A-Z Glass Glossary

A-Z Glass Glossary


In This Guide, We'll Take You Through Some of Those Confusing yet Important Glass Terms and Vocabulary. After This, You'll be up-to-date with The Latest Glazing Terminology and be Confident in Understanding Complex Terms.

A-Z Glass Glossary
In This Guide, We'll Take You Through Some of Those Confusing yet Important Glass Terms and Vocabulary. After This, You'll be up-to-date with The Latest Glazing Terminology and be Confident in Understanding Complex Terms.


Sound and its control - Rw used as the common indicator of how much decibels (dB) is blocked by the glass

Air gap

The trapped and protected air gap in an IGU - commonly filled with Argon gas for further Insulation performance

Annealed Glass

Standard glass before any further heat treating (toughening or heat strengthening)

Argon Gas
An inert gas used commonly in the air gaps of IGU units to add further Insulation properties (lower U-Value)
Like sanding the edges of glass so it is safe to handle with no sharp points


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


A small piece of lead, wood, santoprene or rubber or other suitable material used to position glass in a frame. Refer setting blocks

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
Butt Joint
Where glass on glass is glazed together without a frame, using a silicon sealant

Coated Glass

A coating applied to one of the glass surfaces - commonly Low E coating (Hardcoat or Softcoat)


Glass colour. Standard common float glass is labelled as 'Clear'

Corner joint

Where glass on glass is glazed together at a corner without a frame, using a silicon sealant. Here stepped units can be used

Curtain Wall

Non-load bearing glazing seen in Commercial buildings.


Bending that can occur in glass under pressure eg wind load and altitude changes


Small beads used in some spacer bars of an IGU to help absorb moisture

Design Wind Pressure

The specified pressure a product is designed to withstand


Double Glazed Unit (2x pieces of glass and 1x air gap)
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
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
Dual Seal
Insulating Glass units manufactured with a primary seal and a secondary seal for maximum protection against moisture vapour transmission

Edge Blocks

Rubber blocks that prevent glass from moving sideways in the glazing rebate from thermal effects or vibration


To alter the surface of glass with hydrofluoric acid or other caustic agents



The whole exterior of the side of a building that can be seen in one view - generally the front

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'


A process to produce permanent colours on glass by firing ceramic colour onto the glass surface at high temperature (600°C)

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
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


The filling of the cavity of a sealed, insulating glass unit with a special gas to enhance the thermal insulation and/or acoustic properties


A pre-formed resilient rubber-like compound providing a continuous surround for glass and a weather tight seal when compressed


Float Glass aka Float, Clear, Clear Glass, Annealed, Annealed Glass. Can be clear, tinted, patterned, acid etched, coated, laminated

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 Surface
The sides of a piece of glass. Single glazed glass as 2x surfaces: surface #1 is always outside exposed to the elements while surface #2 will be inside the building and you can touch that surface from inside
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 Bar
An aluminum extrusion typically used for glazing systems in roofs
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 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 System
Any combination of glass and/or any other material that fills a window opening
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

Hard coat

Pyrolytic Coated LowE - uses Indium Tin Oxide as the primary metal and comes with risk of haze appearance

Heat Soak

A process conducted on Toughened glass in a Heat Soak chamber to test for inclusions like Nickel Sulphide. Passing this test offers piece of mind of a very low risk of Spontaneous Combustion

Heat Strengthening

Heated and Cooled in a furnace to be up to 2x stronger than standard annealed glass but not Grade A Safety glass like Toughened glass is

Heat Treating

Further processes to glass - Heat Strengthening, Toughening and Heat Soaking
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 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)
Heat-Reflecting Glass
Surface-treated glass that reduces solar heat gain through reflection
Heat-strengthened Laminated Safety Glass
Laminated safety glass utilizing two or more panels of heat strengthened glass in the make-up
High light transmission glas
Transmits a high percentage of visible light. Also known as low iron glass


Insulated Glass Unit (most commonly a Double Glazed Unit or Triple Glazed Unit)


How well the glazing retains heat inside - measured by the U-Value


Plastic material used between two or more glass panels in the manufacture of laminated safety glass to bond the glass together


Keeps the heat in

Keeping you warmer in winter,controlling the flow of heat to reduce artifical heating

Keeps the heat out

Keeping you cooler in summer, it's the capacity of the glass to direct heat back towards it's source and away from the interiors of your home



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

Laminated safety glass

Laminated glass that satisfies the test requirements of the relevant safety glazing material Standards


A pane or sheet of glass

Light Transmission

A term sometimes used to refer to the amount of visible light transmittance through a type of glass, usually expressed as a percentage
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

Obscure Glass

Patterned Glass


Denoting a solid colour with little if any light transmission



A process whereby glass is first coated with ceramic enamel, and subsequently fired so that the colour becomes permanent

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

Poly Vinyl Butyral (PVB)
Interlayer An extremely tough, resilient plastic film used to bond glass together in the laminating process

Reflective Glass

Glass with a reflective coating to reduce heat and light transmission


An average Weighted Sound Reduction Index of decibels (dB) across a full range of Hertz frequencies - how much dB is blocked from common noise offenders, the higher the value the more noise is blocked


Safety Glass

Glass which is treated or manufactured into a form that reduces the likelihood of a cutting and piercing injury to persons by the glass should it be broken by human contact. These are the manufactured glass types which satisfy the requirements of AS/NZS 2208 for safety glazing. Laminated and toughened safety glass are rated Grade A. Wired glass

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

Soft coat

Sputter Coated LowE - uses Silver (Ag) as the primary metal
Solar Control Glass
Tinted and / or coated glass that reduces the amount of solar heat gain transmitted through it
Solar Energy Transmittance
The percentage of ultra-violet, visible and infra-red energy within the solar spectrum that is transmitted through the glass
Solar Heat Gain Coefficient (SHGC)
The ratio of directly transmitted and absorbed solar energy that enters into the building's interior (when compared to an open space). Solar heat gain includes directly transmitted solar heat and absorbed solar radiation which is then re-radiated conducted or convected
Solar Heat Transmission
The amount of solar energy transmitted directly through glass, compared with the total solar energy impinging on the exterior glass surface. It is typically expressed as a percentage
The component of an insulating glass unit which separates the glass and includes a desiccant, with additional sealant material to prevent air and water penetration
STC (Sound Transmission Class)
A single number rating derived from individual transmittance losses at specified test frequencies. 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




Triple Glazed Unit (3x pieces of glass and 2x air gaps)


Tinted float glass - aka body tinted. Common colours are Grey and Green. Also available as Bronze, Blue, Dark Grey
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
A horizontal intermediate framing member


Frame-Only U-Value


Glass-Only U-Value


Ultraviolet light, not be get confused with U-Value (UV = harmful fading factors that can pass through glass and fade carpets, timber floors, furniture and artwork)


Thermodynamic symbol for heat transfer - Insulation - how much non-solar heat passes through the glass by Watts per m2. The lower the number the less heat loss / the better the Insulation
U-Value w
Total System U-Value (glass + frame + sealants)

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

Visible Light Reflectance

The percentage of visible light (380 to 780 nanometres) within the solar spectrum that is reflected from the glass surface

Visible Light (Solar Energy)

The portion of the solar spectrum that is visible to the human eye (380-780 nm)

Visible Light Transmittance

The percentage of visible light (380 to 780 nanometres) within the solar spectrum that is transmitted through glass


Refers to the type of spacer material used to separate the panes of glass (or glazing) in an insulated window unit. If the material conducts less heat or cold than a conventional aluminium spacer at the edge of the glass, it is said to be 'warm-edge'