Glass
Toughened glass
Toughened glass is glass heated and then chilled with air jets to put its surface under compression, making it several times stronger than annealed glass of the same thickness. Made to BS EN 12150, it breaks into small, relatively blunt pieces rather than long sharp shards.
Where does it work well?
Shop doors, frameless entrances, low-level panes and other glazing in a critical location, where a strong safety glass is needed and the holes, notches and final size can be fixed before the glass is made.
Pros
- Several times stronger than annealed glass
- Breaks into small blunt pieces
- Suits frameless doors
- Handles heat stress well
Cons
- Cannot be cut or drilled after toughening
- Falls out of the frame when it breaks
- Edge damage can cause sudden failure
How long does it last?
Typically lasts as long as the frame if undamaged, though rare spontaneous breakage can occur.
What should you check when buying?
Ask for BS EN 12150 marking on each pane, and state the BS EN 12600 impact class needed for the position. All holes and cut-outs must be made before toughening. For overhead or high-risk panes, ask whether heat soaking to BS EN 14179 is worthwhile.
Common questions
Can toughened glass be cut to fit?
No, toughened glass cannot be cut or drilled after it has been processed, as it would shatter. Every size, hole and notch must be set first, which is why replacement panes are always made to measure.
What is heat soaking?
Heat soaking holds toughened glass at high temperature to break any panes carrying a nickel sulphide inclusion before they reach site. BS EN 14179 covers the process. It reduces the risk of spontaneous breakage but does not remove it entirely.