Beginning life as ordinary annealed glass, what makes toughened or tempered glass different is the subsequent thermal treatment to increase its strength.
After being cut to the correct dimensions, the glass is heated to an extraordinarily high temperature - over 700°C - and then quickly cooled. The outer surfaces of the glass cool significantly faster than the centre, and it is this part of the process that gives the glass its tough qualities. Stresses build up between the core and the outer layers, giving the glass around five times its original strength.
If hit, the whole pane of toughened glass fragments into small, blunt pieces and falls out, which vastly reduces any risk of injury. However, due to its nature, all shaping, cutting and drilling work must be done before the toughening process is begun.
As a result of its safety features, this type of glass is ideal for use in a range of applications. You will find this type of glass in products such as car windows, glass doors, diving masks, some plates and cookware, and as an element of bullet-proof glass.