Toughened glass forms small granules when broken.
Toughened glass is made from annealed glass via a thermal tempering process. Producing toughened and heat strengthened glass begins with the feeding by conveyor of cut-to-size annealed sheets of glass (with minimum arrised edges) into a furnace.The glass oscillates back and forth on ceramic rollers to an approximate temperature of 620ºC.Under computer control, the glass moves into the quench where it is rapidly cooled by high pressure cool air. This 'snap' cooling or quenching induces compressive stresses to the glass surface, while the centre remains in tension. Although the physical characteristics remain unchanged, the additional stresses created within the glass increases its strength by 4–5 times (for toughened glass) compared to that of annealed glass of equal thickness.