• Airspace – The space in the cavity between two glass panes in an insulated glass unit
  • 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.
  • 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.
  • Arrissed – A basic form of edgeworking, by removing the sharp edges of cut panes of glass.


  • Balustrade – A barrier or form of guarding, generally waist-height, which protects people from falling where there is a change in floor level, for example stairs and balconies.
  • Bed or Bedding – The glazing material used to seal between the glass and frame/bead.
  • 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.
  • Bevelled – A decorative form of edge working, where the edges of a glass pane are ground and polished smoothly at an angle.
  • 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.
  • Brilliant Cut – Decorative process in which designs are cut into glass with abrasive and polishing wheels.
  • 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.
  • 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.
  • Butt Glazing – The installation of glass products where the vertical glass edges are glazed with silicone and without structural supporting mullions.


  • Cavity – The void/space formed by the spacer bar between the two panes of glass in double-glazed units, and nowadays is generally filled with argon for enhanced thermal insulation.
  • Ceramic Frit – See “Enamelled glass”.
  • Chamfer – A small bevelled edge connecting two surfaces. If the surfaces are at right angles the chamfer will typically be symmetrical at 450, similar in appearance to arrissing.
  • 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.
  • 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.
  • 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.
  • Counter Sunk – A hole drilled through the glass so that when a screw or bolt is inserted the head of the fixing is flush/level with the surface of the pane. The fixing must be isolated from the glass by nylon or soft lining material; there must be no glass-to-metal contact.
  • 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.
  • Curved Glass – Glass, which is curved in form, produced by heating it to its softening point, so that it takes the shape of the mould. Annealed, toughened and laminated glass is available in curved form.
  • Cut Sizes – Any flat glass cut to specific dimensions. Also known as cut-to-size


  • 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.
  • Desiccant – Generally a pure molecular sieve- or silica gel-based product, the desiccant is placed within the cavity spacer bar of double-glazed units in order to dehydrate or to remove any residual moisture in the unit.
  • 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.
  • Dubbed Corner – The removal or blunting of sharp corner edges, often done in conjunction with arrissing, again it might be referred to as a chamfered corner.


  • 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.
  • Edge Work – Grinding, smoothing, bevelling or polishing the edge of flat or shaped glass.
  • Enamelled Glass – One face of the glass is enamelled, by applying a ceramic frit that is then fired into the surface of the glass at high temperature. Depending on the cooling regime employed, this then results in either a heat-strengthened or thermally toughened glass.


  • Fins – Supporting glass panels, usually vertical, located at a 90° to the glazed surface, usually behind a butt joint.
  • Fire – Rated Glass-Glass that resists the penetration of flames and/or smoke for a period of time, in accordance with appropriate Standards.
  • Flat Glass – A general term that describes construction float glass, sheet glass, plate glass and rolled glass.
  • 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.
  • Formed Glass – Glass that has been heat-treated to mould patterns or designs into the surface of glass. Also known as slump glass.
  • Free Standing Barrier – A structural barrier where the glass is fixed to the structure, either adhesively or by clamping, along its bottom edge and has a continuous handrail attached to the top edge. The glass is designed to withstand all the imposed design loads and there are no balusters.
  • 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.
  • Frosted Finish – A surface treatment for glass, consisting of acid etching or sandblasting of one or both surfaces to diffuse transmitted light.


  • 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 Stop – Fitting attached to the lower end of a glazing bar to prevent the infilling (glass) from sliding/slipping.
  • Glazing/Glass Size – The dimensions of the cut glass ready for installation, clearances having been allowed. As a general rule the industry gives width first and height second (w x h).
  • 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’.


  • 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-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-Strengthened Glass – Glass which has been heat-treated in order to increase its mechanical strength and resistance to thermal breakage. It has fracture characteristics similar to that of ordinary annealed glass and is not classed as a safety glass.
  • Heat-strengthened Laminated Safety Glass – Laminated safety glass utilizing two or more panels of heat strengthened glass in the make-up.
  • Heat Soak Test (HST) – This is an additional form of heat-treatment, which is carried out after the thermal toughening process in order to reduce the risk of spontaneous breakage of toughened glass in service due to nickel sulphide inclusions.
  • 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).
  • High Light Transmission Glass – Transmits a high percentage of visible light. Also known as low iron glass.
  • Hydrofluoric Acid – A highly corrosive acid that attacks silicates such as glass. Pure Hydrofluoric acid dissolves glass, leaving a brilliant, acid-polished surface.


  • Inclined Glazing – Glazing that is inclined at an angle between horizontal and 75° from horizontal.
  • Infill Panel – The term applied to the glass panel underneath the handrail in a barrier that provides containment, but no structural support to the main frame of the barrier.
  • 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.
  • Intumescent Interlayer – A type of interlayer in fire-resistant laminated glass, which becomes opaque when exposed to fire.
  • Interlayer – Plastic material used between two or more glass panels in the manufacture of laminated safety glass to bond the glass together.


  • Laminated Glass – A composite material consisting of two or more sheets of glass permanently bonded together by a plastic interlayer material. NOTE: Laminated glass will crack and break under sufficient impact, but the glass will tend to adhere to the plastic interlayer instead of falling apart.
  • Location Blocks – Small blocks of resilient material placed between the edges of the glass and frame to maintain edge clearance and to prevent relative movement between the glass pane and surround. Blocks used on the bottom edge of the glass are known as “setting blocks”.
  • Low Emissivity Glass (Low E) – Commonly known as ‘Low-E’ glass and often used in double and triple glazing units, this window glass has a special thin film of metallic oxide coating that allows the passage of short wave solar energy into a building but prevents long-wave energy produced by heating systems and lighting, from escaping outside. Low-E glass allows light to enter while also providing thermal insulation.
  • Low Iron Glass – Very low in iron content and consequently is extremely white and clear and transmits an exceptionally high percentage of visible light.


  • Manifestation – Making glass visible. The marking of glass so as to minimise the potential for human impact and injury.
  • Mirror Silvering – A chemical process depositing a coating of metal, mostly silver, onto the surface of clear glass. This deposit is usually protected by a layer of copper, which in turn is protected by a paint backing. The silver gives the mirror its reflective properties.
  • Mitre Bevel – The bevelling of the cut edge of the glass to an angle of approximately 45° (unless otherwise specified); the extreme point is slightly arrised. Also known as Mitre.
  • Mullion – A vertical framing section between glass panes.
  • Modesty Panels – A panel of toughened shower screen glass silk-screened with a decorative pattern to give a discreet curtain effect.


  • Nickel Sulphide Inclusion (NiS) – A rare, but naturally occurring impurity present in all glass that can, in certain circumstances, lead to spontaneous breakage of thermally toughened glass in service.
  • Notch – Notches and cut-outs are processes whereby areas of glass are removed from a sheet of glass, such an operation might be used where hinges or handles are required on frameless glass doors (there are limitations that apply and advice should be sought).


  • Obscure Glass – (See Patterned Glass).
  • Off-Line Coatings – Applied to individual panes of glass once the glass has been manufactured, taken off line and cut in preparation for further treatment. NOTES: Off-line coatings sometimes called sputter coatings are a soft coat and require special handling and processing. Toughening must take place before the coating is applied.
  • On-Line Coatings – On-line treatment made while the glass is hot and still in the annealing lehr. They may still be considered as basic products, and the size and tolerance constraints are similar to those for clear float glass. Notes: 1. Surface coatings, either for solar control purposes or for reduced emissivity (a property to improve thermal insulation), are called pyrolitic coatings because they are generally applied to the hot glass during its passage through the annealing lehr. They involve the thermal decomposition of gases, liquids or powders sprayed on to the glass to form a metal oxide layer that fuses to the surface. 2. On-line coatings have advantages of hardness and durability over off-line coatings and are suitable for bending and toughening. They tend to be limited in colour/variety.
  • Opacifier – Applied polyester film or coating to the surface of tinted or reflective glass rendering it opaque. Suitable for use in spandrel and non-vision areas.


  • PVB (Polyvinyl Butyral) – The plastic interlayer incorporated into laminated glass in order to ensure good adhesion and the mechanical and safety breakage characteristics of the glass.
  • Patterned Glass – Having a pattern impressed on one or both sides. Used extensively for diffusing light, privacy, bathrooms and decorative glazing. Sometimes called figured rolled or obscure glass.
  • Polishing – A process whereby the surface or edge of glass is polished with felt and a polishing agent, as in polished edges.
  • Poly Vinyl Butyral (PVB) – Interlayer An extremely tough, resilient plastic film used to bond glass together in the laminating process.
  • Putty – A compound used to glaze and seal glass into joinery.


  • Radius Corner – Either an internal or external rounded cut edge on or within a pane of glass.
  • Reflective Glass – Glass with a reflective coating to reduce heat and light transmission.
  • Reflective Coating/Coated – A metallic coating is applied to one side of the glass in order to significantly increase the amount of reflection by the glass of both the visible and infra-red (light and heat) range of the electromagnetic spectrum.
  • Rollerwave – An optical phenomenon, generally noticed in reflection, caused by contact between glass and rollers in the horizontal toughening process


  • Safety Glass – Glass which either must not break or must break safely. Laminated and toughened safety glass are rated Grade A. Wired glass is rated Grade B.
  • Safety Mirror – Mirror which has a sheet of organic material permanently bonded to one side so that the mirror holds together if broken and meets the test requirements of the relevant code.
  • Sandblasting – A surface treatment for glass obtained by blasting the glass with hard particles to obscure one or both surfaces of the glass. The effect is to increase obscurity and diffusion. but it can make the glass weaker and harder to clean.
  • Screen-printing/Screen-printed – Enamelling the surface of a sheet of glass, either partially or completely, by means of a silk-screen and thermal toughening.
  • Security Glass – Thick laminated or multi-laminated glass designed to withstand various forms of violent attack. (Specialist advice should be obtained to assist in the selection of this product).
  • Setting Blocks – Generally rectangular cured extrusions of santoprene, EPDM, silicone, rubber or other suitable material on which the bottom edges of glass are placed to effectively support the weight of the glass and avoid frame contact.
  • Sheet Glass – A transparent glass manufactured by drawing. Sheet glass has natural fire finished surfaces, but because the two surfaces are never perfectly flat and parallel there is always distortion of vision and reflection.
  • Shopfront – The glazed or partly glazed wall at public access level in non-residential buildings with or without a stall board and /or intended for the display of goods or services.
  • Side Panel – A panel (operable or inoperable) located adjacent to a doorway. It may or may not be in the same plane as the doorway.
  • Silicone Sealant – One part or two part elastromeric adhesive, rubber sealant which cures at room temperature, also referred to as room temperature vulcanising (RTV). Its inorganic composition means silicone sealant is unaffected by UV, ozone and extremes of hot and cold. It will not break down or lose adhesion and for this reason is widely used in most glazing applications.
  • Silica – Silicon dioxide, a mixture that is the main ingredient of glass. The most common form of silica used in glassmaking is sand.
  • Sloped Glazing –  Any installation of glass that is sloped more than 15° from the vertical. Where over populated areas, refer Overhead Glazing.
  • Silvering or Silvered – A process used in the manufacture of mirrors, whereby a silver coating is applied to one surface of the glass.
  • Solar Factor G – The percentage of total solar radiant heat energy transmitted through glazing (the sum of energy transmitted directly and energy absorbed and re-emitted to the interior).
  • Slump Glass – Glass that has been heat treated to mould patterns or designs into the surface of the glass.(See also Formed glass)
  • Soft Coats – Coated glass where metal particles have been deposited on the glass by a chain reaction in a vacuum vessel. This is done off line and is sometimes called sputter coating. The coating is soft and less durable than hard coats.
  • Solar Control Glass – Tinted and/or coated glass that reduces the amount of solar heat gain transmitted through it.
  • Spacer Bar – Generally an aluminium bar along all edges of a double-glazed unit, filled with desiccant, which separates the two panes of glass and creates a cavity.
  • Spandrel or Spandrel Panel – Glass cladding panels used in non-vision areas of a facade, commonly in curtain walling. They generally comprise an enamelled or opacified glass to conceal building structure elements such as the edge of floor slabs.
  • Stained Glass – Refers to the craft of lead-lighting – glass which is coloured by fusing pigments to the surface, or windows made up of pieces of stained glass in lead canes.
  • Structural Glazing – Glass acting as a structural support to other parts of the building structure, for example glass fins. It can also refer to glass that is fixed by means of bolted connectors where the glass is not acting as a structural element.
  • Stress Pattern – A specific geometric pattern of iridescence or darkish shadows that may appear under certain lighting conditions, particularly in the presence of polarised light (also called quench pattern). The phenomenon is caused by the localised stresses imparted by the rapid air cooling of the toughening operation. Stress pattern is characteristic of all heat treated glass.


  • Tempered Glass – (See Toughened glass).
  • Template – A pattern used as a guide to produce the desired definition of the overall size and shape of a piece of glass.
  • Tinted Glass – Glass with colourants added to the basic glass batch that give the glass colour, as well as light and heat reducing capabilities. The colour extends throughout the thickness of the glass. Typical tints include bronze, grey, dark grey, aquamarine, green, deep green and blue.
  • Tinted Interlayer – A coloured pvb interlayer between two or more panes of glass.
  • Toughened Glass – Flat or curved glass that has been heat-treated to induce a high surface and /or edge compression. Fully toughened glass, if broken will fracture into many small pieces (dice) which are more or less cubical. Fully toughened glass is approximately 4 to 5 times stronger than annealed glass of the same thickness when exposed to uniform static pressure loads. It is sometimes called ‘Tempered glass’.
  • Toughened Laminated Safety Glass – Laminated safety glass utilising two panels of toughened safety glass in the make-up.
  • Toughened Safety Glass – Glass converted to a safety glass by subjection to a process of pre-stressing so that, if fractured, the entire piece disintegrates into small, relatively harmless particles.
  • Translucent Glass – Glass that transmits light with varying degrees of diffusion so that vision is not clear.


  • Vacuum Coated – The process in which, by passing an electric current through an ionised gas and thus bombarding the surface of a metal cathode with ions, atoms of the desired metal are vapourised and then deposited in a thin film on the surface of glass. Also known as soft coats and sputter coated glass.
  • Vertical Glazing – Glazing which is either true vertical, or within 15° either side of true vertical.


  • Wired Glass – Having a layer of meshed or stranded wire embedded near to the centre of thickness of the panel. This glass is available as polished glass (one or both surfaces polished to make it clear) and patterned glass.