Auto safety glass, simply put, is either the rear windshield or the front windshield. Both are treated and manufactured in different ways, but both will also prevent extensive injuries to you and your passengers in the event of an accident. Here is how these two types of glass are made, why they are placed in their respected positions, and what it means when one or both of them break in your vehicle.
Tempered glass is thermally and/or chemically treated to increase the outer pressure and inner tension of the piece of glass. It makes the glass much stronger and more resilient. Only intense force can break tempered glass, and even then the glass shatters into cubed little chunks rather than jagged shards. This type of glass is only used in the rear windshield. A different type of glass is used in the front windshield.
Laminated glass takes a few thinner sheets of glass and "glues" them together using a laminating process and thin sheets of an acrylic polymer. As a result of the laminating process, when this glass breaks, it cracks and releases as a sheet instead of shards. Doing so protects your face, neck, eyes, chest, and arms from thousands of potentially lethal and/or blinding cuts. That is why laminated glass is always used as the front windshield, and not vice versa with the rear windshield glass.
When the Glass Breaks
If you get a crack in the front windshield, you could actually let the problem go for weeks, even months, since it will not suddenly break and cause injuries to you and your front seat passenger. However, it is still a good idea to get the glass replaced as soon as you are able because extremely cold temperatures can cause the breaks or cracks to worsen. If the cracks are especially bad, the windshield can leak a lot of rainwater into the vehicle and all over the dash.
If the rear windshield cracks, it will continue to crack and shatter all over, leaving glass all over the back seat and making it not so safe for people riding in the back of the vehicle. Despite its safety features, these bits of rear windshield safety glass can still cut and hurt people. If the rear windshield breaks, you will need an immediate auto safety glass replacement as the rear glass will just cave inward and leave your car's interior exposed to the elements. Contact a service, like Harr's Auto Glass, for more help.