Glossary

Absorptance / Absorption
Proportion of incident solar radiation absorbed by the glass. Absorptance is expressed as a fraction, absorption is expressed as a percentage.

Acid etching
Process whereby the polished surface of glass is etched by exposure to hydrofluoric acid to produce patterns, designs or obscuration. For more information, see Pilkington Optifloat™ Opal.

Acoustic laminate
Laminated glass with special interlayers with better acoustic performance than ordinary laminated glass. For more information, see Pilkington Optiphon™.

Acoustic performance / Noise control
Expression of how much a particular product reduces transmitted noise. It is measured by the reduction or attenuation of sound, at specific pitches or frequencies, in decibels (dB).

Activ
Pilkington Activ™ is the brand name for the world’s first self-cleaning glass.

A frame
Rack or stillage for storing glass that is A shaped in profile.

Air mass 1 / Air Mass 1.5 / Air Mass 2
Particular definitions of the solar spectrum (see also relative spectral distribution).

Air gap / Airspace
Alternative terms for the cavity in an insulating glass unit.  These terms are less commonly used now that these cavities are often filled with inert gases such as Argon or Krypton to improve thermal insulation.

Annealed glass
Another term for "ordinary" glass, most commonly used for float glass. Glass that immediately after it has solidified into the required form, while still at a high temperature, is slowly cooled in order to minimise the internal stresses in the glass. The resulting glass can be cut by scoring and snapping and worked. Annealed glass is not usually classifiable as a safety glass.

Anti-bandit glazing
Form of security glazing resistant to manual attack.

Antisun
Discontinued brand name for our range of body-tinted float glasses, replaced by products such as Pilkington Arctic Blue™. For more information, see High Performance Tints.

Applied bevel
Bevelled glass that is stuck on to another piece of glass or insulating glass unit with a UV curing resin.

Applied film / Film
Organic (plastic) film stuck onto glass to give it additional properties, such as safety or security.

Applied leading
Strips of lead adhered to both surfaces of a pane of glass to give the appearance of an historic window.

Arctic
Design of one of the glasses in the Pilkington Texture Glass range.

Arctic Blue
Pilkington Arctic Blue™ is a unique blue body-tinted float glass with improved solar performance compared with traditional tinted glasses.

Armourclad
Discontinued brand name used for spandrel panels.

Armourfloat / Armourlight / Armourplate 
Discontinued brand names used for toughened or heat strengthened glasses.

Armourscreen
Discontinued brand name for screen printed glass.

Arrissing / Arrissed edge
Process by which the sharp edges of a piece of glass are removed.

Aspect ratio
Ratio of the long edge of a pane to the short edge.

Attenuation
Reduction of either sound or electromagnetic radiation.

Audioscreen
Discontinued brand name for Pilkington Optiphon™.

Autoclave
Large pressure vessel within which Polyvinylbutyral PVB laminated glass is heated, to bond the layers of glass and PVB together.

Autumn
Design of one of the glasses in the Pilkington Texture Glass range.

Backing paint
Form of opacifier, or a protective coating applied to mirrors.

Balustrade
Term commonly used for a barrier, protecting a drop, which comes to about waist height.

Barrier
Structures designed to either guide the direction of pedestrian traffic or to provide a guarding to the edges of drops.

Base glass
Glass which is subsequently processed, e.g. acid etching, sand blasting or coating.

Bevelling
Decorative process of grinding a portion off the edge of the glass, to form a shallow angled face, which is then polished.

Blast resistance / Explosion resistance
Ability of a particular type of glass to either withstand explosion pressure waves without breaking or to remain in position if broken.

Borosilicate glass
Glass with increased amounts of Boron. This means that the glass melts at a higher temperature than conventional soda lime silicate glass.

Bow
Form of distortion of toughened glass or heat strengthened glass. Bow may vary depending on the glass type/thickness, size, aspect ratio and other factors. It is measured with the glass in the vertical plane and supported at quarter points. The maximum deviation from a straight edge is measured on the concave surface.

BR1
EN1063 classification for bullet resistant glass to withstand .22 Rifle

BR2
EN1063 classification for bullet resistant glass to withstand 9mm Parabellum Handgun = G0

BR3
EN1063 classification for bullet resistant glass to withstand .357 Magnum Handgun = G1

BR4
EN1063 classification for bullet resistant glass to withstand .44 Magnum Handgun = G2

BR5
EN1063 classification for bullet resistant glass to withstand 5.56mm Rifle = R1

BR6
EN1063 classification for bullet resistant glass to withstand 7.62mm Rifle = R2

Brewster’s fringes
Effect like a rainbow visible under certain lighting conditions, produced in an insulating unit when the two panes of glass are almost exactly parallel to each other.

Brilliant cutting
Manufacture of a decorative polished V-shaped notch in the surface of the glass. The notch may be straight or curved.

Brise soleil / Canopy
Partial shading device, usually above a window on the exterior of the building.

Brocade
Design of one of the glasses in the Pilkington Oriel™ range of acid etched decorative glass.

BS#
British Standard #, e.g.BS6262 part 4 is a safety glazing standard.

BS EN #
As European standards are agreed they are adopted as British Standards and so get a BS EN number. BS EN 1063 : 2000 is the bullet resistant standard.

Bubble
Depending on context this could be:
• bubble of air trapped between interlayers in a laminated glass, or
• gas bubble that has become trapped within a piece of glass during manufacture.

Bullet resistance
Ability of a particular type of glass to withstand armed attack using a particular type of weapon not just by stopping the bullets, but also in terms of the spall ejected from the opposite face by the impact. Within Europe, these are classified in accordance with EN1063 (European) standard between BR1 – BR6.

Bushes
Nylon or hard fibre ferrules used round the shanks of bolts in bolted connections, to prevent direct contact between the bolt and the glass. Often used in balustrades and as part of the Pilkington Planar™ System.

Butt joint
Joint between the edges of adjacent panes, filled with adhesive sealant, commonly silicone based.

Canterbury
Design of one of the glasses in the Pilkington Oriel™ range of acid etched decorative glass.

Capping
Depending on context this can be:
• glazing compound that has been applied to protect another material, for example a silicone sealant that is applied to protect an intumescent compound from the weather
•  metal glazing bead in a patent glazing system.

Cast-in-place (CIP)
Type of interlayer used in the manufacture of laminated glass, by pouring a liquid resin between two panes of glass and curing it either chemically or by exposure to UV light.

Cavity
Gap between the panes of an insulating glass unit also know as the airspace.
Ceramic coating
Enamel finish applied to toughened glass to manufacture Pilkington Spandrel Glass.

Chantilly
Design of one of the glasses in the Pilkington Texture Glass range.

Clear float
Untinted glass produced using the Float process, invented by Pilkington, branded as Pilkington Optifloat™ Clear.

Coated glass / Surface coated glass
Base glass to which an inorganic coating has been applied, either on-line (i.e. during the manufacture of the float glass) or a sputtered coating applied off-line.

Coloured film
Decorative applied film stuck on to the glass, usually in conjunction with applied leading to give the appearance of a leaded light.

Condensation
Formation of water droplets on cold surfaces. Condensation is regularly seen on the room surfaces of single glazing, but its incidence is reduced by the use of insulating glass units and particularly those that contain low-e glass.

Conduction
One of the methods of heat transfer through glass or through the gas in the cavity of insulating glass units.

Conduction heat gain
Transfer of heat from outside the building to the inside when the external air temperature is hotter than the internal air temperature.

Convection
One of the methods of heat transfer by the gas in the cavity of an insulating glass unit.

Cotswold
Design of one of the glasses in the Pilkington Texture Glass range.

Critical locations/ Hazardous areas
Areas of a building, e.g. doors, adjacent to doors, or low level glazing, where glazing is most vulnerable to accidental human impact and which may require the use of safety glass.

Cross bar
Support for the lead cames in large traditional leaded lights.

Cullet
Broken glass. Cullet is often mixed with the other raw materials and recycled in glass manufacturing because it takes 50% less energy to melt cullet.

Curtain wall / Curtain walling
Glazing system in which the complete façade is glazed into frames attached to the building structure. The glazing may include both vision areas and spandrel panels.

Curved glass / Bent glass
Glass which has been heated past its softening point and formed into a curved shape, usually by draping the softened glass over or into a mould. The shaped glass is subsequently cooled slowly to form annealed glass or it may be rapidly chilled to form toughened glass.

 

Data protection
Electromagnetic shielding of computers either to prevent scanning of the radio waves emitted by computers or to prevent corruption of data by interference from outside radio or radar sources.

DataStop
Pilkington DataStop™ is the brand name for a range of laminated glass and insulating glass units that have been specifically designed to give increased electromagnetic shielding for computers and offices.

dB / Decibel
Scale used to measure or describe
•  loudness of sound
•  sound insulation and sound reduction indexes
•  attenuation of radar and radio waves.

dBA
Weighted measure of sound that is designed to stimulate that of our ears. The international standard for this measure is called the 'A' Weighting Curve. Measurements made with this facility are, therefore, termed 'A' weighted decibels or, more concisely, dBA, to discriminate from those made in plain dB, which do not depend directly on human reaction.

Deep Flemish
Design of one of the glasses in the Pilkington Texture Glass range, which is no longer manufactured.

Deflection
How much something moves out of true plane when a load is applied. Glass can bend when a load like snow or wind is applied. Deflections can be calculated in advance and the correct glass for the application specified.

Desiccant / Drying agent / Molecular sieve
Chemical drying agent that dries and helps remove any organic vapours from the air or gas trapped inside the cavity of an insulating glass unit.

Diamond leading
Style of leading copying a traditional leaded light.

Diffusing / Diffusion / Light diffusion
Random scattering of the incident light while still allowing transmission. Usually applied to the effects on light of acid etching or sand blasting.

Direct transmittance
Proportion of solar radiation which goes straight through the glass without being absorbed.

Distance pieces
Sections of material used to space the pane of glass away from the rebate in a frame.

Double glazing
Depending on context can mean:
• a replacement window
• secondary sash glazing
• Insulating Glass Units.

Double Glazing Unit / DGU
Alternative name for Insulating Glass Units comprising of two panes of glass.

Double window
Window containing two panes of glass in the same vision area, but which are glazed separately, not formed into an Insulating Glass Unit. It is sometimes described as secondary sash glazing.

Drained and ventilated glazing
Drained glazing where the rebates are deliberately ventilated so that external air circulates around the edge of the glass to assist in keeping the edges dry.

Drained glazing
Glazing system in which any lodged water is channelled out of the rebates.

Driftwood
Discontinued brand name for one of the glasses in the Pilkington Texture Glass range.

Dual seal system
Edge seal of a high performance Insulating Glass Unit, which comprises primary seals between the spacer bar and the panes of glass and a secondary seal between two panes outside the spacer bar. Pilkington Insulight™ units are made with a dual seal system.

 

E
EN 357 (European Standard) classification for integrity only fire resistant glass.

Eclipse
Pilkington Eclipse™ is our brand name for a range of on-line coated solar control glasses.

Eclipse Advantage
Pilkington Eclipse Advantage™ is a range of good solar control performance on-line coated clear or body-tinted glass, with unique colours and low-emissivity properties.

Edge clearance
Distance between the edge of the pane and the frame in which it is glazed. The clearance is required to allow for tolerances, avoid contact between the glass and its framing and, in the case of drained glazing, to give sufficient room for water to drain away.

Edge cover
Amount of glass within the rebate, i.e. covered by glazing bead. This is required to ensure the pane is effectively secured (i.e. a mechanical requirement) and also to ensure the edge seal of an Insulating Glass Unit is protected from the weather.

Edge deletion
When a small amount of coating is removed from the glass prior to manufacture of Insulating Glass Units. This allows adhesives to grip the glass.

Edge seal
Hermetic seal around the edge of an Insulating Glass Unit, designed to limit the rate at which water vapour penetrates into the cavity. The better performing edge seals are usually dual seal systems.

Effective U-value / Energy balance value
Measure of the performance of glass as an energy saving wall construction when its ability to let in useful solar heat gains is combined with its capability for thermal insulation as described by the U-value.

EI
EN 357 classification for fire resistant glasses offering integrity and insulation.

Electromagnetic radiation
Technical expression for all the wavelengths of electrical or magnetic activity. The full spectrum from cosmic and gamma rays with very short wavelength, through X-rays, UV light (generally described as 280 to 380 nanometre (nm) wavelength), visible spectrum (generally described as 380 to 780) and infra-red, to radio waves with very long wavelength.

Electromagnetic shielding / Electromagnetic attenuation
Use of a Faraday Cage to reduce or prevent the passage of the longer wavelengths of electromagnetic radiation, usually at the frequencies of radar and radio waves. The electromagnetic attenuation give by the Faraday Cage is measured in decibels..

Emissivity
Ability of a surface to absorb or emit electromagnetic radiation. In terms of glass, emissivity is only important with respect to long wavelength radiation (in the range 5000 to 5000nm) produced as radiated heat by objects at around room temperature. Glass naturally has a high emissivity. However, when made into low emissivity (low-e) Glass), the glass surface does not absorb the radiated heat, but reflects it back into the room, enhancing the U-value of the glazing. Pilkington K Glass and Pilkington Optitherm™ are examples of low-e glasses.

EN#
European standard #. These are being adopted as British standards and so become BS EN#.

Enamel
Glass-like material, which is melted into the surface of the base glass at high temperatures to form a ceramic coating.

End Cap
Wooden boxes held onto the ends of a pack of glass with metal banding. One of the standard methods of delivery for larger quantities of glass.

Energy Advantage
Pilkington Energy Advantage™ is a pyrolytic on-line coated low-emissivity glass.

Environmental control
Glass or glazing product which is used for particular effect on the environment inside a building. Often used as a euphemism for solar control it could also refer to sound insulation, thermal insulation, and the control of lighting levels or a combination of all of these.

Everglade
Design of one of the glasses in the Pilkington Texture Glass range.

EW
EN 357 classification for partial insulation or reduced heat radiation, fire resistant glass.

External condensation
Condensation forming on the external face (surface 1) of glazing with very low U-values. The effect requires particular combinations of high external humidity, average temperatures and exposure of the glass to clear night sky.

Façade
Face of a building, or the cladding covering it.

Façade element
Part of the façade, such as a window or spandrel panel.

Face clearance
Distance between the glass and the rebate. This is usually filled with a gasket or sealant.

Fanlight
Glazing immediately above the door.

Faraday cage
Complete electrically conducting earthed screen around a volume of space, across which electrical fields, including electromagnetic radiation, cannot pass.

Fin box
Glazing system used at the ends of glass mullions to retain them.

Fire barrier
Element of construction, such as a wall, partition or glazed screen, which gives an appropriate level of fire resistance.

Fire performance / Fire resistance
Length of time an element of construction, such as a wall, partition or glazed screen, continues to give fire resistance when tested under simulated fire conditions.

Fire protection / Fire safety
Action of a fire barrier in containing a fire.

Fire resistant glass
Glass that in an appropriate glazing system, allows the glazed barrier to achieve fire resistance for more than 30 minutes. The fire resistant glass may be a non-insulating glass, i.e. it satisfies only the integrity requirements of EN1350-2 (European Standard) for the time recorded during the test, or it may be fully insulating glass, i.e. it satisfies both the integrity and insulation requirements for the time recorded during the test.

Fired-on transfer
Applied transfer containing ceramic material or enamel, which is melted into the glass surface at high temperature.

Fixing
Depending on the context this may mean either the method of retaining the glass in position on the building, or the action of installing the glass.

Flemish
Design of one of the glasses in the Pilkington Texture Glass range.

Flexible compound
Glazing material or sealant, which remains permanently elastic, such as polysulphide or silicone sealant.

Float glass
Glass which has been manufactured by floating the molten glass on a bed of molten tin until it sets, producing a product with surfaces which are flat and parallel. Pilkington invented this process in the 1950's. The first product became commercially available in 1959.

Florielle
Design of one of the glasses in the Pilkington Texture Glass range.

Flush glazing
Glazing which has no fixings or parts of the glazing system protruding beyond the outer surface (surface 1) of the glass.

Floatliner
Specially adapted lorry for carrying Jumbo sheets of glass on a stillage.

Frail
Rack or frame for supporting or securing glass.

Framed
Supported by a frame along the full length of an edge. Typical descriptions of glazing systems would be four edge framed or two edge framed.

Framing system / Glazing system
Type of material and the design of the frame supporting the glass.

Free path
Distance, which a person can move directly towards a barrier. This is used as a measure of how much energy can be developed by accidental impact in order to determine the appropriate containment level for glass in the barrier.

Free standing glass protective barrier
Balustrade in which the glass performs all the mechanical functions.

Frequency
Rate of vibration of a sound wave in Hz (Hertz), also know as the pitch, or the rate of vibration of electromagnetic radiation, particular radio waves, usually in MHz (Mega Hertz).

Frit
Depending on the context can be:
• raw materials fed into the furnace.
•  alternative name for enamel.
•  screen printed glass patterns.

 

G0 / G1 / G1/S / G2 / G3
Obsolete British Standard specifications for bullet resistance.

Galleria
Pilkington Galleria™ is our brand name for a rolled glass, which is designed for picture framing. The rolled surface diffuses the reflections from the surface of the glass and so enhances the visibility of the picture.

Gaskets
Solid, preformed glazing materials used to separate glass from other parts of the fixing or frame.

Georgian bar
Grid of bars fixed inside an Insulating Glass Unit in order to make it appear from a distance as though the insulating glass unit is composed of smaller panes.

Georgian Wired
Discontinued brand name used for the Pilkington Pyroshield™ 2 range of fire-resistant glasses.

Georgian Wired Cast / G.W.C.
Discontinued brand name used for Pilkington Pyroshield™ 2 Texture.

Georgian Wired Polished / G.W.P.
Discontinued brand name used for Pilkington Pyroshield™ 2 Safety Clear.

Glare
Excessive illumination or excessive contrast between lit and unlit areas, which can cause difficulty with vision.

Glass mullion / Glass fin / Fin
Support for glass panes made entirely from glass or from glass beams splice jointed with metal connectors. Usually fixed at a 90 degree angle as a brace and support.

Glazing
Depending on the context it is either:
• complete element of construction comprising the glass, the glazing materials and the fixing or frame
• glass or glass product itself
•  act of installing the glass or glass product.

Glazing bead / Bead
Common mechanism used to retain glass in a frame.

Glazing compound / Glazing seal
Glazing material, which is soft and pliable, such as putty or silicone sealant and can be used as a gap filler.

Glazing factors
Radiometric properties, i.e. solar properties and optical properties.

Glazing materials
Gaskets, tapes, glazing compounds, bushes, sealants and other items required for the purpose of glazing a glass product.

Glazing platform
Horizontal leg of the rebate in a frame, upon which the glass sits (on setting blocks) when it is glazed.

Glazing spacer
Small separator placed between the glass and frame.

Guarding
Prevention of persons falling, by means of barriers and balustrades.

 

Hard coating
Term for a coating, which is durable, i.e. resistant to abrasion. It is a term usually applied to pyrolytic coatings.

Heat soaking / Heat soaked
Toughened glass, which has been heated for a period of time at moderately high temperatures to reduce the possibility of spontaneous fractures in service.

Heat strengthening/ Heat strengthened
Glass which has been heated past its softening point and chilled rapidly to increase its strength and make it thermally safe, but which breaks like annealed glass.

Heat transfer coefficient
Measure of the rate at which heat can cross a boundary or surface.

Hermetic Seal
Edge seal designed to prevent gas passing. The edge seal of an insulating glass unit is a hermetic seal to minimise the rate at which water vapour can penetrate into the cavity.

Hot box
Device used to measure the U-value of Insulating Glass Units or the overall U-value of windows, including the frame.

Horizontally toughened glass
Glass, which has been toughened in the horizontal position supported on rollers. Most toughened glass is produced by this method.

Hydrofluoric acid / HF
Acid used in glass etching which is the only acid that will attack glass.

IGU / Sealed Unit
Insulating Glass Unit. May also be shown as DGU (Double Glazed Unit) or TGU (Triple Glazed Unit).

Impact performance / Impact resistance / Impact safety
Impact resistance of a safety glass when tested according to EN12600 (European Standard).

Inclined glazing
Glazing which is either horizontal or sloping up to 75 degrees from the horizontal. Glazing within 15 degrees of vertical is defined as vertical glazing.

Infill panel
Depending on the context, this could mean an alternative term for spandrel panel or a panel underneath the handrail of a barrier.

Inner pane / Inner glass /  Inner leaf
Pane on the room side of an Insulating Glass Unit or double window.

Installation
Depending on the context this is either the act of glazing or the finished glazing.

Insulated panel
Spandrel panel with insulation in the form of organic foam or mineral wool attached to the rear face to lower the U-value.

Insulating glass
Fire resistant glass, which gives both integrity and insulation for a specific period of time greater than 30 minutes. The Pilkington Pyrostop™ range of products is insulating glass.

Insulating Glass Unit / IGU
Construction consisting of two or more panes of glass spaced apart with spacer bars to form a cavity between the panes. An edge seal is applied around each cavity to form a hermetic seal, minimising the ingress of the moisture into the cavity. A desiccant is incorporated in the spacer bar to dry up any residual moisture. The air in the cavity can be replaced by another gas to give the unit specific thermal insulation or sound insulation properties.

Insulation
Depending on the context, this may mean either:
• material applied to the back of spandrel panels to increase the thermal insulation of the panels
•  alternative word for thermal insulation
•  length of time that a construction can give fire resistance in relation to the passage of heat.

Insulight
Pilkington Insulight™ is our brand name for high quality, high performance, dual sealed, Insulating Glass Units.

Integrity
Depending on the context, this may mean the ability of the glass to hold together after fracture, or the length of time that a construction can give fire resistance in relation to the passage of flames and smoke.

Interlayer
Material used to separate and bond the plies of glass in laminated glass. The interlayer can be polyvinylbutyral, cast-in-place or intumescent.

Internal applications
Applications where the glass or glazing products are not exposed to weather.

Interstitial condensation
Condensation occurring in narrow gaps, cracks or crevices.

Intumescent
Capable of expanding. In terms of glass and glazing, intumescent means specifically that the material expands with heat.

Intumescent interlayer
Interlayer which intumesces in fire conditions, not only holding the laminated glass together, but also creating an effective barrier to smoke, flames and heat.

ISO range
Part of electromagnetic radiation, which is UV light according to the ISO definition (between 280 and 380nm).

Jumbo / JU
Size of glass supplied, typically  6000 mm x 3210 mm.

Kappafloat
Discontinued brand name used for Pilkington Optitherm™.

K Glass
Pilkington K Glass™ is our long established pyrolytic on-line coated low-emissivity glass

K value
Term used for thermal transmittance. The units of K value are usually W/m2K, although it is sometimes quoted in kcal/hrm2ºC. The latter unit is slightly larger, which may make K values appear smaller. To convert from kcal/hrm2ºC to W/m2K, multiply by 1.163.

 

Laminated glass / Laminate
Produced by combining layers of glass with plastic (PVB) or resin (CIP) interlayers to form sandwiches of material with specific design properties.

Laminated toughened glass
Laminated product made from multiple panes of toughened glass. This is often specified for overhead and structural glazing applications.

Laurel
Design of one of the glasses in the Pilkington Oriel™ range of acid etched decorative glass.

Lead cames
Strips of lead used to hold the individual small panes of glass in position. The lead cames are relatively flexible, so large leaded lights may need additional support from cross bars attached at intervals to the lead cames.

Leaded glass / Leaded light
Glazing which is formed either in the traditional manner using lead cames to fix small panes of glass, or by sticking applied leading on to the surface of a single pane.

Lehr
Term used in float glass manufacturing. The annealing Lehr is the cooling area on a float line.

Lehr End Size / LES
Sheets of glass that are the width of the annealing lehr.

Light reflectance / Light reflection
Proportion of the visible spectrum, which is reflected by the glass. Light reflectance is expressed as a fraction, light reflection is expressed as a percentage, which can be described as low (<=15%) or high (>=15%).

Light shelf
Reflective device (possibly a partial mirror), placed in a position near the upper edge of a window, which redirects light from the sun and sky onto the ceiling or towards the back of the room, in order to improve the natural illumination within the room.

Light transmittance / Light transmission
Proportion of the visible spectrum, which is transmitted by the glass. Light transmittance is expressed as a fraction, light transmission is expressed as a percentage and can be described as low (<=25%), medium (>=25% and <=50%), or high (>=50%).

Lighting conditions
Level of illumination, specifically the illumination on the public side and the private side in relation to one-way vision effects.

Linkon
Design of one of the glasses in the Pilkington Oriel™ range of acid etched decorative glass.

Linseed oil putty
Traditional glazing compound for single glazed timber windows. Linseed oil putty is NOT suitable for Insulating Glass Units or laminated glass.

Location blocks
Small separators placed between the frame and the edge of the glass to maintain the edge clearance between the glass and the frame.

Long wavelength radiation / Long wavelength energy
Part of the electromagnetic spectrum (i.e. from 5000 to 50000nm wavelength), which is produced by objects at around room temperatures. Glass is opaque to this radiation so short wave radiation from the sun is trapped by the glass, giving the green house effect. It is possible to design coatings which are transparent to visible light, but which are highly reflective, i.e. have a low emissivity, to long wavelength radiation.

Long Wavelength Shading Co-efficient / SWSC
Fraction of the absorption released inwards, divided by 0.87.

Low emissivity / Low-e glass
Coated glass that keeps more heat in a building than ordinary glass.

Low level glazing
Glazing which is wholly or partly within the critical location up to 800 mm from finished floor level.

Luxaclair
A discontinued brand name for special blinds fitted inside a Pilkington Insulight™ unit.

 

m2K/W
Unit used to measure thermal resistance, abbreviated to R-value.

Magnetron sputtering
Technical term to describe the process used in off-line coating. This involves passing the glass into a vacuum chamber. Argon gas is then introduced and electrical currents are then passed into a series of special coating beams in the roof of the chamber. The current causes small amounts of metal oxides to "sputter" onto the glass below and form a thin uniform coating.

Manifestation
Making panes of glass, whose presence may not be immediately obvious, easily visible by the application of permanent patterns, logos or other markings, in order that persons should not walk into them without noticing.

Manual attack
Attack using manually held implements or thrown objects, but not firearms.

Marked / Marking
Indicates the performance of the product. The most common marks are those related to safety glass classification, fire performance and to insulating glass unit performance.

Mayflower
Design of one of the glasses in the Pilkington Texture Glass range.

Mean sound reduction index (Rm)
Average of 16 sound insulation values over the frequency range 100-3150Hz.

Metal casement putty
Traditional glazing compound for single glazed steel windows. Metal casement putty is NOT suitable for insulating units or laminated glass.

Microfloat
Pilkington Microfloat™ is an extremely thin (less than 1.6mm), high-grade float glass manufactured to precise standards, used in a wide variety of applications.

Minster
Design of one of the glasses in the Pilkington Texture Glass range.

Mirage
Discontinued brand name used for Pilkington Mirropane™.

Mirropane
Pilkington Mirropane™ is our one-way vision mirror.

Mirror
Glass which is highly reflective and opaque. Silvering followed by an application of backing paint form the commonest type of mirror.

Mullion
Vertical structure dividing panes of glass in a window or a door. For the horizontal equivalent see transom.

Multi-laminated
Containing more than two plies of glass in the laminate.

Multiple Glazing Unit / MGU
Alternative term for Insulating Glass Unit comprising two or more panes.

Negative Image
Term used in sand blasting and acid etching. It refers to the area of glass that has been eroded by the sand or acid.

Newton's rings
One or more rings of condensation which form when two panes of glass in an Insulating Glass Unit deflect and touch, causing a cold bridge.

Nickel sulphide inclusion
Small impurities that can cause spontaneous fracture of toughened glass some time after toughening.

Non-insulating glass
Fire resistant glass which gives integrity for at least 30 minutes, when glazed in a suitable screen, but which does not give insulation for 30 minutes. For more information see Pilkington Pyroshield™ 2.

Obscuration/ Obscuration level
Classification for Pilkington Texture Glass. Measure of how much you can see through Pilkington Texture Glass. A level 1 pattern is least obscuring, level 5 is most obscuring.

Octaveband
Range of sound frequencies over which the frequency is doubled, e.g. 200 to 400Hz.

Off-line Coating
Coatings applied after glass manufacture.

One-way vision
Optical effect resulting from a difference in light levels which allows vision through a window from only one side. See Pilkington Mirropane™ for more information.

On-line Coating
Coatings applied during glass manufacture.

Opacified
Glass made opaque by the application of a backing paint or other material, a term related closely to spandrel panels.

Optical properties
Light transmittance and light reflectance of glass products.

Optical quality / Visual Quality
Presence or absence of visual distortion or small blemishes in the glass.

Optimirror 
Pilkington Optimirror™ is our brand name for our silvered glass. This product is more environmentally friendly than traditional silvered glass, as there is no copper backing used and no lead in the upper backing paint coat.

Optiphon
Pilkington Optiphon™ is our brand name for our high quality acoustic laminated glass; that offers excellent noise reduction without compromising on light transmittance or impact performance.

OptiView
Pilkington OptiView™ is our range of on-line coated glasses that reduce visible light reflectance when compared with float glass.

Optiwhite
Pilkington Optiwhite™ is our brand name for our float glass with a reduced iron oxide content. This results in a glass that has higher light transmittance and is less green in appearance than standard clear float glass of a similar thickness. Pilkington Optiwhite™ can also be used in solar applications.

Oriel
Pilkington Oriel™ is our brand name for our collection of acid etched decorative glasses.

Outer pane / Outer glass / Outer leaf
Pane on the external side of an Insulating Glass Unit or double window.

Overall U-value
U-value of a window combining the U-value of glass and frame.

Overhead glazing
Sloping or horizontal glazing used in roofs.

P1A / P2A / P3A / P4A / P5A / P6A / P7A / P8A
EN 356 (European Standard) classification for manual attack.

Pack
Bulk quantity of glass, usually between 1 and 3 tonnes in weight often used to describe an end cap. The number of sheets in a pack will depend upon the thickness and size of the glass.

Pallet
Packaging method for transporting and storing glass (see also rack and stillage).

Parry Moon range
Part of electromagnetic radiation, which is UV light according to the Parry Moon definition (between 300 and 400nm). This is a stricter definition of UV light than the ISO range.

Partial insulation
Fire resistant glass that does not achieve 30 minutes insulation as required in EN 13501-2 (European standard) is often referred to as a partial insulation product.

Patent glazing
System of drained glazing incorporating a built-in gutter, commonly used for roof glazing.

Patterned glass / Rolled glass
Manufactured by passing between two rollers, one of which forms an impression or pattern into the glass. For more information see Pilkington Texture Glass.

Pelerine
Design of one of the glasses in the Pilkington Texture Glass range.

Photovoltaic / PV
Producing electricity from light.

Pinhole
Small defect where part of a coating, enamel or backing paint is missing.

Pitch
Frequency of a sound.

Planar
Pilkington Planar™ is our brand name for a range of frameless glazing solutions.

Planarclad
Pilkington Planarclad™ is our brand name for a high performance cladding system incorporating the well known features of the Pilkington Planar™ concept.

Plateau
Pilkington Plateau™ is our  brand name for glass produced to very tight tolerances for use in the cast-acrylic industry. It is available in annealed and toughened forms.

Polarised light
Light waves which are vibrating in a specific orientation, either after passing through a polarising filter, or after being reflected from a surface or from the sky.

Polished edge
Edge of a piece of glass that has been first flat ground and is then polished.

Polished wired glass
Generic name for Pilkington Pyroshield™ 2 Safety Clear. Wired cast glass which has subsequently been ground and polished on both surfaces to make it transparent.

Pyrodur
Pilkington Pyrodur® is our brand name for clear (without wires), partial insulation, fire resistant glass.

Pyroshield 2
Pilkington Pyroshield™ 2 is our brand name for a range of fire resistant glass with a welded steel mesh incorporated. It is an integrity only fire-resistant glass.

Pyrostop
Pilkington Pyrostop® is our brand name for our range of high performance, clear fire resistant glass. The products in this range all give insulation for a minimum of 30 minutes.

Polyvinylbutyral / PVB
Type of interlayer used in the manufacture of laminated glass, by placing a sheet of the material between two panes of glass. This is the most commonly used interlayer.

Positive image
Term used in sand blasting and acid etching. It refers to the area of glass that has not been eroded by the sand or acid.

Private side / Observing side
Side of a one-way vision glass from which the other, public side is clearly visible.

Profile
Term used by window manufacturers to describe bar lengths of PVC window section.

Profilit
Pilkington Profilit™ is a cast glass in U-shape, used in glass wall systems.

Public side / Observed side
Side of a one-way vision glass from which the other, private side is not visible.

Pyrolytic
Applied at high temperature. In relation to glass, this term describes coatings applied on-line when the ribbon of float glass is around 500 to 600ºC. For more information see Pilkington K Glass™ and Pilkington Energy Advantage™.

Quench
Part of a toughening line where glass is cooled rapidly, usually by blowing high pressure cold air at the hot glass.

Radiation
Depending on the context it could mean:
• one of the methods of heat transfer across the cavity of an Insulating Glass Unit
• electromagnetic radiation
• one of the forms in which heat from a fire gets through non-insulating glass.

Radiometric properties
Combined sets of optical properties and solar properties of a glass product.

Rebate
Part of a frame which holds the glass in place.

Rack
Packaging method for transporting and storing glass. See also pallet and stillage.

Ravenna
Design of one of the glasses in the Pilkington Oriel™ range of acid etched decorative glass. 

Reaction to fire / Fire propagation
Way in which a material or product behaves in a fire situation.

Rebate depth
Sum of the edge clearance and the edge cover of the glass.

Reduced heat radiation
EN 13501-2 (European Standard) classification EW for partial insulation fire resistant glass.

Reeded
Discontinued brand name for a design of one of the glasses in the Pilkington Texture Glass range.

Reflectance / Reflection
Proportion of incident light or solar radiation reflected by the glass. Reflectance is expressed as a fraction; reflection is expressed as a percentage.

Reflex
Discontinued brand name for an on-line coated mirror.

Reflite
Brand name for our range of on-line coated medium performance solar control glasses, with low light transmittance and medium light reflectance.

Refraction
Distortion of the path of light as it passes through a glass/air interface.

Relative spectral distribution
Description of the solar spectrum used to determine the radiometric properties of glass.

Rm
The mean sound reduction index.

Robustness
Ability of a pane of glass to resist breakage under accidental human impact.

Roller wave
Visual distortion encountered in horizontally toughened glass.

Rough cast
Discontinued design of one of the glasses in the Pilkington Texture Glass range.

RTRA
Traffic sound reduction index.

R-value
Heat losses are sometimes quantified in terms of thermal resistance, abbreviated to R value. This is the reciprocal of the U-value. R-value = 1/U-value, m2K/W (or ft2hrºF/Btu) this means that a glass with a U-value of 1.9 would have an R-value of 0.53 (1÷ 1.9 = 0.53).

RW
Weighted sound reduction index.

 

Safe breakage
Characteristic of safety glass whereby on impact it either breaks into small fragments (toughened) or is retained within the frame (laminated). 

Safety film / Safety backing
Plastic film adhered to one surface of the glass with the intention of holding it together after fracture.

Safety glass
Glass or glazing product, which conforms to EN 12600 (European Standard) which classifies the product as giving no break or safe breakage when the glass is tested.

Sag bending
Technique for bending glass.

Sand blasting
Process whereby the polished surface of glass is etched by exposure to high-pressure air blown sand or grit, primarily for decorative effect.

SAP
Standard Assessment Procedure. UK Government approved method of determining the energy efficiency of a building. It is measured on a scale of 0–100 with 100 being the most efficient.

Satin
Discontinued brand name for Pilkington Optifloat™ Opal, a translucent decorative rolled glass.

Screen printed glass
Glass which has been given a specific decorative surface finish of either ceramic or epoxy based ink. This product can be used for decorative effect or as a means of glare reduction or solar control.

Sealant
Glazing compound, which sets after application into a rubbery consistency.

Secondary glazing
Second sheet of glass or plastic applied to a window frame, primarily for the purpose of noise reduction, but also offering some thermal insulation benefits.

Secondary processing
Subsequent processing of glass after initial manufacture, e.g. manufacture into laminated glass, toughened glass, insulating glass units or decorative processing.

Security
Depending on the context this means either the ability of glass to withstand manual attack, bullet or blast or electromagnetic shielding.

Secur-VU
Discontinued brand name for a product consisting of a polyurethane frame containing two panes of toughened glass with applied stripes.

Seed
Small bubble trapped within a piece of glass.

Setting blocks
Small packers placed under the bottom edge of the glass to support it off the glazing platform and allow clearance for drainage and ventilation.

SG1 / SG2
EN1063 (European Standard) classifications for bullet resistant glass to withstand shotgun (S86).

Shading Co-efficient/ Total Shading Co-efficient/ TSC
The total shading co-efficient/ TSC is derived by comparing the properties of any glass with a clear float glass having a total energy transmittance of 0.87 (such a glass would have a thickness of about 3mm). It comprises a short wavelength and long wavelength shading co-efficient.

Short Wavelength Shading Co-efficient / SWSC
Direct energy transmittance divided by 0.87.

Shadowlite
Discontinued brand name for a 9% light transmission tinted interlayer.

Shopbond
Discontinued brand name for a system used in shopfronts. This system involves bonding laminated glass into a special reinforced frame, to prevent the glass being removed from the frame.

Shopshield
Discontinued  brand name used to describe laminated glass.

Short wavelength radiation / Short wavelength energy
Part of electromagnetic radiation (i.e. from 280 to 2500nm wavelength), which is radiated by the sun.

Silicone sealant
Type of UV resistant glazing compound made from silicone material which is gunned into position and cures into an elastic solid.

Silvering
Depositing silver on glass to form a mirror. The layer of silver is then protected by a copper backing, which is then protected by a lead based backing paint.

Single glazed
Fitted with only one pane of glass, neither an insulating glass unit nor a double window.

Soda lime silicate glass
Ordinary window glass, including float glass, patterned glass and wired glass.

Solar Control
Effectiveness of glass in limiting solar heat gain. Solar control can be described in terms of the total shading coefficient of the glass, as being low (shading coefficient > 50%), medium (35% < shading coefficient < = 50%), or high (shading coefficient < = 35%).

Solar direct transmittance
Proportion of incidence solar radiation, which passes straight through the glass, expressed as a fraction.

Solar-E
Pilkington Solar-E™ is our range of good solar control performance on-line coated glasses offering low solar heat coefficient gain, low reflectivity, reduced glare and low-emissivity.

Solar gain factors
Numbers related to and derived from shading coefficients, which also describe the ability of the glazing to reduce solar heat gain.

Solar heat gain / Heat gain
Amount of heat from the sun which passes through the glass into a building.

Solar Panels
These fall into two main types; Photovoltaic which convert sunlight to electricity and panels designed to use the sun's solar radiant heat properties to warm water.

Solar properties
Properties of glass related to solar radiation, i.e. reflectance, absorptance, solar direct transmittance, total solar heat transmittance, shading coefficients and solar gain factors. The term is also used occasionally to include emissivities and optical properties.

Solar radiation / Solar Energy
Heat, light and UV light emitted by the sun as received at the surface of the earth.

Solar spectrum
Electromagnetic radiation emitted by the sun and its variation with the wavelength of the radiation. The solar spectrum effectively has a range of wavelengths from 280 to 2500nm, with the largest proportion present as visible light.

Spacia
Pilkington Spacia™ is the world’s first commercially available vacuum glazing.

Spacer
Depending on context can be an alternative term for spacer bar or a glazing spacer.

Spacer bar
Preformed section, usually aluminium or steel, which spaces apart the panes of an insulating glass unit in order to form the cavity. The spacer bar also usually acts as a container for the desiccant in the insulating unit.

Spall
Pieces of glass ejected from one side of a pane of glass when it is impacted from the opposite side. This term is commonly used in connection with bullet resistance, where a requirement for reduced spall (RS) may be part of the classification system.

Spandrel panel
Glass panel, commonly used in a curtain wall, which is made of an enamelled or opacified glass in order to hide parts of a building structure.

Spectral distribution
Proportion of different wavelengths of a spectrum.

Spectrum
Wavelengths contained within a particular type of electromagnetic radiation, such as the solar spectrum.  May also refer to Pilkington Spectrum, our online glass performance modelling tool.

Speech hole
Holes drilled or sand blasted into a piece of glass.

Standard Stock Size / SSS
Size of glass supplied, typically  2500 mm x 1605 mm or smaller.

Stained glass
Depending on the context, this may mean:
• a traditional leaded light made with glass of different colours to form a picture or decorative pattern
• a pane of glass with coloured applied film and applied leading which looks like a traditional leaded light
• a piece of glass of the type used in the leaded light.

Stepped unit
An Insulating Glass Unit with one pane larger than the other. This difference in size may be only one edge (often used on the bottom edge of roof glazing).

Stillage
Packaging method for transporting and sorting glass.

Stippolyte
Design of one of the glasses in the Pilkington Texture Glass range.

Stone
Foreign body in the surface of a piece of glass.

Stress pattern
Effect seen on toughened glass when it is viewed under polarized light or through a polarizing filter.

Structural glass
Glass used in a manner where it may be supporting other building components (e.g. glass mullions) or where it performs a semi-structural role (e.g. free standing glass protective barriers).

Suncool
Pilkington Suncool™ is the brand name for a range of off-line coated, high performance solar control glass.

Sunplus
Pilkington Sunplus™ is an extra clear low iron patterned glass with very high solar transmittance.

SunShade Silver
Pilkington SunShade™ Silver is a medium solar control performance off-line coated glass.

Surface 1
Surface of the glass exposed to the weather.

Surface 2
Room side surface of single glazing, or the cavity surface of the outer glass in an insulating glass unit.

Surface 3
Cavity surface of the inner glass in an insulating glass unit.

Surface 4
Room side surface of double-glazing.

Surface resistances
Inverse of the heat transfer coefficients at a surface.

Surveillance Mirror
Discontinued brand name for Pilkington Mirropane™, our one way vision mirror.

Sycamore
Design of one of the glasses in the Pilkington Texture Glass range.

 

Taffeta
Design of one of the glasses in the Pilkington Texture Glass range.

TEC
Pilkington TEC Glass is an on-line coated glass, which is thermally and electrically conductive, used in a wide range of applications. NSG TEC™ is used within solar applications.

Thermal break
Gap or a portion of low thermal conductivity in a metal frame, separating the inner and outer parts of the frame, designed to increase the thermal insulation of the frame.

Thermal fracture / Thermal breakage
Glass broken by the action of a heat source (e.g. Sun, radiators).

Thermal insulation
Ability to restrict the flow of heat.

Thermal properties
Depending on the context this could mean either  U-value, solar properties or both.

Thermal safety check
Determination of whether annealed glass is thermally safe in a particular scenario. If a glass is not thermally safe it is necessary to use toughened glass instead.

Thermal Stress
Stress developed in glass due to differences in temperature across its surface. Too high a temperature difference can result in thermal fracture.

Thirdoctaveband
Range of sound frequencies that is one third of an octaveband.

Thirdoctaveband centre frequency
Frequency commonly used by sound engineers to ascribe the average loudness or sound insulation over that thirdoctaveband.

Tight size
Size of the opening in frame into which glass is to be glazed. Glass should be smaller than the tight size, to allow suitable edge clearance.

Time/temperature curve
Prescribed temperature rise in a fire test furnace as a function of the duration of the test, usually to EN (European Standard) 1363-1 and ISO 834-1 standards.

Tinted float / Body tinted float  
Float glass that has small amounts of metal oxides added during the melting process to colour it and give it solar control properties.

Tinted interlayer
Coloured interlayer in laminated glass, designed to give either solar control or decorative properties.

Total solar heat transmittance / TSHT / Total solar energy transmittance / Solar Heat Gain Coefficient
Fraction of solar radiation at near normal incidence that is transferred through the glazing by all means. It is composed of the direct transmittance, also known as the short wave component and the part of the absorptance dissipated inwards by longwave radiation and convection, known as the longwave component. The proportions of the absorbed energy that are dissipated either inside or outside depend on the glazing configuration and the external exposure conditions.

Toughened glass / Tempered glass
Glass which has been heated past its softening point and chilled rapidly to build in a surface compressive stress which gives it greatly increased strength and makes it break into small fragments if broken.

Traffic Noise Reduction Index (RTRA), Ctr
Derived by taking into account a typical spectrum of road traffic noise.

Translucent
Letting light through, but obscuring clear vision. for example Pilkington Optifloat™ Opal or Pilkington Profilit™.

Transmittance / Transmission
Proportion of incident light or solar radiation transmitted by the glass. Transmittance is expressed as a fraction; transmission is expressed as a percentage.

Transom
Horizontal bar across an opening. Often used to refer to a window that is attached to the bar.

Ultraviolet transmittance
Proportion of incident UV radiation transmitted by the glass, expressed as a fraction.

U-value / Thermal transmittance / U-factor
Measure of the rate of heat loss through the wall of a building material. U-values depend on several different variable factors, such as wind speed and temperature, so they are usually quoted in relation to a specific set of steady state environmental conditions. U-value is a commonly used term, not specific to glass. Subscripts after the “U” indicate the scope of the rate of heat loss – w refers to a complete window, or g for the glass alone.

UV curing resin
Resin that has to be exposed to UV radiation in order to cure. This sort of resin is used in the manufacture of cast-in-place laminated glass and for sticking decorative features such as applied bevels to glass.

UV filter interlayer / UV filter layer
Interlayer in a laminated glass, which blocks the majority of the UV radiation. For more information see Pilkington Optilam™.

UV radiation / UV light
Part of the electromagnetic spectrum with a slightly shorter wavelength than visible light, within the UV range, known as ultraviolet light or UV light.

UV range
Wavelengths of the electromagnetic spectrum usually described as being UV radiation. There are two common descriptions, the ISO range (280-380 nm) and the Parry Moon range (from 300-400 nm).

UV reduction / UV protection
Proportion of UV radiation which is blocked by the glass.

UV screen
Discontinued brand name for a range of cast-in-place laminated glass which is no longer produced.

UV transmittance / UV transmission
Proportion of incident UV radiation transmitted by the glass. UV transmittance is expressed as a fraction; UV transmission is expressed as a percentage.

Vent hole
Round hole cut into an insulating glass unit for a fan or ventilator.

Vertical glazing
Glazing which is either true vertical or within 15 degrees of true vertical.

Vision area
Depending on the context, either an oval with axis equal to the height and width of the pane, or parts of a building façade or curtain wall which are intended for the passage of light.

Vision panel
Depending on context, either:
• term used to distinguish a part of curtain walling as being distinct from the spandrel panel
• small pane of glass in a door to allow people to look through without necessarily opening the door.

W/m2K
Unit used to measure thermal conductance, usually abbreviated to U-Value.

Warwick
Design of one of the glasses in the Pilkington Texture Glass range.

Weighted sound reduction index (Rw)
The weight sound reduction, in decibels, which incorporates a correction for the ear's response to sound.

Whisperply
Discontinued  brand name for Pilkington Optiphon™.

Wired glass
Generic name which covers both polished wired glass and wired cast glass. Our product range is called Pilkington Pyroshield™ 2.

Wired cast glass
Generic name for Pilkington Pyroshield™ 2 Texture.