Welcome to the Glass Glossary, a collection of terms designed to demystify the language of glass technology and design. Whether you’re a seasoned professional or just starting your journey in the world of glass, this glossary provides a comprehensive guide to key terms, ensuring clarity and understanding.
Acid Etching
Acid etching is a technique used to create patterns or designs.
Acoustic Insulation
The ratio of external sounds passing through a glazing surface.
Argon
An inert, nontoxic gas is used to fill insulating units, thus improving thermal performance.
Arrised Edge
An edge-finishing technique that involves removing the sharp edges from cut glass panes.
Bevel
Bevels are glass that is UV bonded onto glass panes to create a decorative design.
Bevelling
The process by which an edge of glass is finished to a bevel angle.
Broken Down/Blown Double Glazed Unit
This is a glass double-glazed unit that has misted up inside due to moisture ingress.
Cut Outs
The glass has internal or external shapes cut out such as for switches, sockets or cat flaps.
Double Glazed Units
Two panes of glass enclosing a sealed airspace.
Drilled Glass
Holes drilled through the glass or mirror usually for fixing.
Double-Glazed Unit: Two panes of glass separated by a cavity and hermetically sealed in a factory, to provide thermal and/or acoustic insulation.
Edge-polished
A glass finishing process of polishing edges.
Fire-resistant Glass
A special type of glass designed to contain flames and inflammable gas for a longer period.
Fogging
A reaction caused by glass condensation.
g-value (g): Abbreviation or symbol for Solar factor according to EN 410, formerly abbreviated to SF or TT.
Gasket: Pre-formed glazing materials used for bedding or securing glass and to separate the glass from the frame or fixings.
Glazing: The securing of glass into prepared openings. 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.
Guarding: The prevention of people falling wherever there is a change in floor level by means of a permanent barrier.
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 to BS 6206.
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.
HST: Abbreviation for heat soak test. This is an additional form of heat-treatment, 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”.
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.
Impact performance / resistance: When related to safety glazing this is the classification of safety glass when tested to BS 6206.
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.
Inner pane: The pane of a double-glazed unit which faces the interior of a building.
Insulating glass: Fire – resisting glass fulfilling the criterion of E (integrity) and I (insulation).
Insulating unit: See Double-glazed Unit.
Integrity: The ability of glazing to remain complete and to continue to provide an effective barrier to flames for example.
Interlayer: 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.
Intumescent: The property of materials that swell and char when exposed to fire.
K value: Former name for U-value on the Continent.
Laminated Glass
Laminated glass consists of two or more layers of glass with one or more interlayers made of plastic or resin. If the glass breaks, the interlayer keeps the fragments bonded together.
Leaded Glass
Glass pieces joined with lead strips and joints soldered to hold the pieces together.
Low-E Glass
Low-E (low-emissivity) glass is a type of energy-efficient glass designed to minimise the amount of ultraviolet and infrared light that passes through without compromising the amount of visible light. It has a microscopically thin coating that reflects heat, keeping indoor temperatures consistent. In winter, it reflects interior heat back into the room, while in summer, it reflects exterior heat away, thus enhancing thermal performance and reducing energy costs.
Low Iron Glass
Low iron glass is ultra clear and provides a higher degree of transparency than clear float glass.
Mirror
Mirror glass, also known as mirrored/silvered glass, is a type of glass that has a reflective coating on one side, typically made of metallic materials like silver or aluminum. This coating creates a reflective surface, allowing the glass to function as a mirror.
Nickel sulphide inclusion: A rare, but naturally occurring impurity present in all glass that can, in certain circumstances, lead to spontaneous breakage of thermally toughened glass in service.
Non-insulating glass: Fire resisting glass, providing the criteria of E (integrity) only.
Non-vision area: See Spandrel panels.
Obscure Glass
Any type of glass with uneven surfaces that offers light diffusion and privacy.
Pane
A sheet of glass.
Painted Glass
Paint sprayed onto one side of sheet glass most often used for splashbacks in kitchens and bathrooms.
Polished Glass
The edges or the glass have been arrised and polished to give a smooth surface.
RA: 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.
RA,tr: The abbreviation for the sound reduction index when the spectrum adaptation term Ctris applied to the single number weighted sound reduction index (RW) using traffic noise as a sound source.
Radiation: 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.
Rebate: 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.
Resin laminate: Two or more sheets of glass assembled with one or more resin inter layers. The resin is available in a wide range of colours for decorative purposes. Often used to laminate heavily textured glasses and thick glass assemblies for example to use in floors.
Road traffic noise: See “RA,tr”.
Robustness: Certain thicknesses of annealed glass is considered suitable for use in large areas, in safety critical locations, for certain non-domestic situations such as shop fronts, showrooms, offices and public buildings. This is referred to in Building Regulations Approved Document N as robustness.
Rollerwave: An optical phenomenon, generally noticed in reflection, caused by contact between glass and rollers in the horizontal toughening process.
Run-up: See “Free path”.
Rw: See “Weighted noise reduction”.
Safety Glass
Glass which must have passed an impact test and either must not break or must break safely.
Screen printed Glass
Screen-printed glass is tempered or heat-strengthened glass, one face of which is covered, either partially or totally, with mineral pigments.
Self-cleaning Glass
A special extremely thin coating of microcrystalline titanium oxide which reacts to daylight. This reaction breaks down filth on the glass, with no need for detergent. When it rains, a hydrophilic effect is created, so water and dirt slide off.
Stained Glass
Coloured flat glass or any object made of such glass joined by lead came or copper foil.
Toughened Glass/Tempered Glass
Toughened glass is two or more times stronger than annealed glass. When broken, it shatters into many small fragments which prevent major injuries.
Triple Glazing
Three panes of glass enclosing two hermetically-sealed air spaces.
U-value
This is a measure of the rate of heat loss of a building component. It is expressed as watts per square metre, per degre Kelvin, W/m2K.
Vertical glazing: Glazing which is either true vertical, or within 15° either side of true vertical.
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 resulting “white light”.
Vision area: Areas of a façade 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, they 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.
