Glass is tempered by taking annealed glass and heating it to softening point of approximately 660 degree C. Its structure is then rapidly cooled while the inner core is allowed to cool gradually. This results in layer of high compression on the surface counter balancing by high tension at the center resulting in a glass that is four to five times stronger than annealed glass. Should accidental breakage occur, the resulting fragments are smaller and granular, causing no injury, harmless.
Toughened glass is 4 to 5 times stronger than annealed glass, has enhanced thermal resistance, and breaks into small cuboid fragments rather than irregular shards of glass.
Toughened glass is made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace that heats it to above its annealing point of 600 °C.
It is then rapidly cooled with forced draughts of air while the inner portion of the glass remains free to flow for a short time.
Impact Resistance - A surface compression of over 10,000 PSI(69MPa) imparts about five times the impact and mechanical strength of annealed glass of the same thickness.
Thermal Cracking Resistance - Tempered Safety Glass will resist temperatures of up to approximately 295 C an temperature difference of up to approximately 250 C. In a range frm -20 C to 300 C.
Safety - When broken, Tempered Glass / Toughened Glass become small granules, which will not exert substantial hurt to human body.
Optical Clarity - Tempered safety glass may contain some minor visual imperfection of distortion through the heating