Tempered glass also referred to as toughened glass or safety glass is used for most glass fencing, glass railings, glass shower enclosures, storefronts and curtainwalls,frameless glass interior doors & kitchen back splash applications. It is also used to make stove tops, cookware, tableware & glass furniture.
Toughened glass is made by starting with a standard sheet of float glass with the required thickness. The float glass sheet is then prepared, sized & shaped to customers requirements by cutting, drilling of any holes & working the edges of the glass. The edges can be polished, grounded, arrised, bevelled etc. This preparation work can only be done before the tempering process as once the glass has been toughened, it can not be re-worked, meaning it can not be cut, drilled or re-shaped anymore.
The tempering process is when the prepared piece of float glass is laid flat on rollers & fed into a furnace which heats the glass to around 620 degrees Celsius. At this temperature the glass reaches its molten state or melting point. The molten glass is then fed into a quenching chamber where it is rapidly cooled (quenched) with high pressure cool air. This sudden cooling causes the surface of the glass to contract rapidly inducing compressive stresses whilst the centre of the glass remains in tension. As a result of these stresses the glass is toughened .This make the glass way stronger than the same piece of glass before the toughening process. Tempered (safety) glass is also far more resistant to impact stress & temperature changes than normal glass.