How is Tempered Glass Made?

Most of the glass that people encounter in public settings is a glass known as tempered glass, which is known to be stronger and safer than annealed (regular) glass. Tempered glass is approximately 5 times stronger than annealed glass and will not shatter into sharp pieces that can lead to serious injury. Instead, tempered glass breaks into little cubes should it experience an impact powerful enough to break it.

What makes tempered glass stronger and safer than annealed glass? The answer lies in the manufacturing process.

The manufacturing process of tempered glass is as follows:

1. Preparation

Cutting the glass to the correct specifications is first required before starting the tempering process to guarantee the integrity of the glass. The glass is then checked for any flaws, such as cracks, which lowers the possibility of the glass breaking during the tempering process. The glass is then cleaned to make sure there are no imperfections, such as sharp edges, on the glass which can alter the quality of the glass before starting the heat treatment process.

2. Heat Treatment

After the glass is cut to the desired specifications, checked for flaws, and cleaned; the glass is put through the heat treatment process. During the heat treatment process, the glass goes through a tempering oven as a feed or as a batch where the glass is heated to approximately 620°C. The high temperature that the glass is exposed to is vital in the process of strengthening the glass.

Once the glass has passed through the tempering oven it is ready to go to the next step of the manufacturing process, which is quenching.

3. Quenching

As the glass exits the tempering oven, it is put through a cooling process known as “quenching”. During this cooling process, high-pressure air is shot at the glass’ surface from a variety of nozzles at various angles for a duration of 3 to 10 seconds. The exterior surface of the glass cools significantly faster than the inside of the glass. As a result of the quenching process, the centre of the glass tries to peel away from the outside surface as it cools. This leads to the outside surface of the glass to compress while the centre remains tense, which gives tempered glass its strength.

After the tempering process, the glass has the following properties:

  • Versatility: Tempered glass can be moulded into a variety of shapes and designs. This allows tempered glass to be used in different settings, such as shower doors, windows, glass doors, car windows, kitchen appliances, smartphone screens, and balustrades to name a few.
  • Impact Resistance: Compared to annealed glass, tempered glass has far higher impact resistance. This makes tempered glass ideal for environments where there is a higher possibility that glass will be exposed to impacts.
  • Strength: Tempered glass is more suitable for applications in structures and settings where there is a significantly higher environmental load or possibilities of impacts. This is due to tempered glass being 5 times stronger than annealed glass.

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