Toughened glass or tempered glass is treated to be far more resistant to breakage than simple annealed glass and is up to five times as strong as ordinary glass which means that it has to be hit much harder in order to break. Also when it does break it is into lots of small pieces which are much less dangerous instead of splintering into large shards as plate glass, thus providing a major safety advantage in all of its applications.
Toughened glass is made from annealed glass treated with a thermal tempering process. A sheet of annealed glass is heated to above its “annealing point” of 600°C. Its surfaces are then rapidly cooled while the inner portion of the glass remains hotter. The different cooling rates between the surface and the inside of the glass produces different physical properties, resulting in compressive stresses in the surface balanced by tensile stresses in the body of the glass.
These counteracting stresses give toughened glass its increased strength. Toughened glass is physically and thermally stronger than regular glass. Any cutting or grinding must be done prior to tempering. Cutting, grinding, and sharp impacts after tempering will cause the glass to fracture.
Toughened glass has extremely broad applications in products because of its safety and strength. As a result it is used in a number of demanding applications, including windows, glass shower doors, architectural glass, sliding glass doors, glass tables, glass balconies, glass office partitions, kitchen glass splashbacks, glass balustrades, walk on glass and many other applications.