How Auto Safety Glass Works
America’s first motorists were truly pioneers. Lacking a windshield and sporting an “open air” design, the first automobiles exposed motorists to wind, rain, airborne gravel, and the occasional low-flying bird. Motorists out for a simple Sunday drive had to don protective headgear, goggles and gloves. They also had the unenviable task of scraping bugs from their garments when they got home.
As the automotive industry began to evolve, so did the comfort and safety features of automobiles. And in the mid 1920s, windscreens or windshields made their debut as standard equipment.
The first windshields employed a single sheet of plate glass to protect motorists from the elements. Chosen primarily for economic reasons, plate glass was thought to be strong enough for the job. But when plate glass shatters it breaks into large pieces of sharp glass that can pose a serious hazard.
Then in the late 1920s, it was Henry Ford to the rescue. After being injured himself by a shattered plate-glass windshield, Ford developed the laminated safety glass windshield. Laminated safety glass is made by sandwiching a layer of polyvinyl butyrate (PVB) plastic between two pieces of glass. What makes this idea perfectly suited for windshields is that the plastic inner layer prevents large shards of glass from showering vehicle occupants. An additional benefit is that the plastic also gives the glass an energy-absorbing, cushioning quality that can help keep passengers inside the vehicle in the event of an accident. This technology has not changed much since Ford invented it 75 years ago.
Watch Your Temper
While laminated safety glass is used for windshields, tempered glass is typically found in the side and rear windows of automobiles. Tempering strengthens glass through the application of heat and pressure. The end result is glass that crumbles into small “pebbles” when broken. These pebbles reduce the possibility of flying-glass injury because they aren’t sharp.
Tempered safety glass is also used in computer monitors, liquid crystal displays, skylights, refrigerator shelves, oven doors and storm doors.