Industry Terms and References

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Acoustics: The science of sound and sound control.
Adhesion: The property of a coating or sealant to bond to the surface to which it is applied. As an example, Wolverine Glass Products offers “glass bonding” which utilizes a clear adhesive to bond glass together. See Fabrication Capabilities.
Adhesive failure: Loss of bond of a coating or sealant from the surface to which it was applied.
Air side: The side of float glass that was up or exposed to the “air” when it was manufactured, rather than the tin side. The bottom side is referred to as the “tin” side because it floated on a liquid tin bath. Coatings are applied to the air side because it is the “cleanest” side of the glass. The silvering process of making mirror utilizes the “air side” as well.
Air spacer: A desiccant filled frame used to separate two or more lites of glass in an insulated glass unit. The “air space” is the gap between the lites of glass. For example, a standard 1” overall IGU is configured using two (2) lites of ¼” (6 mm) glass with a ½” (12 mm) air space. See Spacer defined.
Annealing: 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.
Argon gas: Argon is an invisible, non-toxic gas used to enhance the energy efficiency and general performance (U-value) of the insulating glass used in windows and doors.
Aspect ratio: The quotient of the long side of a glazing lite over the short side of that lite.
ASTM (American Society for Testing and Materials): A society of engineers which sets standards for testing of materials. www.astm.org
Autoclave: A vessel that employs high-pressure and heat. In the glass industry, autoclaves are used to produce a permanent bond between glass and approved interlayers, creating a laminated glass product. EVA and Resins are other methods of creating laminated glass that do not require an autoclave but may require a different “curing” process.

Backer rod: 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 finished bead.
Back-painted glass: Back-painted glass is produced using a glass substrate, typically clear or low-iron glass, with a water-based or ceramic frit paint applied to the #2 two surface of the glass. See Back-Painted Glass product page.
Beveling: Beveling or beveled glass is made using fabrication equipment that creates an angled “beveled” surface cut around the perimeter of the glass or mirror lite. Beveling is commonly used to enhance mirrors, or glass tabletops, shelving, or counter tops for a more luxurious design. See Edgework under Fabrication Capabilities.
Bite: The dimension by which the framing system overlaps the edge of the glazing infill.
Block: 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 tubes.”)
An insulating glass unit with a tube and/or hole factory-placed into the unit’s 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.
Building envelope: The building envelope is the physical barrier between the exterior and interior environments enclosing a structure. Some may refer to this as the building facade.

CNC machines: The word “CNC” stands for Computer Numerical Control, but today everyone calls it CNC. CNC equipment is used to fabricate glass creating finished products to be used in numerous applications. All automated motion control machines have three primary components – a command function, a drive/motion system, and feedback system. CNC “machining” or “fabrication” is the process of using a computer-driven machine tool to produce a part out of solid material in a different shape.
Capillary tube units: (See also breather tube units)
An insulating glass unit with an exceedingly small inside diameter metal tube of specific length factory-placed into the unit’s 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.
Caulk: (v) The application of a sealant to a joint, crack or crevice; (n) A compound used for sealing that has minimum joint movement capability; sometimes called low performance sealant.
Channel glazing: 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.
Channel width: The distance between opposing glazing stops.
Chamfer: A chamfer is a transitional edge between two faces of an object. Sometimes defined as a form of bevel, it is often created at a 45° angle between two adjoining right-angled faces. See Beveling defined.
Chemically strengthened glass: Glass that has been strengthened by ion-exchange to produce a compressive stress layer at the treated surface.
Compatibility: 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.
Compound: A chemical formulation of ingredients used to produce a caulking, elastomeric joint sealant, etc.
Compression gasket: A gasket designed to function under compression. Example a compression glazed all glass wall or door versus a “wet set” cement type material used to attach door rails, glass handrails and handrail base.
Compression set: The permanent deformation of a material after removal of the compressive stress.
Condensation: The appearance of moisture (water vapor) on the surface of an object caused by warm moist air in contact with a colder object.
Consistency: 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.
Crush: A lightly pitted area on glass resulting in a dull gray appearance.
Curtain wall: A curtain wall is defined as thin, usually aluminum-framed wall, containing in-fills of glass, or metal panels. These walls are not structural. They are designed to carry their own weight, while transferring the load of wind and gravity to the structure of the building. The design makes it air and water resistant, to ensure that the interior of the building remains airtight.
Cutting: 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 load.
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 load.
Design pressure: Specified pressure a product is designed to withstand.
Diffusing: Scattering, dispersing, as the tendency to eliminate a direct beam of light.
Digs: Deep, short scratches.
Distortion: Alteration of viewed images caused by variations in glass flatness or inhomogeneous portions within the glass. An inherent characteristic of heat-treated glass.
Double glazing: (Also referred to as Dual Insulating 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 lites is thoroughly dried and the space is sealed to eliminate possible condensation and to provide superior insulating properties.
Double strength: (DSB, as some still refer to it) In float glass, approximately 1/8 inch (3 mm) thick.
Dry glazing: 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.
Dry seal: 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.
Durometer: The measurement of hardness in an elastomeric material.

EPDM: Ethylene Propylene Diene Monomer, a synthetic rubber.
Edge clearance: Nominal spacing between the edge of the glass product and the bottom of the glazing pocket (channel).
Edge deletion: This is the process of removing the glass coating from the surface of the glass.
Edging: Grinding the edge of flat glass to a desired shape or finish.
Elastomer: An elastic, rubber-like substance, such as natural or synthetic rubber.
Elastomeric: (adj) Having the property of returning to its original shape and position after removal of load. (n) An elastic rubber like substance.
Emissivity: The measure of a surface’s ability to emit long-wave infrared radiation. Common glass type used for energy-efficient glazing is low-emissivity glass, or low-e.
Etched Glass: Etched, or satin etched glass has one or both surfaces of the glass substrate is altered with hydrofluoric acid or other caustic agents. Permanent etching of glass may occur from alkali and other runoff from surrounding building materials. See Satin Etched Glass product page.
Exterior glazed: Glazing infills set from the exterior of the building.
Exterior stop: The molding or bead that holds the lite or panel in place when it is on the exterior side of the lite or panel.

Facade: 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, or the building envelope.
Face glazing: 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 pocketed sash.
Fade factor: The measure of the ability of a glass type to reduce fading or damage to interior fabrics and materials. The ISO Damage Weighted Transmittance (Tdw-ISO) calculation assigns a specific damage weighted factor to each wavelength of UV or visible light (from 300nm to 680nm), based on its contribution to fading. Tdw-ISO is expressed as a number between 0 and 1. The lower the value, the lower the risk of fading to interior fabrics and materials.
Fenestration: Any glazed panel, window, door, curtain wall or skylight unit on the exterior of a building.
Figured glass: (See “patterned glass”)
Fillet bead: Caulking or sealant placed in such a manner that it forms an angle between the materials being caulked.
Flare: A protrusion on the edge of a lite of glass.
Flat glass: A general term that describes float glass, sheet glass, plate glass and rolled glass.
Float 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. The float glass process yields a flatter, higher quality of architectural glass than previous methods common prior to the 1960s. Click here to see how float glass is produced.
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.
Fogging: A deposit of contamination left on the inside surface of the sealed insulating glass unit due to extremes of temperatures. This typically occurs as a result of the insulating glass unit “seal” failing. This does NOT mean, however, that the seal failure resulted from a manufacturing defect. Improper installation, external contaminants, or settling of the construction can contribute to seal failures. (See Condensation)
Fourth surface low-e: This refers to an insulated glass unit that has a pyrolytic (hard-coat) low-e coating on the #4 surface of an insulating glass unit. Typically, there will be a sputter (soft coat) low-e coating on the #2 surface. Hence, two coatings utilized within one insulating glass unit.

Gas-filled units: Insulating glass units with a gas other than air in the air space to decrease the unit’s thermal conductivity (U-factor) or to increase the unit’s sound insulating value.
Gaskets: 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.
Glass: A hard and somewhat brittle solid surface material that is typically transparent or translucent. It is made by fusing silicates, under extremely high temperatures, with soda, lime, sand, and other components. Glass can be further processed to create high performing and/or decorative solutions for a variety of interior and exterior design applications.
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 process.
Glass fines: 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 based on end use and allowable blemishes. It is customary that glass is allowed to have allowed blemishes based on size of blemish, distance viewed, angle viewed and lighting.
Glass surface designations: When referring to different glass coatings or processes, it is common to refer to the glass surface on which the coating is applied. For example, a monolithic lite of glass has two (2) surfaces. A dual insulating glass units has four (4), a triple IGU has six (6) and so on. See Vitro Architectural Glazing diagram below as an example of standard designations.

Glazing: (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.
Glazing bead: A strip surrounding the edge of the glass in a window or door, which holds the glass in place.
Glazing channel: A three-sided, U-shaped sash detail into which a glass product is installed and retained.
Gun consistency: Sealant formulated in a degree of viscosity suitable for application through the nozzle of a caulking gun.

Heat-absorbing glass: Glass that absorbs an appreciable amount of solar energy.
Heat-resisting glass: Glass able to withstand high thermal shock, generally because of a low coefficient of expansion.
Heat soaking: Heat soaking is a process that may expose nickel sulfide inclusions (NiS) in tempered glass. The process involves placing the tempered glass inside a chamber and raising the temperature to approximately 550°F or 287° to accelerate NiS expansion. This causes glass containing NiS inclusions to break in the heat soak chamber, thus reducing the risk of potential field breakage. The heat-soaking process is not 100 percent effective. In addition, heat-soaking creates higher costs and carries the risk of reducing the compressive stress in tempered glass.
Heat-strengthened glass: Flat or bent glass that has been heat-treated to a specific surface and/or edge compression range to meet the requirements of ASTM C 1048, Kind HS. Heat-strengthened glass is approximately two times as strong as annealed glass of the same thickness when exposed to uniform static pressure loads. Heat-strengthened glass is NOT considered safety glass and should not be used in hazardous location such as doors, sidelites or other at-risk applications.
Heat-treated: Term used for both fully tempered glass and heat-strengthened glass.
Heel bead: 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.
High-transmission glass: Glass, which transmits an exceptionally high percentage of visible light.

IBC (International Building Code): The International Building Code (IBC) is the foundation of the complete Family of International Codes®. It is an essential tool to preserve public health and safety that provides safeguards from hazards associated with the built environment. It addresses design and installation of innovative materials that meet or exceed public health and safety goals. Visit International Code Council to learn more.
IGCC (International Glass Certification Council): The IGCC certification program is predicated on the concept of independent and impartial administration of periodic accelerated laboratory testing and unannounced plant inspections to assure continuing quality product performance. www.igcc.org
Inclusion: Presence of foreign matter in a finished material, such as glass.
Insulating glass unit: Two or more lites of glass spaced apart and hermetically sealed to form a single-glazed unit with a space between the lites. (Commonly called IG units or IGU)
Interior glazed: Glazing infills set from the interior of the building.
Interior stop: The removable molding or bead that holds the lite in place when it is on the interior side of the lite.
Interlayer: Any material used to bond two lites of glass and/or plastic together to form a laminate. (See laminated glass)

Jambs: The vertical frame members at the perimeter of the opening.

Laminated glass: A type of safety glass is held in place by an interlayer, typically of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. Laminated glass can be produced using polycarbonates (PET) as well.
Laminated plastics (plastic laminates): Two or more lites (or sheets) of polycarbonate (or acrylic) with a compatible interlayer between the plastic sheets of polycarbonate or acrylic bonded together under heat and pressure.
Lehr: A long, tunnel-shaped oven for annealing glass, usually by a continuous process.
Lite: 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”.
Live load: 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.
Light-to-solar gain ratio: The ratio of visible light transmission (VLT) to solar heat gain of a glazing system divided by the solar heat gain coefficient: LSG = VLT ÷ SHGC. 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. Glass with higher LSG numbers is typically desired by architects because they offer superior solar control, with relatively high visible light transmittance.

Mastic: Descriptive of heavy-consistency compounds that may remain adhesive and pliable with age. Mastic, also referred to as “mirror” mastic as this is a common method of installing mirror on a wall. We do, however, recommend that mechanical fasteners are used when installing mirrored walls to ensure proper safety.
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.
Migration: (See bleeding)
Spreading or creeping of a constituent of a compound onto/into adjacent surfaces. See bleeding.
Mirror: Mirror is produced using a clear, low-iron, tinted or satin etched glass substrate with a layer of silver, copper and protective paint backing applied to the #2 surface. If laminated, the interlayer and clear glass lite should be laminated to the #1 (face) surface of the mirror—NOT to the paint side. Tempered mirror is available, but the glass must be tempered before the mirroring process occurs. For safety glazing applications, it is more common to use a safety tape backing applied to the painted surface since tempered mirror can be expensive and the heat-treating process may create distortion. For satin etched mirror, the etched surface will be the #1 (face) surface.
Modulus: Stress at a given strain. Also, tensile strength at a given elongation.
Mock-up: A model of a section of a wall or its parts, built to scale or at full size, for purposes of studying its construction details, judging its appearance, and/or testing its performance. Architects may require a mock-up before approving a product to be specified to fully evaluate the aesthetics or other characteristics of the “finished” product.
Mullion: A horizontal or vertical member that supports and holds such items as panels, glass, sash, or sections of a curtain wall.
Multiple-glazed units: Insulating glass units with three or more lites of glass.
Muntins: Horizontal or vertical bars that divide the sash frame into smaller lites of glass. Muntins are smaller in dimensions and weight than mullions.

Neoprene: A synthetic rubber having physical properties closely resembling those of natural rubber. It is made by polymerizing chloroprene, and the latter is produced from acetylene and hydrogen chloride.
Non-drying (non-curing): A sealant that does not set up or cure.
Non-sag: 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.
Non-skinning: Descriptive of a product that does not form a surface skin.
Non-staining: Characteristic of a compound, which will not stain a surface.
Nozzle: The tubular tip of a caulking gun through which the compound is extruded.
OITC (outside-inside transmission class) – 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: Glass that is made translucent or opaque. Patterned glass and satin-etched glass are examples.
Opacified glass: Glass with ceramic frit or a silicone-based paint applied to one surface to make it opaque. A common use is spandrel glass which is designed for non-vision areas of a building to hide mechanical systems, floor slabs and columns. See Spandrel Glass product page.
Organic: Any compound which consists of carbon and hydrogen with a restricted number of other elements, such as oxygen, nitrogen, sulphur, phosphorous, chlorine, etc.

Passive solar control: Passive solar control glass is designed to transmit the warming rays of the sun, creating greater energy efficiency and interior comfort for heating-dominated climates because it improves thermal performance and reduces solar heat gain. Ideal for colder climate zones. Pyrolytic (hard-coat) low-e glass is a passive solar glass.
Patterned glass: 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. See Patterned Glass product page.
Permanent set: The amount by which a material fails to return to its original dimensions after being deformed by an applied force or load.
Pocket (channel): A three-sided, U-shaped opening in a sash or frame to receive glazing infill. Contrasted to a pocket, 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 (channel) width: The measurement between stationary stops (or stationary stop and removable stop) in a U-shaped channel.
Point supported glass: Glass attached to the building structure using bolted fittings directly connected through finished holes in the glass. Some refer to this hardware as “spider fittings”.
Polariscope: A device for examining the degree of strain in a sample of glass.
Polished wired glass: Wired glass that has been ground and polished on both surfaces. See wired glass defined. Note that wired glass is NOT a safety glazing product and should not be used in doors, sidelites, or other hazardous locations. In addition, while technically wired glass has some fire-protection capability the maximum size and applications are restrictive. See Fire-Rated Glass product page.
Polyisobutylene: Typically the primary seal in a dual seal IG unit and the key component in restricting moisture vapor transmission.
Polymer: A chemical structure consisting of long chains of molecular units.
Polysulfide sealant: 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.
Polyurethane sealant: An organic compound formed by the reaction of a glycol with an isocyanate.
Polyvinyl chloride (PVC): Polymer formed by polymerization of vinyl chloride monomer. Sometimes called vinyl.
Pre-shimmed tape sealant: A sealant having a pre-formed shape containing solids or discrete particles that limit its deformation under compression.
Primer: 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.
Priming: 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.
Protective glazing: Protective glazing commonly refers to products that have been tested and approved for the purpose of delaying or preventing forced entry, such as hurricane impact, bullet or blast resistant glass or polycarbonates. For example, while tempered glass is a safety glazing material. It should not be used in a protective glazing application.
Prototypes: A prototype is an early sample, model, or release of a product built to test a concept or process. A prototype is generally used to evaluate a new design to enhance precision by system analysts and users. Wolverine Glass Products is pleased to work with manufacturers through the early design and engineering process when glass may be used as a component part of a finished product.
Pyrolytic deposition: A process for applying a thin metallic coating to the surface of flat glass during the float glass manufacturing process. A “pyrolytic” coating is commonly referred to as a “hard coat” or “hard coated glass”. Pyrolytic coated glass does not require edge-deletion, or other special handling and typically has no shelf life, unlike sputter coated glass (soft coated glass). Low-emissivity glass is available with pyrolytic or sputter coatings with varying levels of performance.

Quench: Also referred to as the “quenching process” means to rapidly cool which occurs when glass is heat-treated.

Rabbet: An “L” shaped section, which can be face glazed or receive a removable glazing bead to hold the lite of glass in place.
Racking: A movement or distortion of sash or frames causing a change in angularity of corners.
Reflectance: Light reflectance is expressed as a % of reflectivity from the glass surface that is in a given spectrum range; Visible Out covers the reflectance on the exterior surface (surface 1 facing the elements) in the visible spectrum from 380 nanometers to 780 nanometers, Visible In covers the reflectance of the interior surface (facing the inside of the living space) in the visible spectrum from 380 nanometers to 780 nanometers and Total Solar Energy Out covers the reflectance of the exterior surface (surface 1 facing the elements) in the ultraviolet, visible and near infrared energy from 300 nanometers to 2100 nanometers. Typically, it is best to achieve a lower % of reflectance to the interior and most times for the exterior as well.
Reflective glass: 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-factor). The value is expressed in Btu/hr/ft2 (W/m2). The relative heat gain is calculated as RHG = (Summer U-factor x 14 of) + (Shading Coefficient x 200). The lower the relative heat gain, the more the glass product restricts heat gain.
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: Also referred to as “roll-wave distortion” due to the 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 reflection.
Roll impressions: 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-inch-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.
Rolled glass: Glass formed by rolling, including patterned and wired glass.
Rough opening: The opening in a wall into which a door or window is to be installed.
Rub: A series of small scratches in glass generally caused during transport by a chip lodged between two lites.
R-value: The thermal resistance of a glazing system expressed ft2/hr/of/Btu (m2/W/oc). The R-value is the reciprocal of the U-factor. The higher the R-value, the less heat is transmitted throughout the glazing material.

Sash: The window frame, including muntin bars if used, to receive the glazing infill.
Score: 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 shape.
Scratches: 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.
Sealant: 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”)
Seam (verb): To grind, usually with an abrasive belt, wet or dry, the sharp edges of a piece of glass.
Seeds: Minute bubbles in float glass less than 1/32 inch (0.79375 mm) in diameter.
Setting: Placement of lites or panels in sash or frames. Also, action of a compound as it becomes firmer after application.
Setting blocks: 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.
SGCC (Safety Glazing Certification Council): A non-profit corporation that provides for the certification of safety glazing materials.
Shading coefficient: The ratio of the solar heat gain through a specific glass product to the solar heat gain through a lite of 1/8 inch (3mm) clear glass. Glass of 1/8 inch (3mm) thickness is given a value of 1.0; therefore, the shading coefficient of a glass product is calculated as follows:
Shading Coefficient = Solar Heat Gain of the Glass ÷ Solar Heat Gain of 1/8″ Clear Glass
Shadowgraph: A device for inspecting glass with respect to distortion and other defects.
Sheet glass: Flat glass formed by vertically drawing a ribbon of glass from a container of hot glass. Sheet glass has been almost completely replaced by float glass. See Float Glass defined.
Shelf life: 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.
Shore “a” hardness: Measure of firmness of a compound by means of a Durometer Hardness Gauge (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).
Sight line: 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 finished off.
Silicone sealant: A sealant having as its chemical composition a backbone consisting of alternating silicon-oxygen atoms.
Sloped glazing: Any installation of glass that is at a slope of 15 degrees or more from vertical.
Smoke: Streaked areas appearing as slight discoloration on glass.
Smoke baffle: Smoke baffles are designed to contain smoke during a building fire and prevent the smoke from spreading to other areas. These are typically installed in a ceiling area and extend vertically, hence many times referred to as a smoke curtain. Make sure to check with local jurisdiction to ensure code requirements are met regarding glazing and other materials used.
Solar control glass: Tinted and/or coated glass that reduces the amount of solar heat gain transmitted through a glazed product. Solar control glass is ideal for warm to hot climate zones that make it especially important to achieve a lower solar heat gain coefficient (SHGC) to meet the code requirements. See Pyrolytic coatings and Sputter coatings used to product low-e glass.
Solar energy reflectance: (See reflective glass)
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 (SHGC): 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.
Solarization: Change in transmission, and sometimes color, of plastics because of exposure to sunlight or other radiation.
Sound transmission class (STC): 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 materials. Laminated glass is ideal for reducing sound transmission. STC ratings will vary based on the thickness of the glass, the interlayer, or configuration of the monolithic or insulating glass panel. See Laminated Glass product page.
Sound transmission loss (STL): 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. This measurement is expressed in decibels (db). Also called “Transmission Loss (TL).”
Spacers (shims): 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. See Insulating Glass product page for spacer types used.
Spandrel: The panel(s) of a wall located between vision areas of windows, which conceal structural columns, floors, and shear walls—hence the reference to Spandrel Glass. See Opacification glass defined. See Spandrel Glass product page.
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) deposition)
Process for applying multiple layers of metallic coatings to the surface of flat glass in a vacuum chamber. Sputter coated low-e glass is commonly referred to as a “soft coat” or “soft-coated glass”, which must be edge-deleted during the fabrication process of an insulating glass unit and soft coats do have a shelf life. Sputter coated low-e glass is typically more expensive than pyrolytic coatings but yields higher performance levels when it comes to energy-efficient glazing.
Stain: 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.
Stones: Any crystalline inclusion imbedded in the glass.
Stop: Either the stationary lip or the removable molding of the pocket, serving to hold the glazing infill in the sash or frame, with the help of spacers.
Storefront: A storefront is defined as a non-residential, non-load-bearing assembly of commercial entrance systems and windows, usually spanning between the floor and the structure above.
Storm door: A panel or sash door placed on the outside of an existing door to provide additional protection from the elements.
Storm window: A glazed panel or sash placed on the inside or outside of an existing sash or window as additional protection against the elements.
Strain: The percentage of elongation or compression of a material or portion of a material caused by an applied force.
Strain pattern: 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 glass.
Stress (residual): Any condition of tension or compression existing within the glass, particularly due to incomplete annealing, temperature gradient, or inhomogeneity.
Striking off: 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 lock strip 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.
Substrate: A base material to which other materials or fabrication procedures are applied.
Summer Day U-value: The calculation of U-Value using Summer Daytime environmental conditions of a hot outside temperature and direct sunlight.
Surface compression: Compressive stresses at and beneath the surfaces of heat-treated glass and balanced by the CENTER TENSION stresses.

Tape sealant: A sealant having a pre-formed shape and intended to be used in a joint under compression.
Tempered glass: Commonly referred to as “fully tempered glass” – Flat or bent glass that has been heat-treated to a high surface and/or edge compression to meet the requirements of ASTM C 1048, Kind FT. Fully tempered glass, if broken, will fracture into many small pieces (dice). Fully tempered glass is approximately four times stronger than annealed glass of the same thickness when exposed to uniform static pressure loads. Outside of North America, sometimes called “toughened glass.”
Thermal break: An element of low conductivity placed between elements of higher conductivity to reduce the flow of heat and cold, i.e., insulation.
Thermal endurance: The relative ability of glass to withstand thermal shock.
Tin side: The bottom side of float glass as it was manufactured. Called “tin side” because the glass “floats” on a bath of liquid tin while it is being produced. See Float Glass defined.
Tinted glass: 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.
Toe bead: 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.
Tong marks: 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.
Tooling: 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 the surface of a sealant in a joint so that it is flush with the surface.
Toughened glass: International terminology for fully tempered glass. (See “fully tempered glass”.)
Transmittance: The ability of the glass to pass light and/or heat, usually expressed in percentages (visible transmittance, thermal transmittance, etc.).
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.

Ultraviolet: The name of the invisible portion of the light spectrum with wavelengths shorter than 390 nanometers.
Unit (or IGU): Term normally used to refer to one single assembly of insulating glass, no matter if dual or triple glazed.
United inches: Total of one width and one height of a lite of glass in inches.
U-value (U-factor): A measure of the insulating characteristics of the glass or how much heat gain or loss occurs through the glass due to the difference between indoor and outdoor temperatures. The lower the number, the better the insulating performance. This number is the reciprocal of the 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”)
Vinyl glazing: Holding glass in place with extruded vinyl channel or roll-in type.
Visible light reflectance: The percentage of visible light (390 to 770 nanometers) within the solar spectrum that is reflected from the glass surface.
Visible light transmittance: The percentage of visible light (390 to 770 nanometers) within the solar spectrum that is transmitted through glass.

Warm edge technology: Warm edge technology or warm-edge spacers refer to the edge construction of a double or triple glazed insulating glass unit that conducts less heat or cold than traditional windows and standard construction glazed units. Standard IGU’s are constructed with an aluminum “box” spacer to hold the glass apart. Wolverine Glass Products offers a variety of spacer types, including Premium Super Spacer® warm-edge spacers to meet the highest standards for energy-efficiency.
Wave: 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.
Weather-stripping: 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.
Wet seal: Application of an elastomeric sealant between the glass and sash to form a weather-tight seal.
Window: 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.
Winter Night U-value: The calculation of U-Value using Winter Nighttime environmental conditions of a cold outside temperature and no sunlight.
Wired glass: 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. Wired glass can be used in limited applications and sizes for fire-protection. 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. Wired glass is NOT a safety glazing solution and should NOT be used in doors, sidelites or other hazardous locations.
Work life: The time during which a curing sealant (usually two compounds) remains suitable for use after being mixed with a catalyst.

Zebra board: A board with alternating black and white diagonal lines used to observe optical transmission and reflection qualities in coated and uncoated glass.

Industry Terms and References

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