Much of the glass that’s used for residential and commercial applications is tempered safety glass. In short, tempered glass is heat-treated, making it about 4x stronger than regular, annealed glass. By design, when broken, tempered glass disintegrates into small pieces and is much less likely to do harm.  

When shattered, tempered glass windows can help protect a building’s occupants and equipment from the hazards of large shards of fragmented glass debris. 

Below, we discuss what makes tempered glass different from standard glass and its key benefits and potential downfalls.

What is Tempered Glass?

Manufactured through a process of extreme heating and rapid cooling, tempered glass is much harder than standard glass. Regular, annealed glass undergoes a thermal tempering process that increases its strength and changes its composition to shatters differently. 

The glass is heated in a furnace to over 1,000 degrees Fahrenheit and then quickly cooled using high-pressure air blasts. This cools the outer layers of the glass much more quickly than the internal layers, so when the inside cools, it pulls away from the outer layers. As a result, the inside remains in a state of tension, while the outside goes into a state of compression. These competing forces are what make tempered glass so much stronger than annealed glass.

Due to the tempering process, when this type of glass is broken, it breaks into small, rounded chunks instead of sharp, jagged shards.  Regular, untreated glass is known to shatter into sharp pieces called spall, which are a significant cause of injury in the cases of extreme weather or attacks like bomb blasts. Tempered glass is often referred to as “safety glass” for its ability to prevent spall and keep building occupants safe. 

What is Tempered Glass Used for?

Also known as “safety glass”, tempered glass is often used in car windows, shower doors, glass tables, and other installations where increased safety standards are necessary. While the manufacturing process does make tempered glass more resistant to force, it is not shatterproof glass or unbreakable in any way. For this reason, it shouldn’t be used to prevent intruders, but it will stand up to more force than regular glass. 

The tempering process also makes tempered glass more resistant to damage from higher temperatures. That’s why you may see tempered glass used in situations where high temperatures are likely to cause glass to break like in fireplace doors or kitchen appliances.