Glasses can be heat-treated to increase their resistance to mechanical and thermal stresses
There are three types of heat treatment:
-heat-strengthened glass -thermally toughened glass -thermally toughened and Heat-Soak treated glass
When broken, thermally toughened glass and thermally toughened and Heat-Soak treated glass fragment in such a way that they can be considered safety glasses. This is not the case with heat-strengthened glass