Most vehicle windshields are made of laminated glass, which is considered effective in preventing theft due to the effort required to break them. Tempered glass, on the other hand, is used for the opposite reason. The glass used for the front and rear door windows and the rear window is usually tempered, while the windshield is made of laminated glass. Laminated glass is designed to withstand extreme impacts without breaking, helping to prevent injuries from flying shards of glass or passengers being thrown through the windshield.
Safety glass is used in all automotive glass, and it is made to reduce the likelihood of injury if broken. Laminated glass is made up of two pieces of glass with a thin layer of vinyl between them, which are then laminated together by applying heat and pressure in an autoclave. When a small object hits a piece of safety glass, usually only the outer layer of the windshield that is hit breaks. Tempering produces a piece of toughened glass that is four to five times stronger than before the tempering process.
This type of glass is most commonly used in passenger windows of cars, while laminated glass forms the front and rear windshields most of the time. When tempered glass breaks, it is designed to break into small pieces that are less likely to cause additional injury or damage. Vehicles often have different types of glass because each type has a different purpose. Automotive glass is exceptionally durable and responsible for 60% of the car's structural integrity in rollover accidents, while absorbing 45% of the crash impact during a head-on collision.
If broken, tempered glass is designed to disintegrate into small pieces of glass the size of rock salt. Laminated glass is widely used in the automotive industry due to its strength and durability. It consists of two pieces of glass with a thin layer of vinyl between them that are bonded together at high temperatures. In addition, laminated glass can be repaired, but tempered glass breaks completely in an accident and requires a complete replacement. Automotive glass is also 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. The second type of aftermarket automotive glass comes from the OEM, but was created on a different production line. Tempered glass is manufactured by rapidly heating it to more than 1000 degrees Fahrenheit and then rapidly cooling it to room temperature.
This “tempering process” makes it many times stronger than untempered glass of the same thickness.