Glossary (A - K)

Below you will find explanations of some common terms used in the glass and glazing industry.

A B C D E F G H I J K

A

Absorption: That portion of total incident radiation that is absorbed by the glass and subsequently re-radiated either outside or inside.
Abrasion: A wearing, grinding or rubbing away by friction.
Abrasion Resistance: The inherent ability of a coating or substrate to resist degradation or destruction by friction.
Acid Etching: The process of decorating glass, which involves the application of hydrofluoric acid to the glass surface.
Acuity: Sharpness of image.
AFRC: - Australian Fenestration Rating Council - the Australian body which manages the performance ratings of various glass types.
AGGA: - Australian Glass & Glazing Association - has been formed to bring together for the benefit of the Australian Flat Glass Industry, representatives of the main groups in the industry via glass merchants and glaziers, the local glass manufacturers, agents representing overseas glass manufacturers, industry suppliers and any other interested parties. Website: www.agga.org.au
Airspace: The space in the cavity between two glass panes in an insulated glass unit.
Ambient Temperature: The surrounding temperature existing at any given time.
Annealed Glass: Glass cooled gradually during manufacture in an annealing operation to reduce residual stresses and strains that can occur during cooling. Technically, the stress condition of ordinary glass which is glass that can be cut and processed. This is the normal cuttable glass that is generally available.
Annealing: In the manufacturing of float glass and obscure 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.
Annealing Lehr: An on-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 inherent in the flat glass product to allow normal cold end cutting and processing.
Annealing Point: Temperature at which the viscosity of the glass is approximately 1013 Poises. At the annealing point of glass, internal stresses are substantially relieved in a matter of minutes.
Anti-Bandit Glazing: A type of security glazing, typically laminated glass, designed to resist manual attack and to delay access to the protected space for a short period of time.
Antique Glass: Glass with an uneven surface texture and bubbles inside, produced by using antique methods in order to obtain the appearance of glass made before the development of industrial processes.
Application Life: Period of time during which a sealant can be effectively applied to a joint. The timing is from completion of mixing and could be affected by temperature, humidity or a combination of both. Also known as Working life.
Argon: An inert, non-toxic gas placed between glass panes in an insulated glass unit in order to improve the insulating properties of the unit.
Arris: A small bevel at an angle of approximately 45 degrees to the edge points of the glass, applied usually with a wet or dry belt, stone or machine.
Arrised Edge: The result of removing sharp edges.
Aspect Ratio: The ratio of the longer side of a panel to its shorter side.
Asymmetrical Material: Material is asymmetric when it is composite and some of the components are of different thicknesses.
Attenuation: The reduction of sound intensity (or signal strength) with distance. Attenuation is the opposite of amplification, and is measured in decibels.
Austint: A now superseded trade name for the Viridian range of tinted float glass. Now known as VFloat.
Autoclave: A pressure tank vessel that employs high pressure and heat to produce bonding between glass and PVB or urethane sheet, creating a PVB laminated glass product.
AWA: - Australian Window Association - has been formed to bring together for the benefit of window manufacturers. Website:: www.awa.org.au

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B

Backing 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 hourglass contour of the finished sealant bead.
Back: Clearance Space between the surface of the glass and the back of the rebate.
Back Putty: That portion of the compound remaining between the back of the rebate and glass after the glass has been pressed into position in the bedding putty.
baluster: A vertical member supporting a handrail and forming part of a balustrade.
Balustrade: A framed or unframed barrier between handrail and floor level (see also handrail).
batter: A surface defect that looks like hammered metal. Unless very heavy, it usually cannot be seen by the naked eye, although it can be clearly seen on the shadowgraph.
Bead: A strip of timber, aluminium or other suitable material secured to the rebate to retain the glass in place (sometimes referred to as a glazing bead).
Bed or Bedding: The glazing material used to seal between the glass and frame/bead.
Bedding or Stop: In glazing, the application of compound 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.
Bending: The process of manufacturing bent glass.
Bent Glass: Glass produced by heating annealed glass to the point where it softens and which then can be pressed or sag-bent over formers. Bends can be created in one or two planes. Bending can be incorporated in the toughening process. Bent glass can also be laminated.
Bevel: A sloping edge on a glass sheet commonly used on mirror glass.
Bevelling: The process of grinding and polishing a sloped angle on the face of the edge of flat glass which results in a decorative edge appearance to the glass.
Bevel Both Sides: The edges to both surface sides of the glass are bevelled to the usual standard bevel.
Bevel To Butt: The process of producing a small mitre bevel to butt edges typically on mirrors.
Bite: Also referred to as structural bite, is the width of silicone sealant that is applied to the panel of glass to adhere it to the frame.
Bleeding: Migration of colour from the coating film onto or into a surface with which it comes in contact.
Blibe: An elongated bubble larger than seed.
Blemish: A noticeable imperfection in or on the surface of the glass.
Blisters: A profusion of bubbles or gaseous inclusions in glass. Small bubbles less than 2mm diameter are referred to as seeds.
Block: A small piece of lead, wood, santoprene or rubber or other suitable material used to position glass in a frame. Refer setting blocks.
Bloom: A surface film on glass resulting from atmospheric attack or deposition by smoke or other vapours.
Blow-in: A separation of glass and interlayer at or close to the edge of laminated glass caused by penetration of the autoclaving medium into the edge during laminating.
Body Tinted Glass: Glass produced by the addition of metal oxides to the molten glass which do not materially affect the basic properties except for the colour and solar energy transmission.
Bow: A curve, bend or other deviation from flatness in glass.
Break Pattern: The resultant pattern formed by the cracks within an individual pane of glass when broken.
Breather Tube Units: An insulating glass unit with a tube factory-placed into the unit's spacer to accommodate pressure differences for units being installed at high altitudes. These tubes must be sealed on the job site prior to unit installation.
Brewster's Fringes: A rainbow effect sometimes seen in double glazing caused by the light refraction from identical thicknesses of glass.
Brilliant Cut: Decorative process in which designs are cut into glass with abrasive and polishing wheels.
British Thermal Units (BTUs): The amount of energy (in imperial units) needed to raise one pound of water from 63°F to 64°F.
Bronze Glass: See tinted glass.
Bubbles: In float glass and obscure glass, a gaseous inclusion. In laminated glass, a gas pocket in the interlayer material or between the glass and the interlayer. Also called a blister or seed.
Bulb Edge: In float glass manufacture, the extreme lateral edge of the ribbon as floated down the line.
Bullet Resistant Glass: A multiple lamination of glass and plastic that is designed to resist penetration from medium-to-super-power small arms and high-power rifles.
Bullion: A glass panel having a formed antique style circle in its centre for decorative effect. Originally the cut-out bottom of a mouth blown glass cylinder.
Bull Nose: The rounding, in the form of a quarter circle, of half of the cut edge of the glass. The remaining surface edge is slightly rounded. Also known as half round.
Butt Glazing: The installation of glass products where the vertical glass edges are glazed with silicone and without structural supporting mullions.
Buttering: Application of sealant or compound to the flat surface of some member before placing the member in position; for example, the buttering of a removable stop before fastening the stop in place.

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C

CAD: Processing Computer Aided Design, the use of a computer to produce graphics.
Calories: The amount of energy needed to raise one gram of water from 14.5°C to 15.5°C.
Cantilevered Balustrade: The use of glass in a balustrade where it forms a structural enclosure or barrier. The glass is installed or cement fixed directly into channels or with fixings and the glass takes all loads directly back to its fixing point.
Capillary Tube Units: An insulating glass unit with a very small metal tube of specific length and inside diameter, factory-placed into the unit's spacer to accommodate pressure differences encountered in shipping to high altitudes. (See also Breather Tubes).
Casement Window: A window, pivoted or opening on side hinges.
Cast-In-Place Lamination (CIP): Lamination process where the interlayer is obtained by pouring a liquid between plies of glass or plastics glazing sheet material, which is then cured to produce the final product.
Cast Glass: Glass produced by 'casting', in other words by pouring molten glass into a mould or by heating glass in a tank and extruding it through patterned rollers.
Central Area of Sheet: The area that forms an oval or circle centred on the sheet, whose axis or diameter does not exceed 80% of the overall dimension. This allows a fairly large area at the corners, which may have imperfections that are not allowed in the central area.
Centre Tension: Residual tension stresses within the centre (core or zone) between the surface compression layers of thermally toughened and heat-strengthened glass.
Ceramic Enamel: A combination of crushed glass, metal oxide colourants and flux mixed in an oil or water medium and fused onto glass. Also known as ceramic ink.
Cerium Oxide: The oxide of the rare earth group, used alone or together with other substances as a polishing agent for glass.
Chair Rail: A fixed glazing bar or rigid push bar that provides protection from human impact. Also known as a crash rail.
Channel Depth: The measurement from the sight line of the frame to the bottom of the channel.
Channel Glazing: A three-sided, U-shaped opening in sash or frame to receive light or panel. Also known as perimeter channel.
Channel Width: The distance between the fixed and removable beads at the widest point.
Checks: Very small cracks in flat glass, usually at the edge. Though small, these are cause for concern since they can be intensified under strain (See Edge Vents).
Chemical Durability: The lasting quality, both physical and chemical, of a glass surface. It is frequency evaluated after prolonged weathering or storage, in terms of physical and chemical changes in the glass surface (see Weathering).
Chemically Toughened Glass: Chemical strengthening of glass is brought about through a process known as ion-exchange. Glass is submersed in a molten salt bath at temperatures below the annealing range of the glass. In the case of soda lime silica glass, the salt bath consists of potassium-nitrate. During the submersion cycle, the larger alkali potassium icons exchange places with the smaller alkali sodium ions in the surface of the glass. The larger alkali potassium ions 'wedge' their way into the voids in the surface created by the vacating smaller alkali sodium ions. This 'strengthened' surface may penetrate to a depth of only a few microns. It is not a recognised safety glass.
Chip: A small shallow piece of glass which has become detached from the original glass edge or face or the void it has left.
Chipped Edge: An imperfection due to the breaking of a small fragment from the cut edge of the glass. Generally this is not serious except in heat absorbing glass.
Chord: A straight line (or measurement), joining ends of an arc.
CIP (Cast In Place): Lamination process where the interlayer is a liquid poured between two plies of glass and then chemically or UV cured to produce the final laminated glass product.
Cladding Glass: Toughened or Heat strengthened glass usually painted or silk-screened using ceramic ink as a colouring agent for use in curtain walls or as a cover to columns and walls. (See also Spandrel).
Clear Glass: Architectural clear glass is almost invariably of the soda-lime-silica type. Composition varies with manufacturer but is generally silica (SiO2) 70% to 74%, lime (CaO) 5% to 12% and soda (Na2O) 12% to 16%, with small amounts of magnesium, aluminium, iron and other elements.
CNC Processing: Computer Numeric Control. This type of machinery enables the processing of sophisticated shapes and hole contours in glass.
Cohesive Failure: Internal splitting of a sealant resulting from over stressing and insufficient elasticity and elongation to absorb the strain.
Coincidence Dip: The frequency at which a glass panel vibrates in unison with the frequency of the incident sound pressure waves thus significantly reducing the sound insulating properties of the glass at that specific frequency.
Colonial Bars: Horizontal or vertical bars that divide a sash frame into smaller panels of glass. Colonial bars are smaller in dimensions and weight than mullions. They are sometimes surface fixed to glass.
Colour co-ordinated: A system that can be used to assign numbers to specify or describe the colour of glass or the colour of coating on glass.
Colour Variation: Noticeable colour differences between glass panels, or within one panel of glass or coated glass.
Compression: Pressure exerted on the glazing compound sealant, tape or gasket by the glazing method.
Condensation: The appearance of moisture (water vapour) on the surface of glass caused by warm moist air coming into contact with the colder surface of the glass.
Conduction: Heat transfer in which there is a direct contact of molecules in a solid body, e.g. the passage of heat along a metal bar of which one end is inserted into a fire.
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, and the like.
Convection: Heat transfer in which actual movement of the medium, gas or liquid occurs e.g. heated air from a convection heater.
Coolness Factor: (See Luminous Efficacy).
Cords: Attenuated glassy inclusions that possess optical and other properties differing from those of the surrounding glass. Cords are the result of non-homogeneity. Low intensity cords are called strings, wire lines or ream.
Corners On/Off: Section of glass remaining on or removed from the corner of a sheet, caused by the score mark not continuing right through to the traverse mark.
Covered Edge: The perimetric area of the glass covered by the channel or sash when installed. Also known as edge cover.
Countersunk Hole: A hole which has been ground out at the surface to receive a mechanical fixing, allowing the bolting or fixing of the glass panel.
Crash Rail: A rail, together with its fixings, capable of withstanding a load of 750N per metre length, acting in any direction without contact with the glazing material.
C.T.S: Abbreviation for cut-to-size glass.
Cullet: Broken glass , the excess glass from previous glass manufacture or edge trims off the cutting of glass to size. Cullet is an essential ingredient in the pre-melt raw glass mix as it facilitates the melting process.
Curing Agent: One part of a two-part sealant, which, when added to the base, will cause the base to change its physical state by chemical reaction between the two parts.
Curtain Wall: A non load-bearing wall of metal sections, glass and infill panels, which is carried directly by the structure of a building. Extensively used in modern high-rise office buildings.
Cutout: The removal of a section of a glass panel.
Cut sizes: Any flat glass cut to specific dimensions. Also known as cut-to-size
Cutter: (a) A person who cuts glass. (b) The tool used in cutting glass.
Cutting: Scoring glass with a diamond, steel or hard alloy wheel and breaking along the score.

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D

Damage Weighted: The measurement of the relative fading reduction over the whole solar spectrum, not just ultra violet. It is weighted to address the fact that fading results from a broad band of solar energy.
Daylight Size: The clear height and width between frame members that admits light.
Decal: A specially prepared paper on which designs have been printed for the purpose of transferring to glass.
Decolourizing: The process of producing a colourless appearance in glass.
Decorated glass: Clear or patterned glass processed by craftsmen for decorative effect. Stained glass, leadlights and sand-blasted, acid-etched, embossed and printed glass fall into this category. Decorative interlayers can also be incorporated in laminated glass.
Decorating: (a) Firing enamels onto glassware. (b) Applying designs to formed glassware by means of etching, sandblasting, cutting, engraving or similar methods.
Deflection (centre of glass): The amount of bending movement of the centre of a glass panel, perpendicular to the plane of the glass surface under load (usually wind load).
Delamination: A condition in which one or more of the glass plies of laminated glass loses the bond with the interlayer. Often it is a minor edge discolouration reaction from sealant.
Desiccant (Silica Gel): Molecular sieve or extremely porous crystalline substance used to absorb moisture inside the air space of insulated glass units.
Design Wind Pressure: The specified pressure a product is designed to withstand.
Devitrification: Crystallization in glass.
Dew Point: The temperature at which condensation of moisture begins when air is cooled.
Dice: The more or less cubicle (cubic?) pattern of fracture of fully tempered glass, the edges of the dice being roughly equal to the thickness of the glass (see break pattern).
Dichroic Coatings: Multi-layered coatings that exhibit different colours by reflection and transmission as a function of viewing angle.
Dielectric Coating: A flexible, electrically insulating coating suitable for application by spraying, dipping and syringe dispensing. NOTE: The range of performance available from the use of metallic coatings is limited because of the thickness of coating that has to be applied. The use of dielectric coatings, which produce interference effects, allows higher light transmission with increased selectivity; the range of colours is also increased.
Dielectric Constant: The ratio of the electric energy of the field set up in a dielectric material to that set up in a vacuum. At a given frequency, it is the ratio of the capacitance of the capacitor with the glass material as the dielectric to the capacitance of the same capacitor with a vacuum as the dielectric.
Diffuse Reflection: Glass used in picture framing to avoid reflections and the glare of lighting.
Diffusing: Scattering, dispersing, as the tendency to eliminate a direct beam of light.
Digs: Deep, short scratches.
Diminishing Stop Bevel: A bevel in which only a portion of the surface edges is bevelled, the bevel running out on a small radius.
Direct Transmittance: That portion of the sun's emitted solar heat energy which is directly transmitted through the glazing.
Distance Piece (Shims): Small blocks of resilient, non-absorbent material (such as extruded rubber) used to prevent the displacement of glazing compound or sealant by external loading. They are positioned opposite each other between the glass and rebate, and glass and bead.
Distortion: Alteration of viewed images caused by variations in glass flatness and is an inherent characteristic of glass that has been heat treated.
Double Bevel: The surface edge of the glass on the face that is bevelled, the bevel consisting of two intersecting planes.
Double Glazing: In general, any use of two panels of glass, separated by an air space, within an opening to improve insulation against heat transfer and/or sound transmittance. 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
Draw Lines: Refers to the direction of flow (or pull) of the glass during production of sheet glass. Float glass has eliminated this issue.
Drop Height: The vertical distance used from the horizontal centre-line of the maximum diameter of the impacting object when it is released, relative to the horizontal centre-line of the impacting object when it is at rest.
Dry Glazing: Also called compression glazing. This term is used to describe the glazing or sealing in of single glass or insulating glass in the supporting framing system without wet sealants using pre-formed and extruded materials such as glazing gaskets and wedges.
Dry Seal: A weather seal between the glass and frame using foam tapes or gasket materials. Note: A dry seal may not be completely watertight.
Dual Seal: Insulating Glass units manufactured with a primary seal and a secondary seal for maximum protection against moisture vapour transmission.
Durometer: An instrument for measuring the relative hardness of materials such as rubber. Also, the term often used (loosely) as a synonym for relative hardness.

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E

Edgebanding: The 'painting' or 'cladding' of the perimeter edge of glass panels prior to toughening which results in a fused colour to the edge for protection of sealants and adhesives against UV degrading.
Edge Blocks: Rubber blocks that prevent glass from moving sideways in the glazing rebate from thermal effects or vibration.
Edge Cover: The distance between the edge of the glass and the edge of the rebate forming the sight opening of the window frame.
Edge Compression: The compression stresses (similar to surface compression) measured at the very edge of a heat-treated light of glass. The values of compressive stresses may vary on each edge of a given light.
Edge Defects: Glass defects that include vents, shells, flakes, chips, wave, shark's teeth, nibs, corners on/off.
Edge Vent: Cracks that run in from the edge of the glass.
Edge Work: Grinding, smoothing, bevelling or polishing the edge of flat or shaped glass.
Elastomeric: Being of an elastic, rubber-like substance, such as natural or synthetic rubber.
Emissivity: The ability of a material to emit radiant energy. Emittance is the ratio of the total radiant energy emitted by a given surface to that emitted by an ideal black body at the same temperature. To emit is to give out, to discharge. In the case of glass, essentially, to re-radiate absorbed energy (heat).
Engraving: Abrading the surface of the glass to achieve decorative designs by means of copper wheels, diamond points, carborundum pencils and other flexible drive tools. The engraving can consist of 'brilliant' cutting of various geometric shapes in the glass surface, which can be further polished.
Environmental Control Glass: A broad name for all types of glass that have a function in controlling noise, heat, glare or radiation (see also Solar Control).
Etch: To alter the surface of glass with hydrofluoric acid or other caustic agents.
Exposed Edge: A glass edge that is not covered. NOTE: Glass with exposed edges has no protection from damage, and may cause injury to those who come in contact with it.
Exterior Glazed: Glass inserted from the exterior of the building.
Exterior Stop: The removable moulding or bead that holds the glass in place when it is on the exterior side of the glass, as contrasted to an interior stop located on the interior side of the glass.
External glazing: Glazing, either side of, which is exposed outside the building.

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F

Façade: The whole exterior of the side of a building that can be seen in one view - generally the front.
Face Mitre: The application of a machined mitred edge to the front surface of a pane of glass, which will result in the butting pane aligning to the face of the glazing.
Faceted Glazing: Glazing with vertical strips of glass (facets) joined at the vertical edges with silicone joints to typically form a radius window
Faults: Faults and imperfections, which include the following: (a) Bubble (b) Blemish (c) Bloom (d) Seed (e) Chip (f) Feather
Feather Edge: Any bevelled edge where the bevel is brought as close as practicable to the back edge of the glass.
Fenestration: Any glass panel, window, door, curtain wall or skylight unit on the exterior walls providing joinery to the building.
Fiery: Poorly annealed glass that results in poor cutting from residual tension or bowing.
Figured Glass: Glass that is generally produced by the rolled process (see 'rolled glass'). The surface of the rollers used carry the pattern or design to be 'imprinted' in the glass as it passes between them. The process gives the glass a textured surface on one or both sides. The surface finish may be both decorative and functional. Apart from the huge variety of patterns possible, figured glass can also offer light dispersion and glare reduction characteristics. Also known as 'patterned' or 'obscure glass'.
Finger Slots: The slot produced by processing the surface of the glass by grinding in a slot for use as a finger grip in sliding the glass panels.
Finished Size: The finished size of the glass after cutting and processing is complete.
Fins: Supporting glass panels, usually vertical, located at a 90° to the glazed surface, usually behind a butt joint.
Fire Cracks: Small cracks penetrating the surface of the glass usually in the shape of short hooked crescents.
Fire-Rated Glass: Glass that resists the penetration of flames and/or smoke for a period of time, in accordance with appropriate Standards.
Fire-Resistant: Laminated Glass Laminated glass containing an interlayer that reacts to high temperature to give the product its fire resistance. This product may also contain glass components that are themselves fire resistant.
Firing: A process to produce permanent colours on glass by firing ceramic colour onto the glass surface at high temperature (600°C).
Fisheye: Defect in coating film, generally a circular depression, usually resulting from contamination of the substrate surface; the coating flows away from the contaminant.
Fixing: Any item that is used to secure - (a) members of a window assembly to each other; (b) an item of hardware to a window member; (c) a completed window assembly into the building structure.
Fixing Compound: A material used in fixing glass, applied by hand, knife or trowel, or as a pre-formed strip, and capable of adhering to a wide variety of surfaces.
Flange: Bevel-like protrusion above the cut edge, but different from a corner-on in that it often has a razor sharp edge.
Flare: A protrusion on the edge of a panel of a glass.
Flashing: An impervious membrane or material which must be compatible with the framing materials and fitted in such a manner as to waterproof (the installation in-delete?) the building.
Flat Glass: A general term that describes construction float glass, sheet glass, plate glass and rolled glass.
Flat Ground Edge: Glass, the cut edges of which are machine ground flat and the surface edges are slightly arrised without a final polish.
Float Glass: A transparent glass, the two surfaces of which are flat, parallel and fire polished so that they give a clear undistorted vision and reflection. Float glass is manufactured by floating a ribbon of molten glass over a bath of liquid tin which has a greater density than that of glass.
Flush Glazing: Glass glazed to an aluminium frame without any external mullion or transom projections.
Foot-lamberts: A unit of brightness equalling one lumen (the basic unit of light) per one square foot of a perfectly white, completely reflectant surface. Brightness in foot-lamberts = Illumination in lumens ´ (P? p?)ercentage of reflectance
Formed Glass: Glass that has been heat-treated to mould patterns or designs into the surface of glass. Also known as slump glass.
Frame: A structure manufactured from timber, metal, glass, or other durable material or combinations of materials, such as glass fins and structural sealant supporting the full length of all the edges of the glazed panel.
Fracture Pattern: The resultant pattern formed by the cracks within an individual light of glass when broken.
Frit: Raw materials mixed together and melted to form glass.
Front Clearance: The space between the face of the glass and the bead.
Front Putty: A triangular fillet of putty formed between the surface of the glass and the rebate platform, or that portion of compound remaining between the bead and the glass, on completion of glazing.
Frosted Finish: A surface treatment for glass, consisting of acid etching or sandblasting of one or both surfaces to diffuse transmitted light.
FRR: Fire Resistant Rating. The classification given to a glass type or glazing system to resist fire, relative to certain measurements.
Fuse: A glass particle or crystalline material that is permanently bonded to a surface of a light or pane of glass.

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G

Gas-filled: The filling of the cavity of a sealed, insulating glass unit with a special gas to enhance the thermal insulation and/or acoustic properties.
Gaseous Inclusions: Round or elongated bubbles in the glass.
Gaskets: A pre-formed resilient rubber-like compound providing a continuous surround for glass and a weather tight seal when compressed.
Georgian Wired: Glass Incorporating wire mesh square pattern. The glass may be cast or clear polished.
Gilding: A process employed largely for lettering and decorative work, whereby leaf metal such as gold leaf is applied to the glass surface and coated with a protective medium.
Girth: The measurement around the perimeter of a curve or bend.
Glare: The discomfort or impairment of vision, or both, caused by extreme contrasts in the field of vision, where parts such as lamps, the sky, the sun or reflecting surfaces are excessively bright in relation to the general brightness of surroundings.
Glass Block: A rectangular or square hollow block made of cast glass, and produced in a range of shapes for use in non-load-bearing partitions. Glass blocks are usually translucent, produce an even distribution of light, and are patterned on the interior or exterior face(s) to obscure through-vision.
Glass Brick: See Glass Block
Glass Clad Polycarbonate: Two or more panels of flat glass bonded with a urethane interlayer to one or more sheets of extruded polycarbonate in a pressure/ temperature/vacuum laminating process.
Glass Fin: A piece of glass positioned to provide lateral structural support to a glass wall.
Glass Flooring: Composite of three or more layers of annealed or toughened glass with highly tear resistant interlayers with a non-slip coating fused onto the upper surface.
Glass Stop: A small timber moulding or metal section for holding glass in place, usually rectangular, or with a rounded or bevelled edge (see Glazing Bead).
Glazing Bar: An aluminum extrusion typically used for glazing systems in roofs.
Glazing: 1 The securing of glass in prepared openings in windows, door panels, partitions, and the like. 2 Glass or plastics glazing sheet material for installation into a building.
Glazing Bead: A small timber moulding or metal section for holding glass in place, usually rectangular, or with a rounded or bevelled edge. Also called 'Glass Stop'.
Glazing Quality: In float glass, the standard glass supplied to buildings when quality is not otherwise definitely specified
Glazing Compound: A material used in glazing, applied by hand, gun, knife or trowel, to provide bedding for the glass and a weather-tight joint between the glass and frame.
Glazing Gasket: Plastic or synthetic rubber extrusion used between the glass and the frame or the glass and the bead.
Glazing Groove: A groove made to receive glass.
Glazing Panel Size: The actual size of the pane of glazing material.
Glazing System: Any combination of glass and/or any other material that fills a window opening.
Glazier's Putty: A stiff, dough-like material consisting of chalk whiting and linseed oil with white or other pigment. Used for setting window panes in timber sashes or filling (stopping) imperfections or crevices in other surfaces
Glazing Shoe: A mechanical fixing at the end of a sloped glazing bar to stop the glass panel sliding or protruding past the bar at the gutter or exposed end.
Glue Chip: Decorative glass produced by sticking material onto the glass with a glue. As the glue cures the material is stripped off the glass, the surface of which is plucked. This gives a random pattern.
Greenhouse Effect: The description applied to the phenomenon that keeps the planet warm. The earth's atmosphere transmits short-wave solar energy, but then traps the absorbed solar heat that re-radiates in the form of long-wave infra-red radiation. It is a misconception that greenhouses become warm because of the greenhouse effect. The glass in an ordinary greenhouse acts as a convection trap rather than a radiation trap.

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H

Handrail: A horizontal or sloping rail(ing) at about waist height, which is grasped by the hand for support and which forms a safety rail to guard the side of a stairway, landing, elevated platform, walkway or bridge. Handrails form the top of the balustrade on open sides and are supported on handrail brackets on enclosed (wall) sides.
Hard Coat: Coating applied to glass during its manufacture whereby it is fused to the glass in the form of a pyrolitic coating. It is very durable and can be cut and toughened from stock.
Heat Absorbing Glass: Glass that absorbs amounts of solar energy (e.g. tinted glass).
Heat Gain and Heat Loss: Heat gain occurs in the summer months, when the exterior temperature is above the interior temperature and the heat flows inward. Heat loss occurs in the winter months, when the interior temperature is warmer than the exterior temperature and heat flows outward. Heat gain or heat loss are generally measured by U value.
Heat-Reflecting Glass: Surface-treated glass that reduces solar heat gain through reflection.
Heat-Resisting Glass: Glass with a low coefficient of expansion, which is therefore less liable to thermal shock. Borosilicate is the most common type of heat-resistant glass.
Heat Soaking: Heat soaking is the process whereby toughened glass is reheated for a period of time at high temperatures to induce breakages that may be caused by inclusions or contaminants in the glass.
Heat Strengthened Glass: Flat or bent glass that has been heat treated to a specific surface and/or edge compression range. Heat strengthened glass is approximately twice 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 will not completely fragment as will fully toughened glass
Heat-strengthened Laminated Safety Glass: Laminated safety glass utilizing two or more panels of heat strengthened glass in the make-up.
Heat Transfer: Heat is transferred in the following manner: Conduction - in which there is direct contact of molecules in a solid body, for example; the passage of heat along a metal bar of which one end is inserted in a fire. Convection - in which actual movement of the gas or air occurs; for example, heated air from a convection heater. Radiation - by which heat passes from source to object without heating the space between them; for example, heat from the sun to earth.
Heat Treated: Annealed glass heated to a temperature near its softening point and forced to cool rapidly under carefully controlled conditions. Heat-treated glass may be either heat strengthened or fully toughened (fully tempered).
Heel Bead: Sealant applied at the base of a window channel, after setting the glass panel and before the bead is installed. One of its purposes is to prevent air and water penetration.
Hermetically sealed: Made airtight by fusion or sealing. Insulated Glass Units are hermetically sealed.
High light transmission glass: Transmits a high percentage of visible light. Also known as low iron glass.
Hopper: A sash hinged at the bottom and often fitted with side checks to prevent cross draughts in a room.
Horticultural glass: Used for glass houses and other horticultural applications.
Hydrofluoric acid: A highly corrosive acid that attacks silicates such as glass. Pure Hydrofluoric acid dissolves glass, leaving a brilliant, acid-polished surface.

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I

Inclusion: A crystalline or non-crystalline particle entrapped in glass.
Infra-red: That part of the solar spectrum that is invisible to the human eye (780 to 2500nm).
Insulating Glass Unit (IGU): Two or more panes of glass spaced apart and factory sealed with dry air or special gases in the unit cavity. Often abbreviated to IGU or DGU and referred to as a unit.
Interlayer: Plastic material used between two or more glass panels in the manufacture of laminated safety glass to bond the glass together.
Intumescent Interlayer: A type of interlayer in fire-resistant laminated glass, which becomes opaque when exposed to fire.
Iridescence: A surface rainbow effect similar to an oil-on-water appearance. Normally caused by atmospheric moisture or alkali attack.
Irregular Shape: A shaped piece of glass that is not a straight edged rake and cannot be expressed as a size on paper without a diagram.

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J

Jamb: Vertical frame member at the perimeter of the opening of a window or door.

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K

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Information provided is issued as a guide only, and should not be treated as a substitute for detailed technical advice. CSR Building Products Pty Ltd disclaims any liability for loss or damage suffered from the use of such data. To the best of our knowledge, all information is believed to be correct at the time of publishing.