What Is Tempered Glass?

Tempered glass is a safety glass that is around four times stronger than annealed (non-tempered) glass. All tempered glass pieces must meet the ANSI standard Z-97.1-1966 and any other adoptions to that standard by the Department of Labor.

Annealed glass breaks into jagged, sharp pieces which can be large in size. Annealed glass is extremely dangerous when its broken & can be life threatening. Tempered glass breaks into very small, relatively harmless pieces. Due to these reasons it is, by law, a requirement in areas which can pose a threat to human life.

What makes glass tempered?

After a sheet of glass has been made and cut to size, it is cleaned and then heated to 1100 degrees (the softening point for glass). The glass is then flash cooled with cold air along the edges of the unit at a rapid rate, this process is called quenching. This creates a tension zone along the edge of the sheet.

As the center cools, at a slower rate, tension begins to pull towards edges. This is now the compression zone, giving the tempered piece is strength.

  • Annealed glass breaks into sharp and jagged pieces which can be large in size and is extremely dangerous and is life threatening. Tempered glass breaks into very small, relatively harmless pieces which is not nearly as dangerous and annealed glass.

  • The stamp above, and those similar to it, are required by law to be in a corner of any piece of tempered safety glass.