Auto glass starts out just like all other glass products. It is made from an amorphous solid material that is typically very brittle and optically transparent. Many items are made from this material including windows in homes and offices, drinking vessels, and pretty items used to decorate the home. Almost all items that are created from this substance have the common factor of sand.
Soda lime glass is the most familiar substance used in making the drinking vessels and windows, and even auto glass. The big problem with the sods lime substance is that it is brittle, and when it breaks it breaks into large pieces that can injure people severely. To be used as auto glass the substance needs to be harder to break than the average drinking vessel is. The soda lime substance must be tempered before it can be used as windshields in automobiles, or as doors on commercial properties.
The tempered variety of this soda lime substance is much harder to break than the original version is. With the material in its original state you can easily break it with very little force. Once the material is tempered you can barely break it unless you manage to strike it on the very edge of the piece. The tempering process makes the material stronger and it also makes the material break into small pieces when it does break instead of into large sections. Small pieces cause less damages to humans when they come into contact with them.
In order to temper the material it is gotten hot to the point of melting, and then it is cooled very slowly. This variety of the familiar material is called annealed glass. During this process the strength of the material is made to be ten times what it was originally. The heating and cooling of this material takes place in a leer, which is a type of kiln.
This special kiln is needed to bring the substance to the annealing temperature or annealing point. At this temperature the substance is still too hard to release from its formed shape, but it is soft enough that all of the stresses it contains can relax. Once this point has been reached the item will be allowed to soak up heat until it is an even temperature throughout. Once the heat soaking process is complete the substance is cooled to a temperature that is less than the strain point. Once this temperature has been achieved it is safe for the item to be quickly dropped to room temperature. At this time the piece can be drilled, cut to size, or polished.
Auto glass is put through the annealing processes for the added strength, but mainly for the safety features annealed glass has. When a window in a car is broken it breaks into those tiny little pieces that are less likely to cause deadly injuries. The officials that oversee the production of cars and automobiles require that the safety variety be installed.