Glass Selection Guide
Annealed, heat-strengthened or tempered? Compare strength, safety, break pattern and cost before you order.
Annealed vs Heat-Strengthened vs Tempered
| Criteria | Annealed Glass | Heat-Strengthened | Tempered (Toughened) |
|---|---|---|---|
| Relative strength | 1× — baseline | Approx. 2× annealed | 4–5× annealed |
| Break pattern | Large, sharp shards | Larger pieces, partly contained | Small blunt fragments (safe) |
| Safety classification | Not safety glazing | Not safety glazing in most codes | Certified safety glazing |
| Thermal shock resistance | Up to approx. 40 °C | Up to approx. 100 °C | Up to approx. 200 °C |
| Processing after heat treatment | Allowed — any cutting, drilling, edging | Not possible — must be finished first | Not possible — must be finished first |
| Flatness / optical distortion | Excellent | Very good | Slight roller wave, within EN 12150 limits |
| Typical applications | Furniture, picture frames, secondary glazing, further processing | Spandrel panels, laminated make-ups, high-load facades | Doors, shower enclosures, facades, balustrades, table tops |
| Relative cost | Lowest | Medium | Higher (heat treatment included) |
Selection tips
Use safety glass wherever impact is possible
Doors, shower enclosures, balustrades and low-level glazing should always be tempered or laminated to meet local building codes.
Finalise sizes before heat treatment
Tempered and heat-strengthened glass cannot be cut or drilled afterwards. Confirm dimensions, holes and notches before production starts.
Combine processes for higher performance
Laminating tempered or heat-strengthened glass adds post-breakage retention, which is required for overhead glazing, skylights and structural balustrades.
Match the glass to thermal load
For large dark-coloured facade panels, heat-strengthened laminated glass limits spontaneous breakage risk while keeping better flatness than tempered glass.
Frequently Asked Questions
Can tempered glass be cut after tempering?
No. Every cutting, drilling, edging and notching operation must be completed before the glass enters the tempering furnace. Any attempt to work the glass afterwards will cause immediate breakage.
What is the difference between heat-strengthened and tempered glass?
Heat-strengthened glass is cooled more slowly, reaching roughly twice the strength of annealed glass and keeping larger fragments when broken. Tempered glass is cooled rapidly to reach four to five times annealed strength and crumbles into small blunt pieces, which makes it a certified safety glass.
Can you supply test certificates with the order?
Yes. Each production batch can be shipped with EN 12150 or ANSI Z97.1 test reports, EN 14179 heat soak certificates and a full packing list showing thickness, size and quantity.
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