Toughened or Tempered glass is produced by heating annealed glass to approxiametely 650ºC (1202ºF), at which point it begins to soften. The surfaces of this heated glass are then cooled (quenched) rapidly.

The technique creates a state of high compression in the outer surfaces of the glass. As a result, although most other characteristics remain unchanged, the bending strength is usually increased by a factor of four or five times that of annealed glass. When broken, the toughened glass fractures into small pieces. As these particles do not have the sharp edges and dagger points of annealed or Heat Strengthened glass, toughened glass is regarded as a safety glazing material.

Toughened glass must be cut to size and have any other processing, such as edgworking, cut-outs, notches or hole drilling, completed before being subjected to toughening, because attempts to "work" the glass after tougheneing will cause it to shatter.

The toughening process imposes limits on the maximum glass sizes. Wired glass, some patterned / figure rolled glass