Toughened Glass
Toughened Glass is made from normal glass via a thermal tempering process in which the glass is subjected to heat till its Softening point and then rapidly cooled. This gives the glass its strength and safety characteristics from the compressive and tensile Stress built up inside the glass due to snap cooling. When an impact takes places, the missile has to penetrate the compressive layer of the glass to break it. When toughened glass breaks it disintegrates into small pieces which greatly reduces the chances of injuries and if there are any then they are superficial in nature.

Toughened Glass is 4-5 times stronger than annealed glass with higher resistance to thermal stress as edge quality is much better. Toughened Glass can withstand temperature upto 295° Celsius and temperature differentials upto 150° Celsius.

Breakage pattern of Toughening Glass
(Higher strength, breaks in blunt pieces)

Heat  Strengthened Glass:

When annealed glass is heated up to a temperature range of 600° Celsius to 650° Celsius, for a specified time and then suddenly air-cooled. It gives strength to the glass. The most important factor of heat-strengthened glass is that it has very less wave distortion as compared to fully toughened glass. The glass breaks into slightly bigger pieces and moves towards edges. It is approximately 2-3 times stronger than annealed glass.  The chances of breakage are very little during transportation  and handling. With the probability towards Nickel Sulphite (NiS) inclusions, spontaneous breakage becomes practically non-existent.

Breakage pattern of H.S.Glass
(When broken, tends to hold the splinters together)

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