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What is tempered glass and how do tempering ovens work?

Posted by Ontario Glazing Supplies ,2019 Aug 8th
What is tempered glass and how do tempering ovens work?

Tempered glass is likely a term you have heard but do you know what it is? It is a material that has many applications and likely appears in many aspects of your daily life. Here we will discuss exactly what tempered glass is, how it is made and some of the benefits and common uses.

What is Tempered Glass

Tempered glass is defined as, glass that is primarily made for safety purposes by using a controlled thermal or chemical treatment to make it much stronger than annealed or standard glass. These methods of “tempering” the glass put the center into tension and the outer glass into compression. This is what gives tempered glass it’s strength and also allows it to crumble into small pieces when broken as opposed to creating dangerous shards like conventional glass. This makes it much less likely to cause serious injury when broken. There are a few ways to tell if glass has been tempered. These include examining the edges and looking for a manufacturer’s mark that says “tempered” or “temp”.

How is Tempered Glass made?

The process of creating tempered glass is a multi-step process. The first part of the process involves cutting the glass to the desired size because any cutting or fabrication after heating the glass can cause the glass to break or lose strength. Next, the glass is put into a tempering oven and rapidly heated to a high temperature. After it is removed from the oven, it is “quenched” or cooled rapidly with air. This creates an effect where the outer glass cools much more quickly than the center. This is what gives the glass it’s tension and strength. At the end of the process, the tempered glass is at least 4 times stronger than annealed breaking at a psi of 24,000 to 6,000 for annealed glass.

How do Tempering Ovens work?

Tempering ovens need to allow the glass to heat up to about 630 degrees Centigrade, or about 1,165 Fahrenheit. When inserted, the glass rolls over ceramic rollers to ensure even heating. Uneven heating in a tempering oven can cause many issues such as bowing, edge-wrinkling and shape changes. Any of these conditions can affect the strength of the glass. Tempering ovens also use convection to move the air and create even heating. This can either be done by blowers or naturally through openings on either side of the oven. Using a tempering oven is a very manual process that involves a lot of experience as a lot can go wrong due to a number of factors such as thickness of the glass, heating time and more.

Common Tempered Glass uses

There are many uses for tempered glass. Anywhere that requires stronger and safer glass could use or may already be using this material. Some of the most common places you see tempered glass in everyday life include automobile windows, computer, TV, and mobile phone screens, home appliances, windows in tall buildings, glass shower enclosures, and many more places.


As you can see, tempered glass has many uses and is more prevalent in your daily life than you ever realized. The process of creating it is relatively simple but requires a tempering oven and a lot of skill to make it just right.