Tempered glass is produced by heating glass to near melting point (approx. 650℃ and rapidly cooling the surface uniformly with air. Glass produced by this special process has enhanced strength and is used mainly for the rear and side windows of vehicles. It has the characteristic of fracturing instantly if broken.
Tempered glass is manufactured by generating compressive stress on the surface through quenching glass after heated to near melting point. When the glass is broken by tensile force, the force is counteracted by the surface compressive stress. Tempered glass is three to five times stronger than ordinary glass at the same thickness.
Tempered glass is strong. But if subjected to an external force that exceeds the limit of the compressive stress, it will fracture. Unlike ordinary glass, however, if broken, it fragments into small pieces. As there are no sharp, knife-like shards, it is unlikely to cause serious injury. That is why tempered glass is recognized as safety glass.