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Glass and Glazing Federation
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Glass Glossary


Argon
An inert, nontoxic gas used to fill insulating units, thus improving thermal performance.

Acid Etching
A process, manly used for glass decoration, where the glass surface is treated with hydrofluoric acid. Acid-etched glass has a distinctive, uniformly smooth and satin-like appearance.

Anneal
A process used to cool formed glass at controlled temperature rates to prevent thermal stresses.

Annealed Glass
During the float glass process, the hot glass is gently cooled in the "annealing lehr", which releases any internal stresses from the glass to enable the cutting and further processing of the glass post manufacture.

Annealing Range
Determines the limits of temperature within which glass may be annealed.

Antique glass
A general term describing a very old piece of glass, perhaps even several centuries old.

Arrised Edge
A basic form of edge working, by removing the sharp edges of cut panes of glass.

Attenuation
Reduction of the intesity of sound as a result of energy conversion from sound to motion or heat.

Acoustic Insulation
The ratio of external sounds passing through a glazing surface.


Antique mirror
Is a decorative silvered glass mostly used for interiors.

Anti-reflective glass
Anti-reflective glass is float glass with a specially-designed coating which reflects a very low % of light. It offers maximum transparency and optical clarity, allowing optimum viewing through the glass at all times.

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

B.T.U.
British Thermal Unit

Bead or Glazing Bead
A strip of wood, metal or other suitable material attached to the rebate to retain the glass.

Bevelling
The process by which an edge of glass is finished to a bevel angle.

Blibe
A cavity which is larger than seed and filled with gas.

Bond Breaker
A substance to which the sealant will not stick.

Brilliant Cutting
Abrasive and polishing wheels are used on flat glass to obtain a decorative effect.

Butyl
A synthetic rubber mostly used for the production of insulating glass units.

Ball Gatherer
A special machine designed to collect a defined quantity of molten glass from the glass furnace.

Bent glass
Bent glass is a normal glass, which is curved with a special process.

Bending
A process used to produce bent glass in which a plate of glass is placed in a horizontal mould and then slowly heated at approximately 600

Blowpipe
An iron or steel pipe for blowing glass.

Bullet Resist Glass
Designed and produced to resist penetration by bullets.

Body-tinted glass
Tranparent float glass with a consistent colour throughout its depth.

Bevel
A decorative form of edge working.

Bow
A form of distortion in toughened and heat strengthened glass, inherent to the manufacturing process.

Blast-resistance glass
The ability of glass to stand blast pressure from an explosion
 
Condensation
When water vapour from the air comes into contact with cold surfaces, the vapour condenses on the cooler surface of the glass forming a foggy effect.

Convection
A transfer of heat by movement of air.

Came
A narrow flat bar of lead, zinc or copper, which holds together the pieces of glass in copperlight glazing or leaded lights.

Caulk
A term used to describe a void filled with sealant.

Clear Glass
Mostly composed of soda, lime and silica to obtain a very clear type of glass.

Compound
A substance formed from two or more elements chemically united in fixed proportions.

Conduction
The transmission of heat through, along or from glass to another material in contact with it.

Cullet
Recycled glass used in the manufacture of clear float glass.

Cutting
A process in which glass is trimmed, also for decorative purposes.


Cold End
A term which describes operation performed on glass when it is already formed and cooled, such as cutting, grinding, acid etching, engraving, etc.

CNC
Stands for computer numerical control.

Coating
A thin layer or covering which changes the basic composition of glass.

Cavity
The cavity formed by the spacer bar between the two panes of glass in double-glazed units. It is generally filled with air.
 
Desiccant
A hygroscopic substance used as a drying agent in insulating glass units.

Dewpoint
A calculated temperature at which water vapor will condense.

Double glazing
Two panes of glass enclosing a hermetically-sealed air space.

Distortion
An optical effect obtained on the glazing surface.

Double Glazed Units
Two panes of glass enclosing a hermetically-sealed air space.

Design Heat Loss
The calculated ratio for heat which is transmitted from a warm interior to a cold exterior.

Dry Glazing
A glazing process which does not use chemical compounds, only dry, mechanical fixings.

dB
A unit of sound measurement.

Deflection
The term applied to the physical displacement of glass from its original position under load.

Dual sealed system
A primary seal of polyisobutylene and a secondary seal of polysulphide, polyurethane or silicone ensuring the effective and durable sealing of double-glazed units.
 
 Edge Cover
The distance of the edge of the glass and sight line.

Edge-polished
A glass finishing process of polishing edges.

Edgework
A process consisting of polishing or abrading-scraping the edge of the glazing surface.

Elastomer
A natural or synthetic elastic rubber or rubber-like plastic

Expansion Tape
A special material used to protect the edges of glass from rigid contact with non-resilient material.

Etching
A process of acid etching one side of float glass to obtain a distinctive, uniformly smooth and satin-like appearance.

Engraved or Engraving
The process of cutting a design, etc. on an annealed glass..

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

Emissivity
Is the relative ability of a surface to absorb and emit energy in the form of radiation.
 
Fogging
A reaction caused by glass condensation.

Frame
The basic rigid supporting structure of a window, building, etc.

Float Glass
A term for perfectly flat, clear glass (basic product). The term "float" glass derives from the production method, introduced in the UK by Sir Alastair Pilkington in the late 1950's, by which 90% of today's flat glass is manufactured.

Furnace Cast
Transfer hot glass from a furnace into a mold.

Fusing
Melting together two or more pieces of glass.

Finishing
Final step in glass processing.

Fenestration
A term used to describe the placement of a window in a structure.

Fire-resistant glass
Special type of glass designed to contains flames and inflammable gas for a longer period.

Fire-resistant glass Integrity
Contains flames and inflammable gas for a short period of time, but does not prevent the transmission of heat to the other side of the glazing(example: wired glass, reinforced laminated glass).

Fire-resistant glass Insulation
Contains flames and inflammable gas for a longer period of time and prevents not only the transmission of flames and smoke but also of heat to the other side of glazing.
 
Gas fill
A process in which argon or krypton is filled into the cavity of insulating glass to improve thermal performance.

Glazing
Glass used as a covering.

Glazing bead
A strip of wood, metal or other suitable material attached to the glazing surround to fix the position of glass.

Gaskets
Pre-formed glazing materials used for bedding or securing glass and for separating glass from the frame.

Glazing Compound
Soft material used for the glazing of glass.

Glass
Hard, transparent, translucent, or shiny substance, made by melting a mixture of sand, soda and lime at a high temperature, followed by cooling.

Glass Staining
Staining is caused by a chemical change or degradation of the glass surface.
Heat gain
Solar radiant heat, transmitted or emitted by glazing into a building, contributing to the build-up of heat.

Heat loss
Heat transfer from internal spaces to external areas through conduction or convection.

Hydrofluoric Acid
A highly corrosive acid which dissolves glass.

Insulating glass
Insulating glass is a multi-glass combination consisting of two or more panes enclosing a hermetically-sealed air space.

Insulating value
See U-value

Insulating Strip
A material used to protect the edges of the glass from rigid contact with non-resilient material.

Insulating Unit
American terminology for Insulating glass.

Infiltration
Amount of air leakage into a building.

Interlayer
The term applied to the material used in laminated glass to bond the glass leaves together.

Inner pane
The pane of a double-glazed unit which faces the interior of a building.
Krypton
A gas used in insulating glass to improve thermal performance of the unit.

Kiln
A furnace or oven for fusing, enameling and casting glass.

K-value
The former term for U-value on the European continent.
Light-to-solar-gain ratio
The ability of glass to permit sunlight to pass without excessive solar heat gain.

Low-conductance spacers
See "Warm edge spacers"

Low-e glass
Low-emission glass (Low-E) is a clear glass, it has a microscopically-thin coating of metal oxide. This allows the sun's heat and light to pass trough the glass into the building. At the same time it blocks heat from leaving the room, reducing heat loss considerably.

Laminated glass
Laminated glass is a combination of two or more glass sheets with one or more interlayers of plastic (PVB) or resin. In case of breakage, the interlayer holds the fragments together and continues to provide resistance to the passage of persons or objects.

Liquid crystal glazing
This is laminated glass, with a minimum of two clear or colored sheets of glass and a liquid crystal film, assembled between at least two plastic interlayers. In the OFF state, the liquid crystals are not aligned, which prevents vision, yet allows light to pass through the glass. When is it switched ON, the liquid crystals align, turning the glass transparent and allowing vision through the glass.

Lite of glass
A single piece of glass, regardless of thickness.

Lehr
The annealing chamber on a float glass manufacturing line where the molten glass is subjected to controlled cooling to obtain annealed glass, free from internal stresses, which can then be cut or worked.
Mastic
Any of a wide variety of waterproof materials, not limited to sealants.

Mirror Silvering
A chemical process used in the manufacture of mirrors, whereby a coating of metal, mostly silver, is deposit on the surface of clear or body-tinted glass.

Multiple Glazed Units
Glazed unit composed of several glass panes separated by spacers and filled with dehydrated air or gas..

Mold or Mould
A hollow container into which molten glass is blown to obtain the desired shape and size.

Mold Blown
Glass which was formed by being blown into a mold.

Motif
Used to describe the design, perhaps recurrent, on glass.

Mirror
Mirrors are commonly made using glass with a smooth, polished surface that forms images through the reflection of rays and light.

Mullion
A vertical framing section between glass panes.
Nickel sulphide inclusion
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.

Non-insulating glass
Fire resisting glass, providing the criteria of E (integrity) only.
Obscure Glass
Any type of glass with uneven surfaces which offers light diffusion and privacy.

On-line coatings
The process in which coatings are directly applied to the glass during production while the glass is still hot in the annealing lehr.

Off-line coatings
In this process a coating is applied under a vacuum to finished cold glass.

Outer pane
The pane of double-glazed unit which faces the exterior of a building.

Opacified
Glass which has been fully enamelled or painted on one side to make it non-transparent.
 
Pane
A lite/sheet of glass.

Plate Glass
Used in the past to produce higher quality glass, this technology was completely outperformed by the float glass process.

Patterned glass
Patterned glass presents uneven surfaces with different impressed patterns.

Photovoltaic glass
A special glass with integrated solar cells, used to convert solar energy into electricity.

Passive coating materials
The properties of passive coating materials do not change with external stimuli.

Patent glazing
A non-load bearing, drained and ventilated framing system, used predominantly in overhead glazing.

PVB
The plastic interlayer incorporated into laminated glass in order to ensure good adhesion and the mechanical and safety breakage characteristic of the glass.

Primary seal
A butyl-based sealant applied to the edges of the space bar during assembly into double-glazed units, to ensure a watertight and airtight seal around the perimeter of the unit.

Rolled Glass
This describes glass is made through a rolling process, whereby the semi-molten glass is squeezed between metal rollers to produce a ribbon with pre-defined thicknesses and patterned surfaces. This process is used for patterned figure and cast glass production.


Rebate
The section of the frame surround which forms an angle into which the glass is placed and held.

Reflective Glass
This is an ordinary float glass with a metallic coating to reduce solar heat. This produces a mirror effect, and is mainly used in building fa

Resin laminate
Two or more sheets of glass assembled with one or more resin interlayers.

Short-wave infrared radiation
Invisible radiation emitted by the sun and other hot objects.

Solar heat gain coefficient (SHGC)
A numerical expression between 0 and 1 expressing the performance of glass in transferring heat.

Solar radiation
The total energy radiating from the sun.


Single glazing
Window or door with a single glass lite.

Safety Glass
Glass which must have passed an impact test and either must not break or must break safely.

Sandblasting
A special glass treatment in which sand is sprayed at high velocities over the surface of the glass.

Sealant
A flexible material for sealing.

Sealed Double Glazed Unit
A combination consisting of two glass panes enclosing a hermetically-sealed air space.

Sealed Multiple Glazing Unit
A combination consisting of several glass panes enclosing a hermetically-sealed air spaces.

Sealer
A substance applied to glass and frame surfaces that guarantees consistent adhesion.

Sheet Glass
A lite of glass.

Silicone
A polymeric organic compound offering excellent resistance to cold, heat and water.

Surface Coatings
A thin layer or covering which changes the basic composition of glass.

Solar Heat Gain
The amount of heat that a structure gains through the glazing surface.

Sputtering
Is a method better known as "vacuuming" to apply coating on the glass.

Structural sealant glazing
An external glazing system where the glass is bonded to a carrier frame without mechanical means.

Screen printed glass
Screen printed glass is tempered or heat-strengthened glass, one face of which is covered, either partially or totally, with mineral pigments.

Secondary seal
A sealant applied to the edges of double-glazed units after the primary seal, to provide effective and durable adhesion between the glass components and spacer bar.

Sight size
The actual size of the opening that admits daylight.

Snow load
An imposed load exerted onto a structure by formation of snow.

Space bar
Generally an aluminum bar along all edges of a double-glazed unit, filled with desiccant, which separates the twoo panes of glass and creates a cavity.

Spall
Small fragments of glass that are ejected from the surface of a laminated glass sheet when the opposite surface is impacted.

Self cleaning glass
This type of glass is covered by a special coating which literally cleans itself.
 
Tempered glass
Tempered (toughened) glass is two or more times stronger than annealed glass. When broken, it shatters into many small fragments, thus preventing major injuries.

Thermal break
A type of metal frame that incorporates an insolating material of low thermal conductivity located between the inner and outer parts of the frame in order to reduce the rate of heat loss.

Transmittance
Ratio of light or heat that can pass through the glazing surface.

Triple glazing
Three panes of glass enclosing two hermetically-sealed air spaces.

Thermal expansion
Change of material size as a result of temperature change.

Toughened Glass
Toughened glass is two or more times stronger than annealed glass. When broken, it shatters into many small fragments which prevent major injuries.

Transparent
Clear, permitting vision.

Translucent
Allowing light to pass through diffusely.

Thermal shock
When glass is exposed to high temperatures, it absorbs heat and expands. At the same time, its edges remain cooler, causing thermal stress.

Thermally insulting glazing
Double-glazed units provide thermal insulation.

Transom
A horizontal framing bar between glass panes.

Tinted glass
See "Body tinted glass"

Tight size
The actual size of an opening into which glass is to be glazed and is measured from the rebate platform.

Tinted interlayer
A colored plastic or resin sheet between two or more panes of glass.
U-factor (U-value)
This is a measure of the rate of heat loss of a building component. It is expressed as watts per square metre, per degre Kelvin, W/m2K.

UV transmittance
Determines the percentage of solar energy in the form of ultra-violet radiation transmitted by glazing.

UDL
Stands for uniformly distributed load.

U-value
A measure of the rate of heat loss of a building component.
Venetian Glass
A thin and fragile glass produced on the island Murano in Italy.

Weatherstrip
A piece of material used on windows or doors to reduce leaks and prevent rain and wind from entering the structure.

Weathertight
Hermetically-sealed to prevent entry of water and air into the structure.

Weathering
The action of water on exposed materials - glass.

Wind Pressure
The amount of pressure produced by wind velocity on the glazing surface.

Waterjet cutting technology
This system consists of high pressure (60.000 psi) water, mixed with abrasives, that passes through a gauge orifice at three times the speed of sound. Such pressure produces a pure working power able to cut any shape of glass or other materials

Wind load
The pressure acting on an external surface of a building caused by the direct action of the wind.

Wired glass
A product in which a wire mesh has been inserted during production. It has an impact resistance similar to that of normal glass, but in case of breakage, the mesh retains the pieces of glass.