Tempered glass is commonly used in applications where it is necessary for the glass to be exteremely strong, durable, and yet safe at the same time. For example, in vehicles, tempered glass is used instead of regular glass for it provides a higher level of strength and safety for passengers. Why is it safer? When tempered glass breaks, it does not splinter into dangerous shards of glass. Rather, it shatters into thousands of tiny pieces of almost harmless pieces of glass.
Tempered glass is manufactured using a simple two-step process: the glass is heated to a very high temperature and is rapidly cooled down. Since cutting tempered glass is virtually impossible (it will shatter), production plants must cut and shape the glass into its final form before tempering it.
As mentioned above, before a sheet of glass can be tempered, it needs to be cut into its final form. The sharp edges are then removed with the help of sandpaper or other similar abrasive material. The glass is then carefully inspected to ensure it has no structural defects. After this stage, the glass must be thoroughly cleaned.
Once the glass is ready for tempering, it is placed into a special oven (or series ovens). These ovens range in design style – some can handle only one piece of glass at a time, while others are assembly-line types of ovens and can handle large quantities of glass at once. However, all of them are capable of reaching temperatures above 600° C which is required temperature in order for glass to become properly tempered.
Quenching is the next stage of the tempered glass production process. It basically means cooling down the surface of the glass. It is important to quickly cool down the outer surface, while letting the inner part of the glass cool down more slowly. This ensures rapid compression of the very outer edge of the glass, while the inner part of the glass remains in tension. Cold air jets are used to quickly cool the surface area of the glass.
It is interesting to note that water is not used for tempered glass quenching. Why? Because it would cool down the entire surface area of the glass at the same time. It is possible to use specific chemical substances instead of water or cold air, but because chemical cooling is not economical, the cold-air jets are used more often. Basically, there are two major components of the tempered glass manufacturing process: extreme heating of the glass followed by rapid cooling with cold air.
There are certain standards that must be met by every piece of tempered glass. Tempered glass must withstand direct pressure equalling 10,000 pounds (or more) per square inch. While that may sound like a log of pressure to withstand, most tempered glass windows found in automobiles can easily withstand up to 20,000 pounds of pressure per square inch.
The automobile industry uses more tempered glass than other industry in the world. Tempered glass is used in many other applications as well, such as home and commercial construction (shower doors or all-glass doors used by the public). You’ll also find it heavily used in practically every kitchen: stoves, coffee pots, refrigerator shelves, etc.