Heat-strengthened is made by heating float glass, cooling down, and adding heat treatment process to produce a compression stress layer on surface.

Compared with float glass of same thickness it is approximately twice stronger under wind pressure and also in thermal crack stress. Since it hasn't been cooled down rapidly like tempered glass does, its strength under wind pressure is weaker in comparison with tempered glass, however unlike tempered glass, it will not suddenly cracked without any stress from outside. And if it fractures, the way is close to that of float glass.