance, usually transparent, made by
fusing silicates, under high temperatures, with soda, lime, etc.
Glass Clad Polycarbonate
One or more lites of flat glass bonded with an aliphatic
urethane interlayer to one or more sheets of extruded
polycarbonate in a pressure/temperature/vacuum laminating
Minute glass particles typically resulting from glass
fabrication processes (i.e. cutting, grinding, polishing,
drilling, edging, etc.)
Glass Quality (Flat)
Defined by ASTM C 1036 on the basis of end use and allowable
(n) A generic term used to describe an infill material such
as glass, panels, etc.
(v) The process of installing an infill material into a
prepared opening in windows, door panels, partitions, etc.
A strip surrounding the edge of the glass in a window or
door, which holds the glass in place.
A three-sided, U-shaped sash detail into which a glass
product is installed and retained.
Sealant formulated in a degree of viscosity suitable for
application through the nozzle of a caulking gun.
Glass that absorbs an appreciable amount of solar energy.
Glass able to withstand high thermal shock, generally
because of a low coefficient of expansion.
Flat or bent glass that has been heat-treated to have a surface
compression between 3,500 and 7,500 psi (24 to 52 MPa) and meet
the requirements of ASTM C 1048, kind HS. Heat-strengthened
glass is not a safety glazing material and will not meet the
requirements of ANSI Z97.1 or CPSC 16 CFR 1201.
Term used for both fully tempered glass and
Sealant applied at the base of a channel, after setting the
lite or panel and before the removable stop is installed; one of
its purposes being to prevent leakage past the stop.
Glass, which transmits an exceptionally high percentage of
Insulating Glass Unit
Two or more lites of glass spaced apart and hermetically
sealed to form a single-glazed unit with an air space between
each lite. (Commonly called IG units.)
Glazing infills set from the interior of the building.
The removable molding or bead that holds the lite in place
when it is on the interior side of the lite.
Any material used to bond two lites of glass and/or plastic
together to form a laminate.
The vertical frame members at the perimeter of the opening.
The space or opening between two or more adjoining surfaces.
An abrupt deviation from a flat plane or the normal contours
of bow and warp, and most commonly found near the edge of a
piece of heat-treated glass.
Compound formulated in a degree of firmness suitable for
application with a putty knife such as used for face glazing and
other sealant applications.
Knocked Down (KD)
Fabricated framing components shipped loose for assembly at
Two or more lites of glass permanently bonded together with
one or more interlayers.
Laminated Plastics (Plastic Laminates)
Two or more lites (or sheets) of polycarbonate (or acrylic)
with an aliphatic urethane interlayer between polycarbonate or
acrylic bonded together under heat and pressure.
A long, tunnel-shaped oven for annealing glass, usually by a
Another term for a pane of glass. Sometimes spelled "light"
in the industry literature, but spelled "lite" in this text to
avoid confusion with light as in "visible light".
Loads produced by the use and occupancy of the building or
other structure and do not include construction or environmental
loads such as wind load, snow load, ice load, rain load, seismic
load or dead load.
Low-emissivity (or low-e)
A low rate of emitting (radiating) absorbed radiant energy.
The radiant energy (heat), i.e. long wave infrared, is in
effect, reradiated back toward its source.
Luminous Efficacy (Light-to-Solar Gain
The visible transmittance of a glazing system divided by the
solar heat gain coefficient (or shading coefficient). This ratio
is helpful in selecting glazing products for different climates
in terms of those that transmit more heat than light and those
that transmit more light than heat.
Descriptive of heavy-consistency compounds that may remain
adhesive and pliable with age.
Microscopic Surface Particles
Any glass fines, debris, dust, grit, refractory particles,
etc., that are invisible to the naked eye, and that adhere to
one or both glass surfaces during the heat-treating process.
Spreading or creeping of a constituent of a compound
onto/into adjacent surfaces. See bleeding.
Stress at a given strain. Also tensile strength at a given
A horizontal or vertical member that supports and holds such
items as panels, glass, sash, or sections of a curtain wall.
Insulating glass units with three or more lites of glass.
Horizontal or vertical bars that divide the sash frame into
smaller lites of glass. Muntins are smaller in dimensions and
weight than mullions.
A synthetic rubber having physical properties closely
resembling those of natural rubber. It is made by polymerizing
chloroprenes, and the latter is produced from acetylene and
A sealant that does not set up or cure.
A sealant formulation having a consistency that will permit
application in vertical joints without appreciable sagging or
slumping. A performance characteristic, which allows the sealant
to be installed in a sloped or vertical joint application
without appreciable sagging or slumping.
Descriptive of a product that does not form a surface skin.
Characteristic of a compound, which will not stain a
The tubular tip of a caulking gun through which the compound
OITC (Outside-Inside Transmission
A rating used to classify the performance of glazing in
exterior applications. (For more information see ASTM E 1332 and
ASTM E 1425.)
Obscure Glass (See Patterned Glass)
Any compound which consists of carbon and hydrogen with a
restricted number of other elements, such as oxygen, nitrogen,
sulphur, phosphorous, chlorine, etc.
One type of rolled glass having a pattern impressed on one
or both sides. Used extensively for light control, bath
enclosures and decorative glazing. Sometimes called "rolled,"
"figured" or "obscure" glass.
The amount by which a material fails to return to its
original dimensions after being deformed by an applied force or
A three-sided, U-shaped opening in a sash or frame to
receive glazing infill. Contrasted to a rabbet, which is a
two-sided, L-shaped section, as with face glazed window sash.
Pocket (Channel) Depth
The inside dimension from the bottom of the pocket to the
top. Pocket depth equals the bite plus the edge clearance.
Pocket Glazing (See Flush Glazing)
Pocket (Channel) Width
The measurement between stationary stops (or stationary stop
and removable stop) in a U-shaped channel.
Thin, flat, triangular or diamond shaped pieces of zinc used
to hold glass in wood sash by driving them into the wood.
A device for examining the degree of strain in a sample of
Polished Wired Glass
Wired glass that has been ground and polished on both
Typically the primary seal in a dual seal IG unit and the
key component in restricting moisture vapor transmission.
A chemical structure consisting of long chains of molecular
Polysulfide liquid polymer sealant, which are mercaptan
terminated, long chain aliphatic polymers containing disulfide
linkages. They can be converted to rubbers at room temperature
without shrinkage upon addition of a curing agent.
An organic compound formed by the reaction of a glycol with
Polyvinyl Chloride (PVC)
Polymer formed by polymerization of vinyl chloride monomer.
Sometimes called vinyl.
The time interval following the addition of an accelerator
before a chemically curing material will become too viscous to
Pre-Shimmed Tape Sealant
A sealant having a pre-formed shape containing solids or
discrete particles that limit its deformation under compression.
A coating specifically designed to enhance the adhesion of
sealant systems to certain surfaces, to form a barrier to
prevent migration of components, or to seal a porous substrate.
Sealing of a porous surface so that compound will not stain,
lose elasticity, shrink excessively, etc., because of loss of
oil or vehicle into the surround. A sealant primer or surface
conditioner may be used to promote adhesion of a curing type
sealant to certain surfaces.
A process for applying a thin metallic coating to the
surface of flat glass during the float glass manufacturing
An "L" shaped section, which can be face glazed or receive a
removable glazing bead to hold the lite of glass in place.
A movement or distortion of sash or frames causing a change
in angularity of corners.
Glass with a metallic coating to reduce solar heat gain.
(See also Solar Control Glass).
Relative Heat Gain
The amount of heat gain through a glass product taking into
consideration the effects of solar heat gain (shading
coefficient) and conductive heat gain (U-value). The value is
expressed in Btu/hr/ft2 (W/m2).
The relative heat gain is calculated as RHG =
(Summer U-value x 14oF) + (Shading Coefficient x 200). The lower
the relative heat gain, the more the glass product restricts
Removable Double Glazing (RDG)
A removable glazed panel or sash on the inside or outside of
an existing sash or window, such as a storm panel, used for
additional insulation and protection against the elements.
Roll (or Roller) Distortion
Waviness imparted to horizontal heat-treated glass while the
glass is transported through the furnace on a roller conveyor.
The waves produce a distortion when the glass is viewed in
Indentations in the surface of rolled glass that are caused
by contact of the glass with the rolls and/or displaced roll
disks while the glass surface is in a plastic state.
Roll Marks (also Roll Scratches)
A series of the fine parallel scratches or tears on the surface
of rolled glass in the direction of draw. They are 1/8" (3 mm)
long or smaller, but usually so fine and so close together that
they appear to be a series of incipient checks rather than
scratches. They are caused by a difference in velocity between
rolls and the sheet of glass.
Glass formed by rolling, including patterned and wired glass.
The opening in a wall into which a door or window is to be
A series of small scratches in glass generally caused during
transport by a chip lodged between two lites.
The thermal resistance of a glazing system expressed ft2/hr/oF/Btu
(m2/W/oC). The R-value is the reciprocal of the U-value. The
higher the R-value, the less heat is transmitted throughout the
STC (Sound Transmission Class)
A single number rating derived from individual transmission
losses at specified test frequencies (for more information see
ASTM E 90 and ASTM E 413). It is used for interior walls,
ceilings and floors and in the past was also used for
preliminary comparison of the performance of various glazing
STL (Sound Transmission Loss)
The reduction of the amount of sound energy passing through
a wall, floor, roof, etc. It is related to the specific
frequency (Hz) at which it is measured and it is expressed in
decibels (dB). Also called "Transmission Loss (TL)."
A surface treatment for flat glass obtained by spraying the
glass with hard particles to roughen one or both surfaces of the
glass. The effect is to increase obscurity and diffusion, but it
makes the glass weaker and harder to clean.
The window frame, including muntin bars if used, to receive
the glazing infill.
To penetrate the surface of a lite of glass by means of a
cutting device, e.g. a glass cutter, along a predetermined line
in order to produce a lite of glass of a specific size and/or
Any marking or tearing of the surface appearing as though it
had been done by either a sharp or rough instrument.
Screw-On Bead (or Applied Stop)
Stop, molding or bead fastened by screws as compared with
those that snap into position without additional fastening.
An elastomeric material with adhesive qualities, applied
between components of a similar or dissimilar nature to provide
an effective barrier against the passage of the elements.
Sealed Insulating Glass Units (See
Insulating Glass Unit)
To grind, usually with an abrasive belt, wet or dry, the sharp
edges of a piece of glass.
Minute bubbles in float glass less than 1/32" (.8 mm) in
Placement of lites or panels in sash or frames. Also action
of a compound as it becomes more firm after application.
Generally rectangular, cured extrusions of neoprene, EPDM,
silicone, rubber or other suitable material on which the glass
product bottom edge is placed to effectively support the weight
of the glass.
The ratio of the solar heat gain through a specific glass
product to the solar heat gain through a lite of 1/8" (3mm)
clear glass. Glass of 1/8" (3mm) thickness is given a value of
1.0; therefore, the shading coefficient of a glass product is
calculated as follows:
Solar Heat Gain of the Glass in
Question = S.C.
Solar Heat Gain of 1/8" Clear Glass
A device for inspecting glass with respect to distortion and
Used in the glazing and sealant business to refer to the
length of time a product may be stored before beginning to lose
its effectiveness. Manufacturers usually state the shelf life
and the necessary storage conditions on the package.
Shims (See Spacers)
Shore "A" Hardness
Measure of firmness of a compound by means of a Durometer
Hardness Gauge (Shore A hardness range of 20-25 is about the
firmness of an art gum eraser. A hardness of 90 is about the
firmness of a rubber heel).
The line along perimeter of glazing infills corresponding to
the top edge of stationary and removable stops. The line to
which sealants contacting the glazing infill are sometimes
A sealant having as its chemical composition a backbone
consisting of alternating silicon-oxygen atoms.
Any installation of glass that is at a slope of 15 degrees
or more from vertical.
Streaked areas appearing as slight discoloration on glass.
Solar Control Glass
Tinted and/or coated glass that reduces the amount of solar
heat gain transmitted through a glazed product.
Solar Energy Reflectance
In the solar spectrum, the percentage of solar energy that
is reflected from the glass surface(s).
Solar Energy Transmittance
The percentage of ultraviolet, visible and near infrared
energy within the solar spectrum (300 to 2100 nanometers) that
is transmitted through the glass.
Solar Heat Gain Coefficient
The ratio of the solar heat gain entering the space area
through the fenestration product to the incident solar
radiation. Solar heat gain includes directly transmitted solar
heat and absorbed solar radiation, which is then reradiated,
conducted, or convected into the space.
Change in transmission, and sometimes color, of plastics as
a result of exposure to sunlight or other radiation.
Sound Transmission Class (See STC)
Sound Transmission Loss (See STL)
Small blocks of neoprene, EPDM, silicone or other suitable
material, placed on each side of the glass product to provide
glass centering, maintain uniform width of sealant bead and
prevent excessive sealant distortion.
The panel(s) of a wall located between vision areas of
windows, which conceal structural columns, floors and shear
Spectrally Selective Glass
Tinted and/or coated flat glass that reduces the amount of
solar heat gain transmitted through a glazed product.
Sputtering (See Vacuum (Sputtering)
Discoloration of either a glass or finished aluminum surface
caused by alkalis that leach from surrounding materials such as
pre-cast or cast-in-place concrete or from sealants, pollutants
or other contaminants.
Any crystalline inclusion imbedded in the glass.
Either the stationary lip or the removable molding of the
rabbet, serving to hold the glazing infill in the sash or frame,
with the help of spacers.
A panel or sash door placed on the outside of an existing
door to provide additional protection from the elements.
A glazed panel or sash placed on the inside or outside of an
existing sash or window as additional protection against the
The percentage of elongation or compression of a material or
portion of a material caused by an applied force.
A specific geometric pattern of iridescence or darkish
shadows that may appear under certain lighting conditions,
particularly in the presence of polarized light (also called
quench marks). The phenomenon is caused by the localized
stresses imparted by the rapid air cooling of the tempering
operation. Strain pattern is characteristic of heat-treated
Any condition of tension or compression existing within the
glass, particularly due to incomplete annealing, temperature
gradient, or inhomogeneity.
The operation of smoothing off excess compound or sealant at
sight line when applying same around lites or panels.
Structural Glazing Gaskets
Cured elastomeric channel-shaped extrusions used in place of
a conventional sash to install glass products onto structurally
supporting sub-frames, with the pressure of sealing exerted by
the insertion of separate lockstrip wedging splines.
Structural Silicone Glazing
The use of a silicone sealant for the structural transfer of
loads from the glass to its perimeter support system and
retention of the glass in the opening.
A base material to which other materials or fabrication
procedures are applied.
A sealant having a pre-formed shape, and intended to be used
in a joint under compression.
Tempered Glass (See Fully Tempered Glass)
The relative ability of glass to withstand thermal shock.
Glass with colorants added to the basic glass batch that
give the glass color, as well as, light and heat-reducing
capabilities. The color extends throughout the thickness of the
glass. Typical colors include bronze, gray, dark gray,
aquamarine, green, deep green, blue and black.
Sealant applied at the intersection of the outboard glazing
stop and the bottom of the glazing channel; must be sized to
also provide a seal to the edge of the glass.
Small, surface indentations near and parallel to one edge of
vertically-tempered or vertically heat-strengthened glass
resulting from the tongs used to suspend the glass during the
heat treating process.
The operation of pressing in and striking a sealant in a
joint, to press the sealant against the sides of a joint and
secure good adhesion; the finishing off of the surface of a
sealant in a joint so that it is flush with the surface.
International terminology for fully tempered glass. (See
Fully Tempered Glass)
The ability of the glass to pass light and/or heat, usually
expressed in percentages (visible transmittance, thermal
Two-Part (Multi-Component) Sealant
A product comprised of a base and curing agent or
accelerator, necessarily packaged in two separate containers,
which are uniformly mixed just prior to use.
The name of the invisible portion of the light spectrum with
wavelengths shorter than 390 nanometers.
Term normally used to refer to one single assembly of
Total of one width and one height of a lite of glass in
A measure of air-to-air heat transmission (loss or gain) due
to the thermal conductance and the difference in indoor and
outdoor temperatures. As the U-value decreases, so does the
amount of heat that is transferred through the glazing material.
The lower the U-value, the more restrictive the fenestration
product is to heat transfer. Reciprocal of R-value.
Vacuum (Sputtering) Deposition
Process for applying multiple layers of metallic coatings to
the surface of flat glass in a vacuum chamber.
Vents (See Checks)
Holding glass in place with extruded vinyl channel or roll-in
Visible Light Reflectance
The percentage of visible light (390 to 770 nanometers)
within the solar spectrum that is reflected from the glass
Visible Light Transmittance
The percentage of visible light (390 to 770 nanometers)
within the solar spectrum that is transmitted through glass.
Warp (See Bow
An optical effect in flat glass due to irregularities in the
surface of the glass that make objects viewed at various angles
appear wavy or bent.
Weathering (also Stain)
Attack of a glass surface by atmospheric elements.
A material or device used to seal the opening between sash
and/or sash and frame.
Weeps (or Weep Holes)
Drain holes or slots in the sash or framing member to
prevent accumulation of condensation and water.
Application of an elastomeric sealant between the glass and
sash to form a weather-tight seal.
An opening constructed in a wall or roof and functioning to
admit light or air to an enclosure, usually framed and spanned
with glass mounted to permit opening and closing.
Rolled glass having a layer of meshed or stranded wire
completely imbedded as nearly as possible to the center of
thickness of the lite. This glass is available as polished glass
(one or both surfaces) and patterned glass. Approved polished
wired glass is used as transparent or translucent fire
protection rated glazing. Patterned wired glass is sometimes
used as decorative glass. It breaks more easily than unwired
glass of the same thickness, but the wire restrains the
fragments from falling out of the frame when broken.
The time during which a curing sealant (usually two
compounds) remains suitable for use after being mixed with a
A board with alternating black and white diagonal lines used
to observe optical transmission and reflection qualities in
coated and uncoated glass.