Glossary

Glass industry terms and acronyms explained

All/A/B/C/D/E/F/G/H/I/L/M/N/O/P/R/S/T/U/

The process of scraping, rubbing or wearing away by friction.

The Australian Glass and Window Association is the peak industry body for the Australian glass and fenestration industry who endorse compliant, sustainable and fit-for-purpose products. Using an AGWA member when purchasing window, door and glazing products significantly reduces the risk of purchasing an incorrect product. AGWA business is conducted with honesty and integrity, upholding the right to a fair return for goods and services supplied.

The cavity or space between two glass panes in an insulated glass unit (IGU).

Annealing is the process of controlled cooling to prevent residual stresses in float or obscure glass. Re-annealing is the process of removing stresses in glass. Here the glass is re-heated to a suitable temperature followed by controlled cooling.

Argon is a non-toxic, inert gas placed between glass panes in an insulated glass unit (IGU) to improve insulating properties.

An arris is a small edge bevel applied by a machine to remove the sharp edges from a piece of cut glass.

A framed or unframed barrier, fixed between a handrail and the floor.

A strip of timber, aluminium or material fixed to a rebate to retain glass in place. This is sometimes referred to as a glazing bead.

A sloping edge on a glass sheet often used on mirror glass.

The process of grinding and polishing a slope to the face of the edge, of flat glass resulting in a decorative edge.

An imperfection in or on a glass surface.

An elongated bubble in a piece of glass, larger than seed. Small bubbles less than 2mm diameter are referred to as seeds.

Bubbles or gaseous inclusions in a glass sheet. Small bubbles less than 2mm diameter are referred to as seeds.

A curve, bend or deviation from flatness in a piece of glass.

A type of tinted glass.

In float and obscure glass bubbles are a gaseous inclusion within the glass sheet. In laminated glass, bubbles refer to a gas pocket in the interlayer or between the glass and the interlayer. A bubble can also be referred to as a blister or seed.

CAD refers to computer aided design, or the use of computers to draw technical designs and outlines.

A window that pivots or opens on side hinges.

A small shallow piece of glass that has detached from a piece of glass, or the marking it has left in the remaining glass.

Clear glass is approximately composed of:

  • Silica (SiO2) 70% to 74%
  • Lime (CaO) 5% to 12%
  • Soda (Na2O) 12% to 16%, and
  • small amounts of magnesium, aluminium, iron and other elements.

CNC is an acronym meaning Computer Numeric Control. CNC machines can cut and process complex shapes and holes in glass.

Colour variation refers to colour differences between varying glass panels, or within one panel of glass.

Condensation is moisture that gathers on the surface of glass when warm moist air comes into contact with a cold glass surface.

A circular, bevelled hole, ground out of a glass panel to allow fixing, or bolting of the glass.

CTS is an acronym meaning Cut To Size.

The piece removed, or the space left when removing a piece of glass from a glass panel.

Cutting refers to scoring glass with a diamond, steel or hard alloy wheel and separating the glass along the scored line or shape.

The process of producing a colourless appearance in glass.

That portion of the sun’s solar heat energy which is directly transmitted through glass.

An edge bevel style where the bevel consists of two intersecting planes.

A Double Glazed Unit or DGU refers to two or more panes of glass, factory spaced apart, and factory sealed with dry air or special gases in the unit cavity between the panes of glass. DGU and IGU (Insulated Glass Unit) are often used interchangeably, and are often referred to as a unit.

Double glazing refers to two glass panels separated by an air space. Double glazing provides improved insulation against heat and/or sound transfer compared to single glazing.

Edge work refers to grinding, smoothing, bevelling and/or polishing the edge of a cut glass panel.

A bevelled edge where the front bevel is as close as is practical to the back edge of the glass.

The arrangement and joining of glass windows, doors, walls, skylights or panels in a building.

The finished size of a glass panel, after cutting and all processing is complete.

A term that describes float glass, sheet glass, plate glass and rolled glass.

Transparent glass where the two surfaces are flat, parallel and fire polished so that they provide clear, undistorted views and reflections.

Frosted glass is made by the sandblasting or acid etching a clear sheet of glass. This creates a pitted surface on one side of the glass, and light that passes through scatters, creating the translucent effect. Frosted glass blurs images while still transmitting light and is often used to provide privacy.

Glazing refers to either the securing of glass panels in openings such as windows, doors, partitions etc, or glazing materials associated with a building or project.

Heat absorbing glass can absorb some solar energy, e.g., tinted glass.

Heat gain occurs when exterior temperatures are higher than interior temperatures, and heat flows inward. Heat loss occurs when interior temperatures are higher than exterior temperatures, and heat flows outward. Heat gain or heat loss is measured by U value.

Heat strengthened glass refers to flat 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 when the same thicknesses are compared. Heat strengthened glass is not a safety glass.

Heat treated refers to heating annealed glass to a temperature near its softening point and then force cooling it rapidly under carefully controlled conditions. The process of heat-treating glass can produce either heat strengthened glass, or fully toughened (fully tempered) glass. Toughened glass is a Grade A safety glass in  line with AS/NZS 2208 Australian standards.

Insulating Glass Unit or IGU refers to two or more panes of glass, factory spaced apart, and factory sealed with dry air or special gases in the unit cavity between the panes of glass. IGU and DGU (Double Glazed Unit) are often used interchangeably, and are often referred to as a unit.

Interlayer refers to the plastic material used between glass panels when manufacturing laminated glass. The interlayer bonds the glass together and provides improved thermal and/or acoustic performance.

Laminated glass is a composite material consisting of two or more sheets of glass permanently bonded together by a plastic interlayer material.

Laminated safety glass is laminated glass that satisfies all relevant test requirements for safety glazing material standards.

Light transmission refers to the amount of visible light transmitted through a type of glass, expressed as a percentage.

Low Emissivity Glass or Low E glass, is glass coated with a thin film of metallic oxide that allows light into a building while also preventing heating system and lighting energy from escaping outside. Low E glass is often used in double glazed units (DGUs).

Luminous efficacy refers to the ratio of visible light transmitted by a glazing system relative to its shading coefficient. This ratio assists to identify glasses that transmit more heat than light, or those that transmit more light than heat.

Max height is the maximum manufacturing or processing height for a glass sheet.

Min height is the minimum manufacturing or processing height for a glass sheet.

The standard specifying environmental conditions (i.e. internal and external temperatures) and procedures that are used to determine u-values and performance by glass type.

The relative ability of a coating or material to block the transmission of light.

Solid cover with little if any light transmission.

One of the glass sheets or panels in a laminate.

Polishing refers to the surface or edge of glass being buffed or cleaned with a soft absorbant material and a polishing agent.

Poly Vinyl Butyral or PVB is a tough, resilient plastic film used to bond laminated glass together.

Reglazing refers to repairing or replacing existing glazing, e.g., due to breakage or renovation.

R-Value is the thermal resistance of a glazing system. For higher R-value, less heat is transmitted through the glass or glazing system.

Safety glass has been manufactured and processed to form glass that reduces the likelihood cutting and piercing if the glass breaks on human contact. Safety glass satisfies the requirements of AS/NZS 2208 for safety glazing.

Gaseous bubbles within glass, up to 2 mm in size.

Shading coefficient is the ratio of solar heat gain through glass relative to the solar heat gain through 3mm of clear glass under the same set of conditions..

Solar direct transmittance is the amount of solar energy transmitted through a glass panel.

Solar energy transmittance is the percentage of ultra-violet, visible and infra-red energy, within the solar spectrum, that is transmitted through a glass panel.

Solar heat transmission is the amount of solar energy transmitted through glass relative to the total solar energy on the exterior glass surface.

Solar heat gain coefficient, or SHGC is the ratio of directly transmitted and absorbed solar energy that enters a building’s interior relative to an open space.

Solar reflectance is the percentage of solar energy reflected from a glass surface.

Tempering or toughening  glass refers to the processing of glass with controlled heating and cooling, or chemical treatments, to increase glass strength when compared to normal glass. Tempering also places the outer glass surfaces into compression and the interior into tension. These inherent stresses in tempered glass cause the glass, when broken, to shatter into small granular chunks, instead of splintering into sharp shards as ordinary glass does.

Tinted glass is glass with colourants added to produce colour, and light and heat reducing properties. Bronze and grey glasses are examples of tinted glass.

Total solar energy reflected refers to the ratio of solar energy deflected by a glass panel compared to the solar energy absorbed by a glass panel, expressed as a percentage.

Toughened glass has been heat-treated to induce a high surface compression. When broken, toughened glass fractures into small cube-like pieces. Toughened glass is approximately 4 to 5 times stronger than ordinary glass of the same thickness.

Toughened laminated safety glass is made with two panels of toughened safety glass separated by an interlayer.

Toughened safety glass is glass that has been converted to a safety glass by the toughening process. By subjecting glass to controlled heating and cooling, the glass becomes stronger but is also pre-stressed. When broken or  fractured, safety glass disintegrates into small, harmless pieces.

Translucent glass refers to glass that allows light through but objects on the other side are not seen clearly. Frosted glass is an example of a translucent glass.

Thermal transmittance, or U-value, is the rate of transfer of heat through a glass panel or glass system, divided by the difference in temperature across the panel or system. Lower U-values indicate higher insulation, and high U-values indicate low insulation.

Ultra-Violet (UV) refers to the invisible part of the light spectrum with wave lengths shorter than 380 nanometres. UV is the major factor behind the fading of materials.