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Technical Glossary

Dictionary of most important terms used in Glass Industry


Acid-etched glass

Satin-like, translucent glass manufactured by acid-etching one surface of the glass (see SGG SATINOVO)

Adhesive Glazing / Adhesively Glazed

See “Structural sealant glazing”

Air Filled Cavity

See “Cavity”.


See “Cavity".

Annealed Glass

Glass that does not undergo the process of toughening, lamination or heat strengthening. Also known as 'normal' glass and most commonly used for flat glass. 

Anti-Reflective Glass

Surface-coated glass which minimises light reflectance and appears therefore to show virtually no visual reflection (see SGG VISION-LITE).


A basic form of edgeworking, by removing the sharp edges of cut panes of glass.

Aspect Ratio

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

All-Glass Systems (GGA)

An all-glass system is a construction of several panes of glass (including doors) that are connected without a metal frame. The discs are connected with point holders and thus take on a constructive, supporting function. An example of an all-glass system is constructions made of several fixed glass panes and glass doors, as they are often found in shopping malls.



A barrier or form of guarding, generally waist-height, which protects people from falling where there is a change in floor level, for example stairs and balconies.


A strip of wood, metal or other suitable material attached to the glazing surround to retain the glass.


The glazing material which seals the glass and beads in the rebate. Back bedding is the glazing material between the face of the glass and the rebate upstand after the glass has been pushed into position. Front bedding is the glazing material between the face of the glass and the bead.


A decorative form of edgeworking, where the edges of a glass pane are ground and polished smoothly at an angle.


The ability of a material to withstand blast pressure from an explosion; whether intentional or accidental (see SGG STADIP PROTECT).

Body-Tinted Glass

Transparent float glass with a consistent colour throughout its depth (see SGG PARSOL).

Bolted Glass Assemblies / Assembly Systems

Structural bolted glazing systems incorporating fixed or articulated bolts.


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

British Standards

Codes of Practice offering guidance and recommendations on what is considered current best practice. Applicable to the whole of the UK and in most cases adopted by the Republic of Ireland.


The British Standards Institution.

Building Regulations

Building Control legislation laid down by Acts of Parliament.

Bullet-Resistant Glazing

Security glazing affording a defined resistance against the firing of specified weapons and ammunition (see SGG STADIP PROTECT).

Butt Joint

Joint between edges of adjacent panes, vertical or inclined, and usually weathered with a suitable sealant.

Blown Glass

The shaping of glass by blowing air through a hollow rod into the center of a molten glass gather.



Strip of material which may retain infilling, fitted over a glazing bar to impede direct water penetration.


A sealant applied to fill the gap above a strip glazing material, positioned between the glass and the rebate upstand and/or bead.


The void/space formed by the spacer bar between the two panes of glass in double-glazed units, and nowadays is generally filled with argon for enhanced thermal insulation.

CE Marking

When the European marking is officially in force, any glass product that is used in construction and buildings, which is sold within the European Union, must bear the label. This label can be stamped onto the product, the packaging or the accompanying commercial documents.

Ceramic Frit

See “Enamelled glass”.


A small bevelled edge connecting two surfaces. If the surfaces are at right angles the chamfer will typically be symmetrical at 450, similar in appearance to arrissing.


Computer controlled cutting. Sizes are inputted into a computer and then the glass is cut automatically.

Cold Zones

Areas in close proximity to glazing, especially single-glazing, where exchange of heat by radiation can lead to the sensation of feeling cold or draughts.

Colour Rendering

Term given to the change in appearance of the natural colour of a material/object due to the colouration effect of light being transmitted through or reflected by the glass onto any given surface.


Process whereby gas or vapour turns into liquid by cooling.

Cut Glass

Glass that is decorated by using grinding stones that are worked wet to cut designs onto the glass.


Glass used in guarding situations designed to withstand specified loads and prevent people from falling.

Counter Sunk

A hole drilled through the glass so that when a screw or bolt is inserted the head of the fixing is flush/level with the surface of the pane. The fixing must be isolated from the glass by nylon or soft lining material; there must be no glass-to-metal contact.

Critical Locations

See “Safety critical locations”.

Clear Glass

Transparent glass with an almost colourless and neutral appearance.


Recycled glass used in the manufacture of clear float glass.

Curtain Walling

Non-load bearing, typically aluminium, facade cladding system, forming an integral part of a building’s envelope.

Counting in Decibels

Two acoustic sources of 50 dB each generate a total noise of 53 dB. Doubling the noise source causes its increase by 3 dB. To increase the noise level by 10 dB, the number of noise sources should be increased tenfold. The human ear does not respond to the noise level in a linear manner. Increasing the noise level by 10 dB (ie a tenfold increase in the number of noise sources) is perceived by our ear as its doubling. The consequences of this phenomenon are as follows:

  • the noise reduction by 1 dB is barely audible;
  • reducing the noise level by 3 dB is audible;
  • reducing the noise level by 10 dB by half reduces the feeling of noise

Curved glass

Glass, which is curved in form, produced by heating it to its softening point, so that it takes the shape of the mould. Curved glass was invented as early as the 17th century during the construction of the Versailles Palace. The glass gets its special shape by first heating a glass sheet in an oven to its softening point of 500 ° C to 600 ° C. It lies horizontally on a concave or convex shape and is thus bent into its final shape. After a gradual controlled cooling to avoid stresses in the structure, the glass is polished and stored in a form corresponding to the curvature. Annealed, toughened and laminated glass is available in curved form (see SGG CONTOUR).

Cut-out (Internal and External)

See “Notch”.

Cast Glass

Glass produced by 'casting', by pouring molten glass into a mould or by heating glass already contained in the mould until the glass melts and assumes the shape of the mould.


Calumen is a calculation program for the determination of photometric and radiation-physical values of mono- and insulating glass panes.


Daylight Coefficient

Knowledge of the light transmittance coefficient, which characterizes the glass, allows to determine the approximate level of lighting that we get inside the room, assuming a certain level of lighting outside. The ratio between lighting at a given point in the room and external lighting, measured in the horizontal plane, is unchanged regardless of the time of day. This ratio is called the "daylight coefficient".


The reorientation of daylight by means of systems incorporating reflective and adjustable surfaces or grilles. Daylighting systems re-direct natural light, distributing diffused light in a room space and prevent strong areas of glare (see SGG LUMITOP).


Abbreviation of decibel, the unit of measurement of sound, measured against a logarithmic scale. A-weighted decibels [dB(A)] are "weighted" for the response of the human ear.


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


Generally a pure molecular sieve- or silica gel-based product, the desiccant is placed within the cavity spacer bar of double-glazed units in order to dehydrate or to remove any residual moisture in the unit.

Distance Pieces

Glazing blocks located between glass, rebate upstand and bead to maintain distance, ensure adequate depth of glazing materials and constrain movement of the glass under wind load.

Double Glazing/Double Glazed Unit (DGU)

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


Abbreviation of “Dots Per Inch”- a printing term referring to the resolution of a printed image.

Drained and Ventilated

Frame types which help prevent prolonged contact between the edge seal of double-glazed units and moisture.

Dry Glazed Systems

A term applied to glazing systems that use gaskets to retain the infill material (glass).

Dual Sealed System

A primary seal of polyisobutylene and a secondary seal of polysulphide, polyurethane or silicone ensure the effective and durable seal of double-glazed units.

Dubbed corner

The removal or blunting of sharp corner edges, often done in conjunction with arrissing, again it might be referred to as a chamfered corner.


Logarithmic unit for the sound level.



By processing the glass surface with a solution containing hydrofluoric acid, a dull appearance is created. The so-called satined glass can be used well as a visual screen with good light transmission at the same time.


Symbols which, combined with a period of time, define the classifications for fire resistance:

  1. E - Ability of a glazed material to prevent the spreading of flames or hot gases (integrity)
  2. EI - ability of a glazed material to limit heat transfer to the unexposed surface (integrity and insulation)
  3. EW - ability of a glazed material to reduce the emission of radiated heat or energy and to provide a heat barrier for persons (radiation)

Edge Clearance

The distance between the edge of the glass and rebate.

Edge Cover

The distance of the edge of the glass and sight line.

Edge Seal

See “Dual sealed system”.

Effective U-Value

See “Energy balance”.


Emissivity is a surface characteristic of a material. It is the relative ability of a surface to absorb and emit energy in the form of radiation. Low-emissivity (Low-E) coatings reduce the normally relatively high surface emissivity of the glass. The coatings are mainly transparent over the visible wavelengths but reflect long wave infra-red radiation towards the interior of the building. The result is greatly reduced heat loss (see SGG COOL-LITE K, SK and SGG PLANITHERM).


“European Norms” or standards, which are gradually harmonising with and superseding British Standards.

Enamelled Glass

Opaque glass colors, which are actually glass powders, that are melted onto a glass surface. One face of the glass is enamelled, by applying a ceramic frit that is then fired into the surface of the glass at high temperature. Depending on the cooling regime employed, this then results in either a heat-strengthened or thermally toughened glass (see SGG EMALIT EVOLUTION).

End Cap

Stock glass with wooden packaging on either end to protect it. Commonly used on patterned glass.

Energy Absorptance (A)

The percentage of solar radiant heat energy absorbed and re-emitted externally and internally by the glass.

Energy Balance

The difference between the amount of heat gain and heat loss through glazing. Also known as the “Effective U-value”. The window on one hand is a source of thermal losses, determined by the U-value, and on the other hand it is a source of solar energy reaching the room, resulting from the Solar Factor g. Energy balance is thermal losses reduced by the sun's energy penetrating into the room. The energy balance is negative if the amount of solar energy reaching the room is greater than thermal losses. Thus, in a passive building, we should use windows with the lowest heat transfer coefficient and a relatively high g-value for obtaining solar profits.

Energy Reflectance (RE (external) and RI (internal))

The percentage of solar radiant heat energy reflected by glazing.

Energy Transmittance (T)

The proportion of solar radiant heat energy which is transmitted directly through glass (formerly abbreviated to DT (Direct Transmittance)).

Enhanced thermal insulation

Conventional double glazing provides thermal insulation. Double-glazing comprising a low-emissivity glass provides enhanced thermal insulation.

External Glazing

Glazing in which one or both sides are exposed to the outside.

Edge Processing

By grinding and polishing the sharp cutting edge is finished. The unprocessed glass edge with sharp edges is used only where it is in the frame and thus there is no risk of injury. Functionality and appearance are designed according to the usage.

Enamel Colors

The front of the glass to be enameled is transported on a belt under an enamel-filled container. In this container is a gap through which a constant stream of enamel paint runs. This creates a nationwide enameling. After drying the paint or enamel, the glass is tempered in an oven to toughened safety glass (ESG). By heating, the ceramic silkscreen or enamel colors are burned in and combine permanently mineral with the glass surface. Application: Only for single color, full - surface color design of facades, wall coverings, etc



The front or face of a building.

Fiber Glass

Very fine strands of glass used in the form of glass wool.


The term used to describe the surfaces of the glass in numerical order from the exterior to the interior. The exterior surface is always referred to as face 1. For a double-glazed unit, the surface of the outer pane facing into the cavity is face 2, the surface of the inner pane facing into the cavity is face 3 and the internal surface of the inner pane is face 4. With triple glazing there will be a face 5 and 6, with face 6 becoming the roomside face.

Face Clearance

The distance between the face of the glass, the rebate upstand and upstand face of a bead. Also known as front clearance and back clearance.


Abbreviation for finished floor level.


A vertical support made entirely of glass between two abutting glass panes, sometimes known as a glass mullion.

Finger Pull

Finger pulls are a recess or partial depth slot a few millimetres deep into the body of a pane of glass. The glass is often toughened and usually incorporated into a sliding glass door system in display, kitchen or bathroom cabinets.

Fire Resistance/Fire-Resisting

The ability of a building material to provide an effective barrier against the passage of flames, smoke and toxic gases and/or to reduce the transmittance of radiated heat (see SGG CONTRAFLAM, SGG CONTRAFLAM LITE, SGG SWISSFLAM, SGG SWISSFLAM LITE, SGG CONTRAFLAM STRUCTURE, SGG PYROSWISS, SGG VETROFLAM.


Product which meets the two fire resistance criteria E, EW and EI: flameproof and impervious to hot toxic gases or flammable materials (see above)


Strip of impervious material, usually metal, dressed or fitted in order to exclude water from the junction between a frame and adjacent building elements.

Float Glass

High quality, transparent flat glass manufactured by means of the float tank procedure that is, floating molten glass on a "tin-bath" at extremely high temperature (see SGG PLANILUX).

Float Glass

Produced when molten glass is floated on a bath of molted tin to form a continuous glass ribbon. Also a type of flat glass.


Ground glass, ranging in a variety of sizes from fine powder to gravel-like size. Sometimes used for painting effects and can be fused or cast.

Four Edge Glazing System

Infilling (glass) is supported continuously on all four edges by a suitable framing/glazing system.

Frame Terminology

Below is a typical window frame and the terminology used to describe the various parts/elements:

Free Path

Referred to in BS 6180 relating to guarding and balustrading. It is the unhindered distance a body can travel in a direction perpendicular to the surface of a barrier.

Free Standing Barrier

A structural barrier where the glass is fixed to the structure, either adhesively or by clamping, along its bottom edge and has a continuous handrail attached to the top edge. The glass is designed to withstand all the imposed design loads and there are no balusters.


The rate of vibration of sound waves per second, measured in Hertz.

Full Height Barrier

Where glass forms part or whole of a wall element it is classed as a full height barrier if any part of the glass is below the minimum barrier height, which is usually taken to be 800mm from finished floor level.


The fusion of different coloured glasses at high temperature to attain a collage-effect in glass.


Any area within the building, that lets in light. Includes windows, glass doors, glass block walls and skylights.

Facet Edge

Through several grinding and polishing operations, the edges of the glass (eg the mirror) are bevelled at an angle <90 °.

Flat Glass

A commonly used terminology to indicate sheet glass, float glass and other forms of rolled/plate glass where the shape of the glass is flat.



The g-value (solar factor) is the measure of the solar energy gain of a glass. The value measures the thermal radiation that is introduced through the glass into a room by the solar irradiation. It refers to the wavelength range from 300 nm to 2500 nm. The g-value is the sum of the radiation passing directly through the glass (transmission) and the secondary heat emission through the glass into the interior of the room (absorption).


Pre-formed glazing materials used for bedding or securing glass and to separate the glass from the frame or fixings.


The process of securing glass into provisions made in buildings, especially doors, windows and partitions. It also refers to the collective elements of a building comprising glass, frame and fixings.

Glazing Bead

See “Bead”.

Glazing Materials

The materials required for the glazing of glass products such as glazing compounds, tapes, sealants and gaskets.

Glazing Stop

Fitting attached to the lower end of a glazing bar to prevent the infilling (glass) from sliding/slipping.

Glazing/Glass size

The dimensions of the cut glass ready for installation, clearances having been allowed. As a general rule the industry gives width first and height second (w x h).


The prevention of people falling wherever there is a change in floor level by means of a permanent barrier.


A ball of molten glass taken from a pot or furnace on the end of a hollow blow rod.


Colourless, tinted, transparent or opaque, an inorganic product of fusion cooled without crystallizing. Referred by the name 'monolithic glass'. Hard and brittle with a conchoidal fracture.

Ground Edge

Ground edges denote an edge surface which has been worked over the entire surface by grinding. These edges have a dull appearance.

Glass Production (Float Glass)

In the float glass process, an endless glass ribbon floats from the melting tank onto a liquid tin bath. Due to the surface tension of the molten glass and the flat surface of the tin bath, an absolutely plane-parallel glass ribbon is naturally formed. In the cooling channel and on the subsequent transport section, the glass cools down to room temperature so that it can be cut into sheets.



Top member of a frame, usually horizontal.

Heat Soak Test (HST)

The heat-soak test is a special process (hot storage test), which is carried out after the thermal toughening process in order to reduce the risk of spontaneous breakage of toughened glass in service due to nickel sulphide inclusions (NiS) (see SGG SECURIT HST, SGG SECURIPOINT).

Heat-Formed glass

Glass, which is heat-formed at a very high temperature, see “fusing”.

Heat-Strengthened Glass

Glass which has been heat-treated in order to increase its mechanical strength and resistance to thermal breakage. It has fracture characteristics similar to that of ordinary annealed glass and is not classed as a safety glass (see SGG PLANIDUR).

Heat-Treated/Heat Treatment

A generic term for glass that has been heat-strengthened or thermally toughened in order to increase its mechanical strength and resistance to thermal breakage (see SGG SECURIT / SGG SECURIPOINT).

Heel Bead

A bead of sealant applied between the edge of the glass and the rebate angle.

HIAB Vehicle

Vehicle with lifting equipment attached.

Horizontal Line Load

A linear uniformly distributed load applied horizontally at a given height above finished floor level (e.g. 1100mm). Most often associated with balustrade and guarding applications.

Horizontal Toughening

A thermal toughening process whereby the glass is toughened horizontally and supported by rollers.

Hemmed Edge

The hemmed edges correspond to the dimensions of the cut edge. The edges are broken with a grinding tool, which deprives the edge. This is the lowest form of edge banding.


Impact Performance/Resistance

When related to safety glazing this is the classification of safety glass when tested to BS EN 12600.

Inclined Glazing

Glazing that is inclined at an angle between horizontal and 75° from horizontal.

Infill Panel

The term applied to the glass panel underneath the handrail in a barrier that provides containment, but no structural support to the main frame of the barrier.


Sheet material that occupies the space between supporting members.

Inner Pane

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

Inside Glazed

External glazing, where the glass is installed from within the building.

Insulating Glass

Fire-resisting glass fulfilling the criterion of E (integrity) and I (insulation).

Insulating Glass Unit (IGU)

An assembly comprising at least two panes of glass, separated by one or more spaces, hermetically sealed along the periphery.


The ability of glazing to remain complete and to continue to provide an effective barrier to flames for example.


The term applied to the material used in laminated glass to bond the glass leaves together. It can be either PVB, cast-in-place resin or intumescent.

Internal Glazing

Glazing in which neither side is exposed to the outside of the building.


The property of materials that swell and char when exposed to radiated heat, such as that from a fire, and forms an insulating barrier.


K Value

Former name for U-value on the Continent.


Insulated chamber for heating and cooling glass or ceramics.

Kerafix Tape

An intumescent tape used for glazing fire rated glass.


Lacquered Glass

Produced by depositing and baking lacquer coating on one side of clear glass. Two or more sheets of annealed or heat treated glass are separated by one or more plastic interlayers (normally PVB) and subjected to heat and pressure, in order to ensure perfect adhesion between constituent elements (see SGG STADIP, SGG STADIP PROTECT).


The annealing chamber on a float glass manufacturing line where the molten glass is subject to controlled cooling to obtain annealed glass, free from internal stresses, which can then be cut or worked.

Lehr End Size (LES)

Production width sized glass sheets i.e. 3210x2550/2250/2200 etc. Light Reflectance (RE (external) and RI (internal)) The proportion of the visible spectrum that is reflected by the glass.

Light Shelf

A "daylighting" device designed to redirect light towards the ceiling or back of the room.

Light Transmittance (T)

The proportion of the visible spectrum that is transmitted through the glass (formerly abbreviated to LT (Light Transmittance)).

Line load

See “Horizontal line load”.


Generic term for the various loads, where relevant, exerted on a structure or elements of a structure including wind loads, snow loads, imposed loads for example those associated with accidental human impact, and dead loads such as self-weight.

Location Blocks

Small blocks of resilient material placed between the edges of the glass and frame to maintain edge clearance and to prevent relative movement between the glass pane and surround. Blocks used on the bottom edge of the glass are known as “setting blocks”.

Long-Wave Shading Coefficient (LWSC)

See “Shading coefficient”.

Low Iron

Referring to extra clear glass, which has reduced iron oxide content in order to lessen the green tinge inherent to ordinary clear float glass.

Low Level Glazing

See "Safety critical glazing".

Low Modulus, Neutral Cure Silicone

A low modulus material requires a low force to stretch it and will generally have a good elasticity and therefore good movement accommodation. A low modulus, neutral cure silicone should be recommended for use in ‘wet’ glazed systems.

Low Emissivity or Low-E Glass

Glass with a special thin-film metallic or oxide coating which 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.Allows light to enter while also providing thermal insulation.

LT - Light Transmission Coefficient

The light transmittance and reflection coefficients are the ratio between the light beam transient or reflected by the glass and the stream of light falling on the glass.

LSG Ratio

Light to Solar Gain (LSG) is the ratio of the Visible Light Transmittance (VLT) and Solar Heat Gain Coefficient (SHGC) of a glass. In absolute percentage terms, a ratio greater than 1 signifies that the daylight passing through the glass is more than the sun’s direct heat passing through it.

Light Comfort

Lighting should contribute to the well-being of people in the room, ensuring optimal conditions for the eyes in terms of the amount and distribution of light (in such a way as to avoid both the risk of glare and underexposed angles).Light comfort is associated with the right choice of light transmission, as well as the location, direction and dimensions of the glass.


Magnetically Enhanced Cathodic Sputtering

See "Sputtered coating".

Main Seal

See "Secondary seal".


This refers to any technique for making areas of transparent glazing more apparent and easily noticeable, to help prevent people from walking into it.


A vertical framing section between glass panes.

Monolithic Glass

A single sheet of flat glass that could be annealed/toughened/heat strengthened.


Polished glass with a reflective coating of silver deposited on the back.


Nominal Thickness

Numeric designation to indicate the approximate thickness of glass.

Nickel Sulphide Inclusion (NiS)

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.

Non-Vision Area

See "Spandrel panels".


Notches and cut-outs are processes whereby areas of glass are removed from a sheet of glass, such an operation might be used where hinges or handles are required on frameless glass doors (there are limitations that apply and advice should be sought).


Noise is a sound stimulus, caused by vibrations or waves, spreading in the air, flowing or solid (eg in the wall). These are the minimum changes in air pressure that are recorded by the eardrum of our ear. The "audible" changes in air pressure are in the range of 0.00002 Pa to 20 Pa, while the atmospheric pressure is about 100,000 Pa.

Noise Intensity

The noise intensity ("strength") can be either large or small. The ear registers pressure changes between 0.00002 Pa and 20 Pa. Because this is a very wide range, we use the logarithmic scale.According to this scale, the noise level is expressed in decibels (dB). At the beginning of the scale 0 dB is the threshold of hearing, below which the human ear does not register anything, while 140 dB is the threshold of pain.


Octave band

The spectrum of sound is measured in bands of frequencies, an octave band is the band of frequencies in which the upper limit of the band is twice the frequency of the lower limit.

Off-Line Coating

See "Sputtered coating".

On-Line Coating

See "Pyrolytic coating".


Glass which has been fully enamelled or painted on one side to make it non-transparent.

Outer Pane

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

Outside Glazed

External glazing, where the glass is installed from the outside of the building.

Outdoor Light Reflectance (%)

Outdoor light reflectance, or daylight reflectance, is the percentage of light striking the glazing that is reflected back. It indicates the degree to which the glazing appears like a mirror from the outside.



A ready-to-be glazed single piece of glass or plastic glazing sheet material in a finished size.

Pack of Glass

Multiple sheets of glass of a specified size and type that are stacked against each other for transportation. They are not wrapped or packed in anything.

Patent Glazing (PG)

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

Patterned Glass

Translucent patterned glass, manufactured by rolling heat-softened glass between embossed cylinders (see SGG DECORGLAS, SGGMASTERGLASS).


Ability of a material to breakdown organic compounds on a surface using UV radiation (see SGG BIOCLEAN).


"Plateau Largeur Fabrication", SAINT-GOBAIN GLASS reference for jumbo-size flat glass sheets i.e. 6000mm x 3210mm dimensions.

Point Load

An imposed concentrated load acting on a square contact area of 50mm sides. Most often associated with balustrading and guarding applications and also to glass used in floors.

Perception of Light

Our perception of light applies only to electromagnetic radiation with a wavelength between 0.38 and 0.78 μm. Only this type of radiation causes a physiological phenomenon called vision, whose effectiveness depends on the wavelength. The luminous efficacy of different types of radiation allows for the conversion of the energy stream sent by the radiation source into the beam of light.


A roughly ‘triangular’ fillet of compound formed on the platform of the rebate in front of the glass.

Polished Edge

The ground edges are further refined by over polishing. This is especially useful for visible glass edges such as mirrors, table tops or glass showers.

Pre-Shimmed Tape

A preformed tape incorporating a continuous EPDM shimcord.

Preformed Tape

A butyl strip on fast release backing material.

Primary seal

A butyl-based sealant, for example polyisobutylene, applied to the edges of the spacer bar during assembly into IGUs, to ensure a watertight and airtight seal around the perimeter of the unit.


A coating applied to a surface to improve the adhesion of compounds or sealants.

PVB (Polyvinyl Butyral)

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


See "Pyrolytic coating".

Pyrolytic Coating/Coated

A specialist metallic coating is applied to the glass "on-line" during the float glass manufacturing process. The high temperatures involved result in the metallic oxides fusing into the surface of the glass through pyrolysis and effectively forming part of the glass (see SGG ANTELIO).

Partially Tempered Glass (TVG)

Partly Tempered Glass (TVG) is subjected to a heat treatment similar to the toughened safety glass (ESG). The glass is heated in the oven to more than 600 ° C, but not as fast as ESG (toughened safety glass) cooled. As a result, lower tensile and compressive stresses form in the glass. The flexural strength is between that of float glass and tempered glass. In the event of a break, cracks occur that run from the rupture center to the side edges. When processed into VSG, the larger-sized fragments result in a higher residual load capacity.


Residual Load Capacity (= Residue Stability)

Residual load-bearing capacity is a property of laminated safety glass (VSG) in which at least two glass panes are bonded together (laminated) by means of a PVB film. With glass breakage, the construction can still absorb certain loads due to the residual load-bearing capacity of the foil and prevents glass fragments from falling down.


The abbreviation for the sound reduction index when the spectrum adaptation term C is applied to the single number weighted sound reduction index (RW) using pink noise as a sound source.


The abbreviation for the sound reduction index when the spectrum adaptation term Ctr is applied to the single number weighted sound reduction index (RW) using traffic noise as a sound source.


Depends on the context in which it is being used. Normally refers to electromagnetic radiation. It is also used in terms of fire protection, see "fire resistance" and it is one of the ways in which heat can be transferred.

Radius Corner

Either an internal or external rounded cut edge on or within a pane of glass.


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

Reflective Coating/Coated

A metallic coating is applied to one side of the glass in order to significantly increase the amount of reflection by the glass of both the visible and infra-red (light and heat) range of the electromagnetic spectrum.

Road Traffic Noise

See “RA,tr”.


Certain thicknesses of annealed glass is considered suitable for use in large areas, in safety critical locations, for certain non-domestic situations such as shopfronts, showrooms, offices and public buildings. This is referred to in Building Regulations Approved Document N as robustness.

Roller Pick-up/Pluck

A phenomenon that occurs on toughened glass.

Rolled Glass

Translucent glass with 50-80% light transmission. Used where transparency of the glass sheet is not important or desired.


An optical phenomenon, generally noticed in reflection, caused by contact between glass and rollers in the horizontal toughening process.


See “Free path”.


See “Weighted noise reduction”.

Rw = rated sound reduction index

R W is the weighted sound reduction index of a component without sound transmission via a flanking component in dB.


Screen Printing

The printable side of the glass is placed under a canvas with motifs consisting of fabric stretched on a metal frame. The screen printing ink is now applied from below with a squeegee. In the places where the glass is not to be printed, the stitches of the textile fabric are dense, where the color is to be applied to the glass, the mesh are permeable. Application: For single and multicolored decors, in the area of facade and interior fittings.

Safety Critical Locations

Identified by Approved Document N and BS 6262 part 4 and defined as glazed sections of a door, wall or other part of a building most likely to be subject to accidental human impact.

Safety Glass

Glass which does not disintegrate into sharp and potentially dangerous splinters when broken. May be produced by laminating or tempering.


A fenestration surface that has a slope less than 60 degrees from the horizontal plane.


Enamelling the surface of a sheet of glass, either partially or completely, by means of a silk-screen and thermal toughening (see SGG SERALIT EVOLUTION).

Sheet Glass

A transparent flat glass with apparent glossy, fine finish but with waviness of surface.

Solar Control Glass

With the strong sunlight is also associated with a high energy input. That is, the short-wave radiation penetrates the glass and strikes surfaces that emit long-wave rays. These in turn cannot get through the glass to the outside, so that the heat accumulates in the room. It can come through the glass surfaces in the interior so the greenhouse effect. One way to prevent this is the installation of solar control glass. The solar control glass obtains its properties by coating and / or coloring the glasses, depending on whether colored or color-neutral solar control glass is to be produced. Dyes (for example iron oxide, copper oxide) are added to the colored so-called absorption glass in the glass melt. The glass with reflection in the non-visible area (infrared range).

Self-Cleaning Glass

Property of glass with a photocatalytic and hydrophilic coating. The coating harnesses the dual-action of UV light and rain (or water) to break down organic dirt and reduce the adherence of mineral material. The glass stays cleaner for longer and is easier to clean (see SGG BIOCLEAN).

Setting Blocks

See “Location blocks”


By roughening the glass surface by means of a sandblast blower, a complete satin finish or matting of the glass pane can be achieved. Furthermore, a pattern can be applied to the glass surface by the targeted processing by means of a fine sandblast.

Shading Coefficient (SC)

The g-Value (SF or TT) of a glass relative to that of 3mm clear float glass (0.87) and is used as a performance comparison. The lower the shading coefficient number, the lower the amount of solar heat transmitted. The short wave shading coefficient is the direct transmittance (T) of the glass as a factor of the solar factor or total transmittance (g) of 3mm clear float glass (T ÷ 0.87). The long wave shading coefficient is the internally re-radiated energy that the glass has absorbed as a factor of the g-Value (SF or TT) of 3mm clear float glass. It is determined by subtracting the direct transmittance (T) from the (g) of the subject glass and then dividing by the (g) of 3mm clear float glass (g-T ÷ 0.87).

Sight line

The perimeter of the opening that admits daylight.

Sight Size

The actual size of the opening that admits daylight.

Silicone Seal

Where the edges of double-glazed units are unframed and exposed to direct sunlight, they are sealed with silicone for UV resistance.


Bottom member of a frame, usually horizontal.

Silvering or Silvered

A process used in the manufacture of mirrors, whereby a silver coating is applied to one surface of the glass (see SGGMIRALITE EVOLUTION).

Sloped Glazing

See “Inclined glazing”.

Snow Load

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

Solar Factor g

The percentage of total solar radiant heat energy transmitted through glazing (the sum of energy transmitted directly and energy absorbed and re-emitted to the interior).

Solar Heat Gain

Solar radiant heat, transmitted or re-emitted by glazing into a building, contributing to the build-up of heat.

Sound Reduction Index (R)

A laboratory measure of the sound insulating properties of a material or building element in a stated frequency band.

Spacer Bar

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


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

Spandrel or Spandrel Panel

Glass cladding panels used in non-vision areas of a facade, commonly in curtain walling. They generally comprise an enameled or opacified glass to conceal building structure elements such as the edge of floor slabs.

Spectrophotometric Performance/Properties

The collective term for the transmittance, absorptance and reflectance properties of glass of solar radiant heat and light energy.

Sputtered Coating/Coated

An advanced metallic coating is applied to the glass "off-line" or after the float glass manufacturing process, by a technique called magnetically enhanced cathodic sputtering under vacuum conditions.


The ability of the specimen as a whole (not just the glass) to remain in position in its opening providing an effective barrier to fire (now normally referred to as “integrity”).

Stepped-Edge Unit

The edges of the double-glazed unit are not flush. One pane is larger and overlaps the other, to enable their use in roof glazing for example.

Stock Size

Manufactured glass products are available in standard sheet sizes:jumbos (PLF), lehr end sizes (LES) and standard stock sizes (SSS).

Structural Glazing

Glass acting as a structural support to other parts of the building structure, for example glass fins. It can also refer to glass that is fixed by means of bolted connectors where the glass is not acting as a structural element.

Structural Sealant Glazing

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

Supporting Member

An element of a glazing system/frame that supports and retains the edge of an infilling (glass).


Frosted glass has a matt surface on one side, which, for example, at Satinovo is achieved by treating the glass with acid (hydrofluoric acid). Frosted glass works well when privacy is desired, but light is allowed to pass through. Satinization can also be achieved using sandblasting.


Tempered Glass

See “Thermally toughened glass”.

Textured Glass

See “Patterned glass”.

Thermal Break

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

Thermal Fracture/Safety

See “Thermal stress”.

Thermal Stress

The term is used to describe the internal stresses created when a glass pane is subjected to variations in temperature within the body of the glass. If the temperature differentials in the glass are excessive, the glass may crack. This is referred to as thermal breakage or fracture. 

The most common example of the risk of glass cracking under the influence of thermal stresses concerns glass edges embedded in the groove, which when exposed to sunlight, warm up more slowly than its remaining surface.

Thermally Insulating Glazing

Double or triple glazed units provide thermal insulation.

Thermally Toughened Glass

Glass that has been subjected to a controlled heating and cooling process, in order to significantly increase its resistance to mechanical and thermal stress. Through the thermal toughening process, the glass attains its safe-breakage characteristics (see SGG SECURIT, SGG SECURIT HST, SGG SECURIPOINT).

Tempered Safety Glass (ESG)

Toughened safety glass (ESG) is produced from basic glass (float glass) by means of heat treatment. The glass is heated in an oven to more than 600 ° C and the air blowing abruptly cooled again. The near-surface zones of the disc cool faster than the inner core. This creates a tensile stress in the core in the surface. As an effect, this results in a much higher impact and impact resistance than with float glass. Furthermore, the glass disintegrates when destroyed in small crumbs without sharp edges whereby a risk of injury is significantly reduced. ESG has been used in the automotive industry for side windows for years (SAINT-GOBAIN Sekurit) and is also ideal for shower glass, glass for interior and sliding doors and many other applications.

Tight Size

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

Tinted Glass

A float glass to which colourants are added during manufacturing, resulting in tinting and solar radiation absorption properties.

Tin Side

Designation for the float glass side, which comes into contact with the tin bath. This is characterized by reduced mechanical strength, but increased chemical resistance. Recognizable by slight fluorescence under UV light.

Tinted Interlayer

A coloured pvb interlayer between two or more panes of glass.

Total Transmittance

See “Solar factor”.

Toughened Glass

See “Thermally toughened glass”.


Transmitting light but obscuring clear vision.


A horizontal framing bar between glass panes. It can also be used to refer to a fanlight over a door.


Clear, permitting vision.

Two Edge Glazing System

Infilling (glass) is supported continuously on only two opposite sides of its four edges by a suitable framing/glazing system.

T L Value

The T L value is the measure of the light transmission through the glass in the form of brightness. The indication of the light transmittance T L refers to the wavelength range of visible light from 380 nm to 780 nm and is weighted with the light sensitivity of the human eye (DIN EN 410).


Unframed Glazing

Glazing with one or more edges unframed.


This is a measure of the rate of heat loss of a building component. It is expressed as Watts per square metre, per degree Kelvin, W/m2K. Central unit of measure for the heat loss through a component: indicates how much heat per unit time passes through 1 m² of a component, if a temperature difference of 1 K (1 ° C) between the two adjacent sides (eg room and outside air) consists. The smaller the U-value, the better the thermal insulation. The unit of measure is W / m²K.


This is a measure of the rate of heat loss through the frame element of a window or door or other frame element. It is expressed as Watts per square metre, per degree Kelvin, W/m2K. It takes no account of the glass or spacerbar/edge seal (if an IGU is installed).


This is a measure of the rate of heat loss through a single pane of glass or an IGU for a heat energy flow through a 1 m² component at 1K (or ° C) temperature difference. It is expressed as Watts per square metre, per degree Kelvin, W/m2K. It is also known as a “centre pane” and takes no account of the spacerbar/edge seal (if it is an IGU) or any framing material it is installed into.

Uniformly Distributed Load (UDL)

Pressure exerted uniformly across a pane of glass, for example a wind load.

UV Transmittance

The percentage of solar energy in the form of ultra-violet radiation transmitted by glazing.


This is a measure of the rate of heat loss through the “whole window”. It is expressed as Watts per square metre, per degree Kelvin, W/m2K. It takes account of all elements forming the window, glass, spacerbar/edge seal (if it is an IGU) and the framing material itself.

Uw, eq Value

The Uw, eq value balances the heat flows at the window. The measure of the actual heat flow at the window is the Uw, eq value. By considering the solar energy gains dependent on the direction of the sky, together with the existing heat losses, the energy gain and loss are accounted for. The weighting with the window area shares per cardinal direction determines the Uw, eq weighted value for the evaluation of the total influence of the windows.


Vertical Glazing

Glazing which is either true vertical, or within 15° either side of true vertical.

Vertical Fenestration

Any type of fenestration other than skylights.

Visible Spectrum

Part of the electromagnetic spectrum, with wavelengths from approximately 380nm to 780nm, to which the human eye is sensitive. The combined wavelengths of the visible spectrum result in “white light”.

Vision Area

Areas of a facade which allow vision from the interior to the exterior.

Visible Light Transmittance (%)

Visible transmittance, or daylight transmittance, is the percentage of visible light striking the glazing that will pass through. Visible transmittance values account for the eyes’ relative sensitivity to different wavelengths of light. Glazing with a high visible transmittance appears relatively clear and provides sufficient daylight and unaltered views; however, it tends to create glare. Glazing with low visible transmittance is best used in highly glare-sensitive conditions, but can create gloomy interiors under certain weather conditions and diminished views. It is unsuitable for many day-lighting applications since it does not provide enough light for typical visual tasks. While glazing can have a high visible transmittance, it does tend to obscure views, e.g., frosted or patterned glass.


Warm Edge

Insulating glazings are kept in the edge bond with the help of a spacer profile "at a distance". The result is the noble gas or air-filled space between the panes, on which the insulating effect of the glazing is based. Due to the spacers, a linear thermal bridge of considerable length is created on the component window. Metal profiles heat to the outside more or less unchecked, along the entire transition area from glass to frame. For insulating glass spacers, which reduce the thermal bridge at the edge of the glass, thus keeping the room-side glass edge warmer. 'Warm edge' is a short name for thermally improved edge bond of insulating glass.


Strip material designed to control the passage of water and/or air through a joint in a glazing system or where a glazing system abuts other elements.

Weighted Noise Reduction

A single figure rating for the sound insulation of building elements. Includes a weighting for the human ear and measures actual sound transmittance.

WER (Window Energy Rating)

Window Energy ratings are a way for the consumer to reliably compare one product with another and make informed decisions regarding the energy performance of a window based on data provided on a “rainbow” label. The label gives a rating, A (best) to G (worst), based on the performance of the “whole window” (frame and glass) and therefore allows fair comparison of one window type with another.

Wind Load

The pressure, positive or negative, acting on an external surface of a building caused by the direct action of the wind. Commonly expressed as N/m2.

Wired Glass

Flat rolled glass reinforced with wire mesh and used especially for glass doors and roofing to prevent objects from smashing through the glass and also to hold pieces of broken glass together. Produced by continuously feeding wire mesh from a roller into the molten glass ribbon just before it undergoes cooling. Protects against break-in and fire spreading.

Warm Spacer Frame

At the edges of the insulated glass, special profiles - "spacer frames" are located between the individual glass panes. In this way, a space is created between the panes filled with noble gas or air, which forms the basis of the thermal insulation function of the window. Due to the use of spacers, a linear thermal bridge with a significant length is created. That is why it is extremely important to use appropriate, warm frames that ensure optimal thermal insulation.