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Thermal tempering is a process used to strengthen glass and increase its resistance to thermal stress and mechanical forces. This is done by heating the glass to a high temperature, then cooling it rapidly. This process introduces compressive stress on the surface of the glass, while the core remains in tension, making the tempered glass piece stronger and more durable.

In the first stage of thermal tempering, the glass piece is heated to a high temperature, typically around 620 Celsius (1150 Fahrenheit). This is done in a special oven, called a tempering furnace, which evenly heats the entire glass surface. During this heating process, the glass becomes soft and pliable, making it easier to shape and mold if desired.

Once the glass has reached the desired temperature, it is quickly cooled down, a process called quenching. This involves transferring the glass from the tempering furnace to an area with high-pressure air jets. The high-pressure air rapidly cools the outer surfaces of the glass, causing them to contract, while the core remains relatively hot and in a softened state. This temperature difference creates the compressive stress on the surface, while tension is introduced to the core.

The rapid cooling in the quenching process causes the glass's surface to become compressed, and the core is in tension. This creates a balanced, strong structure that significantly improves the properties of the glass. Tempered glass is typically four to five times stronger than annealed (untreated) glass, making it more resistant to breakage, bending, and thermal stress. When tempered glass does break, it shatters into small, relatively harmless pieces rather than large, sharp shards, reducing the risk of injuries.

Due to its increased strength and safety features, tempered glass is widely used in various applications, such as: 1. Automotive industry: Windshields, side windows, and rear windows 2. Building and construction: Glass doors, windows, balustrades, and partitions 3. Household appliances: Oven doors, glass cooktops, and refrigerator shelves 4. Electronics: Protective screens for smartphones, tablets, and other devices 5. Furniture: Glass table tops and shelves In conclusion, as a glass piece is thermally tempered, it is heated to a high temperature to become soft and pliable. The rapid cooling process introduces compressive stress on the glass surface, making the glass stronger and more resistant to breakage, bending, and thermal stress. Tempered glass also shatters into small, harmless pieces, reducing the risk of injuries. This enhanced strength and safety make tempered glass suitable for various applications, such as in automotive, construction, appliances, electronics, and furniture.