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What is Tempered Glass?

Sonia Nair Apr 23, 2019
Otherwise known as toughened glass, tempered glass is a type of safety glass that is much stronger than regular glass.
Glass is something that has to be handled with care, because it can break into shards that can cause severe injuries and lacerations. So regular glass is not usually used in applications that can pose such danger. In such cases, toughened glass or tempered glass is preferred.
This glass is used in numerous applications, like sliding glass doors, windows of passenger vehicles, diving mask, cookware, refrigerator trays, oven doors, etc. It is said to be four to five times stronger than the regular glass, and does not break into sharp-edged shards that can cause injuries.


This glass is made extra strong through the process of manufacturing that involves extreme heating, followed by rapid cooling with forced air drafts. Even though tempered glass refers to the fully tempered glass, this term is used interchangeably with heat-strengthened glass too.
While the heat-strengthened version is only twice as stronger as the regular glass, fully tempered glass is almost four to five times stronger. This glass is much valued for its strength.
One of the advantages of tempered glass is that it breaks into small, oval-shaped, pebble-like pieces, and thus eliminates the risk of injury. It is found to be more resistant to high temperatures, as compared to regular glass, and are less prone to develop cracks.
Unlike the regular glass that breaks into pieces, the entire tempered glass panel shatters at once. The disadvantage of this glass is that it is cut to the required size, and pressed into the desired shape, before toughening. Once tempered, it cannot be re-worked easily.

How to Cut Tempered Glass

In order to cut tempered glass, you have to heat it to around 900 degrees, and then allow it to cool for eight to ten hours.
  • Place the glass in a craft oven, which is set to 900° F. Heat it till it reaches this temperature, and then turn off the oven.
  • Allow the glass as well as the oven to get cool for at least eight to ten hours. Once it gets cool, remove the glass from the oven, and keep it on a flat surface.
  • Keep the T-square along the cut line. Use a glass cutter, which is dipped in kerosene (this helps in achieving a smoother cut).
  • Gently cut the glass with the cutter, along the straight edge. Make sure to apply a moderate pressure and finish the task with one smooth motion, along the entire line. This action should not be repeated for a second time.
  • All you have to do is to insert an ¼ inch dowel just beneath the scratch you have made on the glass, and gently apply pressure on either side of the scratch, so that the glass breaks through the scratch.
  • Use a whetstone to rub along the cut edges of the glass, so as to give a round finish to its edges.
You should never try to cut tempered glass directly. Before cutting tempered glass, you have to heat and cool the glass as mentioned here. Above all, always wear eye protection and gloves while cutting glass, so as to avoid accidental injuries.