Glass glossary
The words on our drawings, quotations and specification sheets, in plain English.
A
- Annealed glass
- Ordinary glass, cooled slowly after it is made. It can be cut and drilled, and breaks into sharp pieces.
- Arris
- A small bevel ground along a cut edge to take off the sharpness. Included on every cut-to-size piece.
B
- Back-painted glass
- Glass painted on the back face, as used for splashbacks.
- Balustrade
- A barrier at the edge of a stair, landing, balcony or other drop, to stop people falling.
- Base channel
- A continuous metal channel fixed to the floor or slab edge that holds frameless balustrade glass along its bottom edge.
- Bevel
- A sloping polished border ground around the face of a mirror or glass.
- Black edge
- Dark marks at the edge of a mirror where moisture or the wrong cleaner or adhesive has lifted the silver.
- Build-up
- The layers that make up a glass: for laminated glass, the panes and interlayers, such as 10 + 1.5 + 10 mm.
C
- Critical location
- A place where people are likely to strike the glass: doors, glass beside doors and low glass in walls. Approved Document K asks for safety glass there.
- Cut-out
- A shape cut out of the glass, such as for a socket or a hinge.
F
- Float glass
- Flat glass made by floating molten glass on molten tin. The base for most other glass.
- Frameless
- Glass held only at its base or by small fittings, with no frame around its edges.
G
- Guarding
- Approved Document K's word for a barrier that protects people from falling.
H
- Heat soaking
- A test in which toughened glass is held at about 290 °C so that panes with nickel sulphide inclusions break in the oven (BS EN 14179-1).
- Heat-strengthened glass
- Glass heat-treated to about twice the strength of annealed glass. Not a safety glass on its own.
I
- Interlayer
- The plastic layer that bonds the panes of laminated glass together and holds the pieces if it breaks.
J
- Juliet balcony
- A barrier across a full-height opening with no platform to step onto.
L
- Laminated glass
- Two or more panes bonded with an interlayer, so the glass stays in place if it breaks.
- Line load
- A horizontal load along the top of a barrier, in kilonewtons per metre (kN/m), set by BS EN 1991-1-1 for the type of use.
- Low-emissivity (low-E) glass
- Glass with a coating that reflects heat back into the room, used in double glazing.
- Low-iron glass
- Extra-clear glass without the green tint of ordinary glass.
M
- Manifestation
- Marking on large areas of glass so people see it, placed at two heights by Approved Document K.
N
- Nickel sulphide inclusion
- A rare tiny particle in glass that can expand and cause a toughened pane to break on its own. Heat soaking reduces the risk.
- Notch
- A cut-out at the edge or corner of a piece of glass.
P
- Point load
- A load on a small area of a barrier's infill, in kilonewtons (kN).
- Polished edge
- An edge ground flat and polished to a clear finish.
R
- Raked
- A panel with a sloping top edge, to follow a sloping ceiling.
S
- Safety glass
- Glass that breaks safely under impact: toughened or laminated glass classed under BS EN 12600.
- Sealed unit
- Two or more panes sealed around a gap, as in double glazing (BS EN 1279).
- Spigot
- A stainless steel post fixed to the floor that clamps the bottom of a frameless glass panel.
T
- Toughened glass
- Glass heated and cooled quickly to make it four to five times stronger than ordinary glass; it breaks into small blunt pieces (BS EN 12150-1).
U
- U-value
- How much heat passes through a window or roof light, in watts per square metre per degree (W/m²K). Lower is better.
- Uniformly distributed load (UDL)
- A load spread evenly over an area, in kilonewtons per square metre (kN/m²).