Its easy to forget how important an automobiles glass is to the vehicle. After all, if its doing its job, youre looking right through it. But auto glass is manufactured for structure, safety and aerodynamic purposes. Automobile glass has changed throughout the years, and the current materials used reflect the current peak of automotive engineering.
Glass evolution
The first windshields were plates of glass, not unlike the type of glass found in home windows. By the late 1920s, however, Ford vehicles were using a less dangerous type of glass called laminated glass. Tempered glass debuted in 1938 and is still often used for rear window and side window (door) applications. Current auto glass manufacturers make several types of glass for modern vehicles, including hydrophobic glass and heat-strengthened laminated glass.
Fabrication
Auto glass is composed of four primary components: sand, dolomite, soda ash and limestone. About 70 percent of auto glass is sand. Windshields are made using a laminate process that adheres two sheets of glass to a layer of vinyl. Side and rear windows are made from tempered glass, which is glass that is heated to more than 1,000 degrees and then rapidly cooled.
Safety standards
All modern automobile glass must meet the specifications outlined by the American Glass Replacement Safety Standards Council and the American National Standards Institute. Tests include the front-impact test, which states that the windshield should not dislodge from the vehicle during a 30-mile-per-hour crash; and the roof crush test, which tests the durability of the windshield when 5,000 lbs. or 1 1/2 times the weight of the vehicle, whichever is less, is applied to the vehicles roof.
Tinting
Many states regulate the use of window film and tinting products. For windshields, most states prohibit darkening the windows below a factory specified mark on the front window called AS1. Some states are more specific, as Alabama allows for 6 inches of tinting, Hawaii allows for 4 inches and West Virginia permits 5 inches. Regulations also vary by state on the amount of visible light that must be allowed to pass through side and rear windows. Some states, such as Pennsylvania, mandate that 70 percent of available light pass through the tinting product. Other states, such as Kentucky, are more permissive, allowing 15 percent of available light. Check regulations with your state to verify what is allowed in your state.
