Glossary of Auto Glass Industry Terms


Acute Area

The area of the windshield directly in front of the driver's eyes, beginning just above the steering wheel. It measures approximately 8 1/2 inches high by 11 inches wide. This area is used as the standard for the driver's critical vision area by most auto glass shops and insurance companies in the United States.


The clinging or sticking together of two surfaces. The ability of an adhesive to stick to a surface.

Adhesive Failure

Adhesive failure indicated by the material's failing (pulling loose) at the surface of the substrate. Similar to "scotch" tape peeling off a plastic substrate.


Any substance that is capable of bonding other substances together by surface attachment. In an auto glass replacement context, it is a high-strength polyurethane material unless otherwise specified.


A passive restraint system that uses an explosive device to inflate a bag at a high rate of speed. The bag inflates with a gas and then quickly deflates when a vehicle occupant is thrown into it. It is mounted in the steering wheel on the driver's side of the vehicle and in the dashboard on the passenger's side. There are also airbags installed for side impact collisions. Some passenger-side airbags use the windshield to position the deploying bag.


A broad class of organic compounds. In this context they are industrial solvents that include methanol (used in windshield washer fluid), denatured alcohol (used in glass cutting) and isopropyl alcohol (IPA, used as a cleaning solvent).

ANSI Standards

Health and safety standards set by the American National Standards Institute.


An abbreviation of the aftermarket auto glass industry. Automotive Replacement Glass/Aftermarket Glass Replacement.

Auto Glass Repair

The act of repairing a break in a windshield or other laminated auto glass part, rather than replacing it. Auto glass repair is a permanent process that removes the air from the break and fills it with a curable, optically matched resin. Same as windshield repair.


A sealant or adhesive compound after application in a joint, irrespective of the method of application, such as a urethane bead applied to a pinchweld. A bead looks like a ribbon of adhesive rather than a round drop of adhesive.

Block (setting)

A small piece of neoprene or other suitable material used to position the glass in the frame or opening.

Body Fillers

Compounds used to build up and level low areas that cannot be brought back to their original contour by straightening.

Bond Strength

The force, per unit area, necessary to rupture a bond.


The attachment at an interface between substrate and adhesive or sealant.

Bull's Eye

Impact damage to laminated glass that is marked by a clean, separated cone in the outer layer of the glass.


The application of sealant to the surface of substrate before placing another substrate in position.

Butyl Dam

See "Butyl." Butyl Tape Kits have been used as positioning dams. Other terms for a butyl dam are: Sealant Dam, Tape Kit.

Butyl Rubber

A copolymer of isobutene and isoprene. As a sealant, it has low recovery and slow cure, but good tensile strength and elongation.


An adhesive used in earlier model vehicles for glass retention. It is a petroleum product that requires no curing or hardening. Butyl is available in rolls of approximately 15 feet. Sometimes called "Butyl Tape Kit" or "Tape Kit." It is available in various thicknesses and shapes.

Cap Bead

A finished bead applied at the top of an installation.


The substance added in small quantities to promote a reaction, while remaining unchanged itself.

Caulk (noun)

A sealant with a relatively low movement capability.

Caulk (verb)

To fill the joints with a sealant.


A resilient mastic compound often having a silicone, bituminous, or rubber base; used to seal cracks, fill joints, prevent leakage, and/or provide waterproofing.

Channel Tape

A cork and rubber composition material used to secure door glass and to fill channels.


A piece of U-shaped metal lined with felt used to reduce glass breakage and noise, and to correct alignment of moveable glass parts.

Chemical Cure

Curing by chemical reaction. This usually involves the cross-linking of a polymer.

Close-Cut Or Partial-Cut Installation

An installation method that leaves most of the existing adhesive bead/bed adhered to the metal frame and adds a small fresh bead of adhesive into which to set the glass. Some vehicle manufacturers do not recommend this procedure.

Coated Glass

Glass with a chemical film applied to one surface. The film can provide such enhanced performance characteristics as privacy, solar or mirror effects.


The ability of a sealant or adhesive to hold itself together. The internal strength of an adhesive or sealant.

Cohesive Failure

Adhesive failure indicated by hardened material on both substrate surfaces. The material itself failed (the body of the adhesive or sealant pulled apart).

Combination Break

A break in a windshield involving more than two types of breaks.


Refers to the reaction a sealant has on another sealant or on another material.

Compression Gasket

A system that uses a soft gasket on one side of the glass and a firm, dense gasket called a wedge on the other.

Compression Set

Occurs when a sealant is crushed and does not return to its original dimension when the load is removed.


A substance, liquid or solid, which is present in a break. Contaminants must be removed from a break before a repair can begin.


The chemical reaction of air, moisture, or corrosive materials on a surface; also called oxidation. The process of wearing away the surface of a solid.

Cosmetic Blemish

A defect in the appearance of a vehicle. Includes torn upholstery, scratched paint and resin spills.


An extended crack in a windshield from both sides of an impact point. There are several different kinds of cracks: Short crack: A crack on the windshield of 6 inches (15.24 cm) or less. Long crack: A crack on the windshield of more than 6 inches (15.24 cm).Edge crack: Any crack on the windshield that extends to an edge. Floating crack: Any crack on the windshield that does not extend to an edge. Stress crack: Any crack extending from an edge without an impact point.


A phenomena that occurs to plastic when it is exposed to either harsh weatherization, U.V. light or force bending beyond the recommended minimum radius.


Molecules that are joined side by side as well as end to end.

Cure Time

The time required for a chemical or material to dry or set at a given temperature and humidity. Cure time varies with the type of material used and the thickness of the application.

Curing Agent

A chemical which is added to effect a cure in a polymer.


A process of drying and hardening over a given period.


A device having a two-fold purpose:  1. A dam cushions and separates the glass from the metal frame where the glass adheres. 2. A dam holds the liquid adhesive and prevents it from flowing into the interior of the vehicle.


Same as break and crack.


The failure of the bond between layers, as when windshield glass separates from the laminate, or when paint peels from the substrate beneath it.


A term often used by the public to refer to a stone damage to a windshield.

Double Seal Units

Insulating glass with two materials used to form the seal of the glass.

Dry Glazing

A method of securing glass in a frame by use of a dry, preformed, resilient gasket without the use of a compound.


A blunt probe used to penetrate sealants that measures the hardness from 0 to 100.

Edge Crack

Any crack on the windshield that that extends to an edge. See also: Crack. Up to 90% of all edge cracks are the result of road debris striking the outer perimeter (2"-3") of the windshield where stresses from the windshield manufacturing and installation processes are greatest. Although undesirable, the crack forms to relieve the stresses.


A measure of how well a sealant "bounces back" after it has been stretched.


A rubbery material which returns to approximately its original dimensions in a short time after a relatively large amount of deformation.


A property of urethane adhesive: An increase in length expressed numerically as a fraction or percentage of initial length.


The ability of a sealant to stretch under tensile load.

Extrusion Failure

The failure that occurs when a sealant is forced too far out of the joint.

Fast Cure Urethane

A faster hardening adhesive. The term "fast" is relative to the surrounding temperature and humidity. Curing time is faster than for normal adhesives.

Fatigue Failure

The failure of a material due to rapid cyclic deformation.

Federal Motor Vehicle Safety Standards (FMVSS)

A series of standards required of the automobile manufacturers by the Federal Government. All new vehicle models must meet these standards before they are allowed to be sold in the United States.

Filler Strip

A strip inserted into a rubber gasket after the glass is installed, forcing the gasket against the glass to form a seal and improve the grip. It is sometimes called locking a bead or spline.


Finely ground material added to a sealant or adhesive to change or improve certain properties.

Floating Crack

Any crack on the windshield that does not extend to an edge. See also: Crack.


A flower petal effect around the outer edge of a repair. This is caused by the laminate detaching from the outer layer of glass.


The painted band around the perimeter of auto glass parts.

Full Strip Installation

An installation method whereby the technician removes the existing bed/bead of adhesive from the vehicle frame. Approximately 1-2 mm of old adhesive remains. The technician applies new/fresh adhesive on top, then sets the glass into the fresh adhesive.


A seal, usually of rubber, that holds a piece of auto glass to the vehicle body. There are various sizes and shapes of glass part gaskets, depending on vehicle design.

Glazing Compounds

A soft dough-like material used for filling and sealing the space between a pane of glass and its surrounding frame.


The work of installing glass in a frame.

Green Strength

A term used by some adhesive manufacturers to describe initial strength of an adhesive.

Gun-Grade (gunnable sealant)

Sealant that is meant to be applied with a caulking gun.

Half Moon

Damage to a windshield that has a half-circle separation around the impact point. It is similar to a bull's eye.

Heated Urethane

A type of adhesive that is heated to a prescribed temperature before application. The heat "pre-cures" the adhesive for faster release of the vehicle.

Hot Melt Butyl

An insulating glass edge sealant used during manufacturing.

Impact Resistance

The measurement by which it is determined how much impact is required for breakage.

Impact Site

The actual location on the outside layer of glass, where it was struck by an object (usually a stone). Typically a small piece of glass is missing.


This is the most common break. It occurs when an object hits the windshield.

Laminated Glass

A type of safety glass that has a layer of plastic bonded between layers of glass. Laminated glass is used mainly for windshields.


Vinyl inner layer of laminated glass.


Short cracks that emanate from a break.

Light Transmittance

The percentage of visible light able to pass through.

Long Crack

A crack on the windshield of more than 6 inches (15.24 cm). See also: Crack.

Mastic (broad interpretation)

Any field molded sealant or adhesive. Includes materials which are gunned, poured or troweled into place.

Mobile Unit

A vehicle, usually a van or light truck, properly equipped with repair and safety equipment and tools, driven to an auto glass repair customer's home or place of business. Glass repairs are made from the vehicle.


The ratio of stress to strain.


A material composed of single molecules. A building block in the manufacture of polymers.


Material Safety Data Sheets, required for all toxic or hazardous materials used by a company.


A synthetic rubber having physical properties closely resembling those of natural rubber but not requiring sulphur for vulcanization.  Extremely good weather resistance (both heat and cold) with ultraviolet stability.


Abbreviation for "original equipment manufacturer."

One-Part Sealants

Sealants that require no premixing.

One-Part Urethane

An adhesive used in auto glass replacement that has only one component.

Open Time

The time interval between the application of an adhesive and when it becomes no longer workable.


Formation of an oxide. Also the deterioration of rubbery materials due to the action of oxygen or ozone.

Peel Test

A test of an adhesive or sealant using one rigid and one flexible substrate. The flexible material is folded back (usually 180 degrees) and the substrates are peeled apart. Strength is measured in pounds per inch of width.

Permanent Set

Occurs when a sealant is stretched, released, and does not return to its original length, but remains longer.

PIB tape

Poly-Isobutylene Tape; used to form the primary seal of a dual seal insulating glass unit.


The impact point from which, typically, a small piece of glass is missing.


A material that softens a sealant or adhesive by solvent action.


The centigrams (cgs) unit of viscosity.

Poly Vinyl Butyral

Vinyl inner layer of laminated glass.


A compound consisting of long chain-like molecules. The building units in the chain are monomers.

Polysulfide Rubber

A synthetic polymer usually obtained from sodium polysulfide. Polysulfide rubbers make very good sealants.

Polysulfide Sealants

Sealants that adhere well to glass, aluminum, and spacer and corner materials.


An adhesive used to bond auto glass to vehicles prior to the advent of urethane.

Polyvinyl Butyral (PVB)

A plastic film used in laminated glass.


A cleaner or a product that enhances an adhesive. A prep is usually applied to the glass prior to the primer.

Pressure Sensitive Adhesive

Adhesive which retains tack after release of the solvent, so that it can be bonded by simple hand pressure.


An undercoat or chemical applied to a surface to improve the adhesion, durability, and appearance of a topcoat or the bond of an adhesive. A product (chemical) used to prepare metal bonding areas and ensure a strong bond between the glass part and the adhesive.

Primerless Urethane

A type of urethane adhesive that requires no primer on the glass surface. Metal primers may be necessary.

Pump Gun

A device used for pumping sealants and adhesives.


See "polyvinyl butyral".

Release Agent

A liquid solvent used to soften adhesives or sealants.


A measure of energy stored and recovered during a loading cycle. It is expressed in percentage.


A solid organic material, generally not soluble in water, which has little or no tendency to crystallize. Resin is optically matched to auto glass, and is used to fill breaks and cracks.

Reveal Molding

Chrome or plastic molding which fits over and covers the edges of the windshield and back glass.

Rubber Blocks or Spacers

Small rubber blocks/spacers, used by some manufacturers, to separate the glass from the metal frame.

Safety Glass

A general term used for either laminated or tempered glass. Only glass which has been laminated, however, can specifically be called laminated safety glass.

Safety Glazing

See "tempered glass".


Any material used to seal joints or openings against the intrusion or passage of any foreign substance, such as water, gases, air or dirt.


A surface coating generally applied to fill cracks, pores or voids in a surface.

Shaded Glass

Laminated glass in which a dark color has been added to the top section of the inner vinyl layer to improve driver visibility in glare. The color typically becomes lighter as the tint travels down the glass.

Shear Test

A method of deforming a sealed or bonded joint by forcing the substrates to slide over each other. Shear strength is reported in units of force per unit area (psi).

Shelf Life

The amount of time the adhesive material stays fresh without being used. If the material exceeds its shelf life, some of the adhesive properties may be lost.

Shore Hardness

The measure of firmness of a compound by means of a Durometer Hardness Gauge. (Range of 20-25 is about the firmness of an art gum eraser. Range of 90 is about the firmness of a rubber shoe heel.)

Short Crack

A crack on the windshield of 6 inches (15.24 cm) or less. See also: Crack.


The percentage weight loss under specified conditions.


Passenger car side windows.


A chemical used as a lubricant or as a sealant with a wide variety of usage.

Skinned Over

The appearance of an adhesive when it has started to cure.

Spacers, Flat

Small blocks of composition, neoprene, etc., placed on each side of lites to center the lites in the channel and maintain uniform width of sealant beads. They prevent excessive sealant distortion.


A term used to denote filler strips.

Star Break

Damage to a windshield marked by various-sized cracks radiating from the central impact point.

Static Mixer

A tube-like nozzle with a uniquely shaped insert that mixes two adhesive component materials together before the adhesive is dispensed.

Stone Break

A break on the outer layer of a laminated windshield. Typical stone breaks are star breaks, bullseyes or combination breaks.

Stress Cracks

Cracks resulting from unusual forces acting on the glass body.


A hard surface, such as glass or metal, to which a sealant or adhesive is bonded. It is used to test adhesive product strengths.

Tack, Tackiness

The stickiness of the surface of a sealant or adhesive.

Tape Glazing

Installing glass or products with butyl tape.

Tear Strength

The load required to tear apart a sealant specimen.

Tempered Glass

A strong, break-resistant type of safety glass that, if broken, shatters into small granular pieces.


Strengthening glass with heat.

Tensile Strength

Resistance of a material to a tensile force (a stretch). The cohesive strength of a material, expressed in pounds per square inch (psi).


The act of straining or stretching.

Thermal Movement

Movement and changes in a structure caused by temperature changes.

Thermal Stress

As glass heats, it expands.  The center portion of a lite gets hotter and expands at a greater rate than the edges. When this occurs it strains the edges.  This is called thermal stress.

Tinted Glass

Glass to which a small amount of color has been added consistently throughout the glass BATCH. The tinting reduces glare and absorbs heat.


The pressing of a compound in and against the side of a joint to form good adhesion; also dressing of a joint's surface compound for good appearance.


A crack which occurs when the windshield is twisted, either by flexing in the vehicle frame or because of improper mounting. It can be helped along if the windshield has a nick in the edge.

Two-Part Adhesive/Urethane

A type of adhesive that has two component parts: Hardener and resin. In auto glass adhesives, there are two-part urethanes and two-part adhesives. Although they are different chemically, they do have similar performance characteristics.

Ultimate Elongation

Elongation at failure.

Ultra violet (UV) Light

Part of the light spectrum. Ultra violet rays can cause chemical changes in rubbery materials and polymers.

Unibody Construction

A type of automobile construction. The strength of unibody construction does not lie only in the structural frame but rather in the strength of the whole.

Unleaded Frit

A painted band around the perimeter of the glass applied with unleaded paint. It requires special preparation before bonding.

Urethane Breakdown

Results when urethane is exposed to ultra-violet light. Urethane breakdown appears as a chalky black powder on the surface of the hardened adhesive.


A family of polymers ranging from rubbery to brittle. Usually formed by the reaction of a diisocyanate with a hydroxyl; also called polyurethane.

VIN Plate

A permanently installed plate, displaying the vehicle identification number, which is viewable through the windshield from outside the vehicle.


A measure of the flow properties of a liquid or paste.


A process in which rubber is treated with chemicals to harden and strengthen it.

Wedge Glazing

Interior, flexible, continuous, pressure fit gasket that insures a high compression seal between the glass and aluminum, while applying pressure and seal to the outside architectural glazing tape.

Wet Glazing

A method of sealing glass in a frame by use of sealants rather than dry-glazing gaskets.

Windshield Repair

The act of repairing a break in a windshield, or other laminated auto glass part, rather than replacing it. Windshield repair is a permanent process that removes the air from the break and fills it with a curable, optically matched resin. Same as auto glass repair.

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