The toughening process increases the usability of the glass by increasing the strength of the glass surface, which makes the form much more resistant to mechanical factors. Glass hardening consists in heating the glass to 620 – 680 C and cooling it in a stream of compressed air, which results in surface expansion and compressive stresses, which significantly increases the strength of the glass. Tempered glass is a safety glass, because when broken, it breaks down into crumbs, not needles, eliminating the risk of injury.
Glass toughens for 3 key reasons:
- mechanical strength is increased – up to 3 times more resistant to impact than ordinary glass,
- increased thermal resistance – up to 4 times higher than ordinary glass (for basic 4 mm float glass the range of toughening is from – 50 C to + 20 ° C, where for ordinary glass of the same thickness it is respectively -20 to + 50 ° C),
- each toughened glass has machined edges (blunted or ground) so that they can be safely grasped in the hands, eliminating the risk of injury.