PFG Glossary of Terms

Acid embossing

A process whereby the surface of flat or bent glass is obscured by treatment with hydrofluoric acids or its compounds.

Angle of incidence

The angle between the solar rays and a line perpendicular to the surface of the glass.


To prevent or remove stresses in glassware by controlled cooling.


A general term for old glass.

Arised edge

A small bevel not exceeding 2mm in width at an angle of about 45 degrees to the surface of the glass. It may be ground, smoothed or polished.


The sound reduction process in which sound energy is absorbed or diminished in intensity, as a result of energy conversion from sound to motion or heat.


The process of edge finishing flat glass to a beveled angle.


A gas-filled cavity in glass, larger than a seed.


A relatively large gas-filled cavity.

Bond breaker

A release surface to which the sealant will not adhere.

Brilliant cutting

A decorative process by which designs are produced on flat glass by means of abrasive and polishing wheels.


A synthetic rubber formed by co-polymerisation of isobutylene with a small amount of isoprene.


To fill a void with a sealant. Any oleoresionous sealant.


The process by which heat flows through or along a material, or from one material to another in contact with it.


The movement of air, gas or liquid, caused by difference in density due to temperature variations.

Curing agent

One part of a two-part compound that, when added to a base, will cause the compound to set by chemical action.


The optical effect due to variation of thickness of the sheet of glass.

Double glazing

Glazing which incorporates, instead of a single pane of glass, two panes separated by substantially stationary air, for the purpose of sound or thermal insulation or both. Installation is executed by the glazier into frames manufactured and positioned on site by others.

Double glazed units

Some form of framing which incorporates two panes of glass separated by stationary air, for sound and/or thermal insulation.

Edge cover

The amount of glass edge covered by the glazing bead. Also called ‘bite’.

Edge polish

A term applied to flat glass, the edges of which have been polished after cutting.

Edge work

Grinding, smoothing or polishing the edge of flat or shaped glass.

Float glass

A transparent glass, the two surfaces of which are flat, parallel and are fire-finished so that they give clear, undistorted vision and reflection. Manufactured by floating hot glass in ribbon form upon a heated liquid of greater density than that of the glass.


A pre-formed section, providing a continuous surround for the glass and a weathertight seal when compressed.


The securing of glass in prepared openings such as windows, door panels, screens and partitions.

Inside glazing

External glazing in which the glass is inserted from inside the building.

Outside glazing

External glazing in which the glass is inserted from outside the building.

External glazing

Glazing, either side of which is exposed outside the building.

Glazing compound

A setting or non-setting material used in glazing, applied by hand, knife or gun to provide a bedding for glass and a weathertight joint between glass and surround.

Multiple glazing

A form of glazed unit based on the same principle as double glazing, but using three or more panes of glass.


An extremely strong, resilient synthetic rubber formed by polymerization of chloroprene.


A piece of glass cut to size and shaped, ready for glazing (often called a square or a light).


A metal pin used in glazing to hold the glass in a metal frame.

Pot life

The time during which a two-part sealant remains usable after being mixed with a catalyst.

Safety glass

A glass so treated or combined with other materials, as to reduce the likelihood of injury to persons when it is cracked or broken.


A flexible material placed between two or more parts of a structure, with adhesion to the joining surface to prevent the passage of elements such as air, moisture, water, dust and others. Often used as cappings on joints filled mainly with other materials.

Sealed insulated glass units

Two panes of glass separated by a permanently sealed cavity containing some form of dehydrated gas. The units are prefabricated to the required size by the glass manufacturer.


Small, gaseous inclusions in glass.

Shelf life

The length of time that packaged materials can be stored under specific temperatures and still remain suitable for use.


A semi-inorganic compound derived from quartzite.


Glazing size (glass size) – The actual size of a piece of glass.
Sight size (daylight size) – The actual size of the opening which admits the light.
Tight size (full size, rebate size) – The actual size of the rebate opening.


The thickness of float glass.


Any frame, sash, casement or other building component into which glass is glazed.

Toughened glass (heat treated, tempered glass)

Glass, the surface of which has been rapidly cooled from near the softening point, so that a residual internal compressive stress remains after complete cooling. This increases the thermal and mechanical shock strength of the glass and tends to make it shatter in smaller and less dangerous fragments than ordinary glass if it is broken.


Permitting light to pass through with wide clear vision.


Permitting light to pass through but with different degrees of obscuration and diffusion.

X-ray protective glass

A glass which contains a high percentage of lead oxide and sometimes barium oxide, which has a high degree of opacity by x-rays.

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