Many companies have their own formulas for achieving different effects. The mechanical properties of glass can be altered by heat strengthening or tempering. By reheating and then quickly chilling the glass, it is made anywhere from two to six times stronger than untreated glass and able to stand up to greater temperature extremes. The drawback to tempered glass is that when it does break, the fragments are small and, consequently, dangerous. Glass can also be chemically treated for strength, which makes it suitable for paving or flooring.
Safety glass is made by sandwiching glass between layers of plastic.
The addition of these layers reduces sound transmission as well. But the biggest advances in glazing are the films, now virtually transparent, that are layered on the surface of the glass or integrated during manufacture. They have the ability to selectively reflect or absorb different types of solar energy. Used together with tints and laminates, these films significantly extend the range of applications for glass. Introduced in 1989, low-e was intended for cold climates, where it reduces energy loss by reflecting heat back into a living space.