The side windows and rear windshield of a car are made of tempered glass, which is created by rapidly heating glass to more than 1000 degrees Fahrenheit and then rapidly cooling it to room temperature. This process, known as tempering, makes the glass many times stronger than untempered glass of the same thickness. Most vehicles use tempered glass for rear windows and doors, while the windshield is made of laminated glass. Laminated glass is composed of two pieces of glass with a thin layer of vinyl between them, and it is designed to offer the highest levels of safety in the event of an accident.
When tempered glass breaks, it breaks into small pieces that mimic the shape of pebbles. On the other hand, when a small object hits a piece of laminated safety glass, usually only the outer layer of the windshield that is hit breaks. In severe impact situations, the glass “breaks” but usually does not separate because broken glass pieces generally adhere to the vinyl inner liner. Automotive glass is also used for sunroofs; they are designed to be UV-resistant to help passengers enjoy natural light without harmful UV rays.
In addition, automotive glass is designed to be resistant to dust, dirt and impacts to prevent annoying particles from sticking to the glass and distorting the driver's line of sight. Although laminated glass is widely used in the automotive industry, it has a wide range of applications and can work well in any situation where there is a potential for impact by a person. Laminated glass can be repaired, but tempered glass breaks completely in an accident and requires a complete replacement. The most important type of automotive glass is the windshield, which is made of laminated glass.
This “fool-proof” design consists of two strong glass sheets that become a single thick sheet by sandwiching a layer of polyvinyl butyral in the middle. Although laminated glass is limited to car windshields, it can be used for any application where there is a potential for impact by a person.