Glossary

Absorption
The portion of total incident radiation that is absorbed by the glass and subsequently re-radiated either outside or inside.

Acid Etched Glass
Satin like finish, a translucent glass manufactured by acid-etching one surface of the glass. Products include DécorSatin and Matelux.

Airspace
The space in the cavity between two panes of glass in an insulated glass unit.

Annealing
It is the processed controlled cooling done in a lehr, during the manufacturing of float glass. It prevents residual stress in the glass.

Argon Gas
Argon gas was extensively used in electric lamps, fluorescent tubes, and radio vacuum tubes. In recent times argon gas has been used as a low cost way to decrease heat transfer in insulated glass units. It is a colourless, odourless, inert element.

Aris
Removing the sharp edges of cut panels of glass. This is the minimum edgework required prior to furnacing.

ASHRAE
American Society of Heating, Refrigeration and Airconditioning Engineers.

Aspect Ratio
The ratio of the longer side of a panel to its shorter side.

Autoclave
A chamber that employs high pressure and heat to bond glass and an interlayer, and create laminated glass.

Balustrade
The system of railings and balusters that prevents people from falling over the edge.

Bead
A strip of timber, aluminium or other suitable material secured to the rebate to retain the glass in place.

Bevel
A ground and polished edge to a sloped angle, which gives a decorative appearance to the glass.

Blisters
A profusion of bubbles or gaseous inclusions in the glass. Small bubbles less than 2mm in diameter are referred to as seeds.

Body Tinted Glass
Glass produced by the addition of metal oxides to the molten glass which effect the colour and solar energy transmission properties of the glass.

Bow
A curve, bend or other deviation from flatness in glass.

Breather Tube Units
An IGU with a factory-placed tube in the unit cavity to accommodate pressure differences encountered 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 IGU’s caused by the light refraction from identical thicknesses of glass.

Butt Glazing
The installation of glass panels where the vertical edges are glazed with silicone and without structural supporting mullions.

Cast In Place (CIP) Lamination
Lamination process where the interlayer is a liquid poured between the glass and then chemically cured to produce the final product.

Channel Glazing
A three sided, U shaped opening in a sash or frame to accommodate a glass panel. Beads may be fixed or removable.

Chip
A small shallow piece of glass which has become detached from the original glass edge.

CNC Processing
Computer Numeric Control. This type of machinery enables precision processing of sophisticated shapes, holes and cut outs in glass.

Condensation
The appearance of moisture on the surface of the glass caused by warm moist air coming into contact with the colder surface of the glass.

Countersunk Hole
A hole which has been ground out at the surface to receive a mechanical fixing, allowing for bolting or fixing of the glass panel.

Cullet
Broken glass. It can be the excess from previous glass manufacture or edge trims off the cutting of glass to size. It is an essential ingredient in the pre-melt raw glass mix as it facilitates the melting process.

Curtain Wall
Non-load bearing wall of metal sections, glass and infill panels. It is extensively used in high rise buildings.

Cut Out
The removal of a section from a glass panel.

Daylight Size
The clear unsupported opening size that admits light.

Deflection
The amount of bending movement of the centre of a glass panel perpendicular to the plane of the glass surface under an applied load.

Delamination
A condition in which one or more of the glass panes of laminated glass losses the bond with the interlayer.

Desiccant
A pure molecular sieve or silica gel-based product, the desiccant is placed within the cavity spacer bar of an IGU in order to rehydrate or to remove any residual moisture in the unit.

Design Pressure
Specified pressure a product is designed to withstand.

Direct Transmission
The portion of the sun’s emitted solar heat energy, which is directly transmitted through the glazing.

Distortion
Alteration of viewed images caused by variations in glass flatness and is an inherent characteristic of glass that has been heat treated.

Double Glazing
Two panes of glass separated by a cavity and hermetically sealed in a factory, to provide thermal and/or acoustic insulation.

Dry Glazing
The various means of glazing or sealing in single glass or IGU’s in the supporting frame without wet sealants using pre-formed and extruded materials such as gaskets and wedges.

Edge Clearance
The distance between the edge of the glass and the rebate.

Edge Cover
The distance between the edge of the glass and the sight line.

Emissivity
The measure of a surface’s ability to emit long-wave infra-red radiation.

Faceted Glazing
Glazing with vertical strips of glass joined at the vertical edges with silicone joins to typically form a radius window.

Fenestration
Any glass panel, window, door, curtain wall, or skylight unit on the exterior of a building.

Finger Slots
The slot produced by processing the glass surface by grinding a slot for use as a finger grip in sliding the glass panels.

Fins
Supporting glass panels incorporated into the design of glass facades installed at 90° angle to the glazed surface.

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

Georgian Wired Glass
Glass with an incorporated wire mesh. The glass may be cast or clear polished.

Glazing
The securing of glass in prepared openings.

Hard Coat
Coating applied to the glass during its manufacture whereby it is fused to the glass surface to form a pyrolytic coating. It is very durable and can be cut and toughened from stock.

Heat Strengthened Glass
Glass that has been heat treated to specific surface and/or edge compression range. It is approximately twice as strong as annealed glass at the same thickness. It is not considered a safety glass.

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 when one end is inserted in a fire; Convection – in which actual movement of the medium, gas or liquid 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 from the sun to the earth.

Hermetically Sealed
Made airtight by fusion or sealing.

Insulating Glass
A glazing unit that is made up of two or three individual panes of glass separated by an air space.

Insulated Glazing Unit
A glazing unit that is made up of two or three individual panes of glass separated by an air space.

Interlayer
Plastic material used between two or more glass panels in the manufacture of laminated glass. The interlayer bonds the glass together.

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

Laminated Glass
Two or more pieces of glass permanently bonded together with one or more interlayers.

Light Transmission
The amount of visible light transmission through a type of glass, usually expressed as a percentage.

Lite
A pane or sheet of glass, this term is commonly used in the USA.

Louvre
A window unit comprising of a series of blades of glass or other material lapping over each other when in the closed position.

Low Emissivity (Low E)
Glass with a special thin layer 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 still providing thermal insulation.

Low Iron Glass
Glass which is very low in iron content, and subsequently is extremely white and clear. It transmits an exceptionally high percentage of visible light.

Luminous Efficacy (Light to Shading Coefficient Ratio)
The visible transmittance of a glazing system is divided by the shading coefficient. 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. Also referred to as coolness factor.

Manifestation
Making glass visible, the marking of glass so as to minimize the potential for human impact and injury.

Monolithic Glass
A single piece of glass as opposed to laminated glass or an IGU.

Mullion
A vertical intermediate framing member. When used in curtain walls it represents vertical members.

Mirror Glass
Silvered on one side producing a highly reflective surface.

Nickel Sulphide Inclusions
Minute particles of nickel and sulphide present in the raw material of glass, which under heat such as toughening, form into crystals and in rare cases can cause spontaneous breakage.

Nominal Thickness
The commonly used dimension by which the thickness of a panel is sold and marketed. Please note, the actual thickness of a particular panel of glass may not coincide with the nominal thickness and be subject to the manufacturers tolerances.

Opacifier
Applied polyester film or coating to the surface of tinted or reflective glass rendering it opaque. Suitable for spandrel and non-vision areas.

Orange Peel Effect
A rough surface texture on paint or ceramic ink coating, having the appearance of orange peel and is regarded as undesirable when viewed against light.

Patterned Glass
Glass having a pattern impressed on one or both sides. Used extensively for diffusing light and offering privacy, such as bathroom windows and showerscreens. Can also be referred to as Rolled, Figured or Obscure glass.

Polysulphide Sealant
Polysulphide liquid polymer sealants. They can be converted to rubbers at room temperature without shrinkage upon adding a curing agent.

Polyvinyl Butyral Interlayer
A extremely tough resilient film used to bond glass together during the laminating process. Common thicknesses are 0.38mm, 0.76mm, & 1.52mm.

Pyrolytic
The coating on a glass substrate which is deposited online during the glass manufacturing process. The coating is fired into the glass surface at 700°C and is therefore extremely hard and durable.

Rebate
The part of a frame in joinery which is designed to receive glass which can be face putty glazed or receive a removable glazing bead to hold the panel in place.

Reflective Glass
Glass with a metallic coating to reduce solar heat gain.

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-value). The value is expressed in (W/m2). The lower the relative heat gain, the more the glass product restricts heat gain.

Roller Wave Distortion
Waviness imparted to horizontal heat treated glass which the glass is transported through the furnace on a roller conveyor. The waves produce a distortion when the glass is viewed in reflection.

R Value
The thermal resistance of a glazing system. The higher the R value, the less heat is transmitted through the glazing material. The R value is the reciprocal of the U value.

Sandblasted Finish
A surface treatment for glass obtained by spraying the glass with hard particles to roughen one or both surfaces of the glass.

Safety Glass
Processed glass types which satisfy the requirements of AS/NZS 2208 for safety glazing. Laminated and toughened glasses are Grade A, Wired glass is Grade B.

Salt Spray Test
Accelerated corrosion test in which samples are exposed to a fine mist of salt water. There are primarily used to test silvered glass.

Sash
The moveable window frame which contains the glass panel.

Seeds
Minute bubbles in float glass.

Security Glass
Glass designed not just to meet Grade A safety, but to also withstand vicious attacks. They are specific make ups to resist various gun types, bombs, windows in vehicles etc.

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.

Shading Coefficient
Ratio of solar heat gain through a specific glass product compared to the solar heat gain through 3mm clear glass.

Shark’s Teeth
Serrated features in the cut edges of glass, extending from the score mark through part or all of the thickness. Shark’s teeth seriously weaken the edge and create thermal shock risk.

Shell
Similar to a chip, but often larger and occurring on the face opposite to the score mark.

Shelf Life
Used in the glazing and sealant industry to refer to the length of time a product may be stored before beginning to loose its effectiveness. Manufacturers generally state the shelf life and the necessary storage conditions on the package.

Silkscreen
A decorating process in which a design is printed on glass through a fine silk mesh or similar screen.

Sill
The bottom horizontal member of the window or door frame.

Slumped Glass
Glass that has been heat treated to mould patterns or designs into the surface of the 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 offline, and is often referred to as sputter coating. This 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.

Solar Energy Reflectance
The percentage of solar energy within the solar spectrum that is reflected from the glass surface.

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
The ratio of directly transmitted and absorbed solar energy that enters into the buildings 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 converted.

Spacer
The component of an insulating glass unit which separates the glass and includes a desiccant, with an additional sealant material to prevent air and water penetration.

Spandrel
The panel(s) of a wall located between vision areas of windows, which conceal structural columns, floors and shear walls.

Spectrally Selective
Tinted and/or coated glass that selectively reduces the amount of ultra-violet and infra-red transmittance.

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.

Stones
Any crystalline inclusion embedded in the glass

Stress (residual)
Any condition of tension or compression existing within the glass, caused by incomplete annealing or induced temperature gradient during the manufacture of heat treated glass.

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.

Substance
Refers to the thickness of glass expressed in millimeters.

Substrate
A base material to which other materials are applied.

Surface Compression
The compressive stresses built into the glass surface. A balancing force to centre tension in the glass.

Temper (Toughen)
Inducing predictable residual stresses in the glass by controlled chilling from near the softening point to below the strain point. These residual stresses are in compressive form on the surface of the glass and tensile in the interior. The compressive stress on the surface strengthens the 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 through the thickness of the glass. Typical tints include shades of grey, blue, green and bronze.

Thermal Safety Assessment
A method of assessing the risk of glass breakage from thermal stresses which may be present from location and environmental factors.

Thermal Stress
Stress generate in glasses as a consequence of temperature differentials such as hot centre and cold edges (in the frame).

Thermally Broken
An insulating material of low thermal conductivity placed between materials of high thermal conductivity within a system or extrusion to inhibit the flow of cold or heat.

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 4-5 times stronger than annealed glass of the same thickness when exposed to uniform static pressure loads. Also referred to as tempered glass.

U Value
The measure of air-to-air heat transmittance (loss or gain) due to thermal conductance and the difference in indoor and outdoor temperatures. As the U value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U value, the better the insulation.

Vents
Small cracks at the edges of glass that can lead to breakage.

Vinyl Back Mirror
Organic vinyl backing applied to mirrors that holds the glass together when broken.

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

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

Warp
The easily seen deviation, undulation or twist from the pure plane of the surface of the panel of glass.

Weather Seal
A material included in window and door construction to reduce the air infiltration or improve water penetration resistance of the unit. Also known as sealant joint between the panes of glass.

WERS
Windows Energy Rating Scheme

WHP Laminate
An automotive quality laminate with high penetration resistance and high light transmittance.

Wired Glass
Having a layer of meshed or standard wire embedded near to the centre of the thickness of the panel. This glass is available as polished glass (one or both sides) and as patterned glass.

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