Welcome to Brainstuff from how stuff works dot com where smart Happens. Hi, I'm Marshall Brain with today's question, how does safety glass work? Automakers began using laminated safety glass, also known as auto glass, for automobile windshields in nine. To make laminated safety glass, the manufacturer sandwiches a thin layer of a flexible, clear plastic film called polyvinyl Beauty Roll or PVB between two or more pieces of glass. The plastic film holds the glass in place when the
glass breaks, helping to lessen injuries from flying glass. The film can also stretch, yet the glass still sticks to it. It's also quite difficult to penetrate laminated safety glass compared to normal window glass. For example, if a rock rolls off the back of a truck, it's probably not going to come through the windshield. The laminated safety glass will stop it. And Laminated safety glass also helps to hold occupants inside a vehicle during a wreck, although it often
causes facial cuts in the process. Banks use a multiple layer laminated glass to help stop bullets. Laminated safety glass has two additional benefits. First, it reduces the transmission of high frequency sound, and second, it blocks of ultra violet radiation. Laminated safety glass is also used in things like cutting boards, greenhouse windows, shower enclosures, and office partitions, any place where breaking glass could cause injury. It also resists falling out
of its frame during an earthquake or a tornado. Tempered safety glass is a little bit different. It's a single piece of glass that gets tempered using a process that heats and then quickly cools the glass to harden it. The tempering process increases the strength of the glass five to ten times over that of untempered glass. Tempered safety glass breaks differently than regular cleared glass. When tempered glass is struck, it doesn't break into sharp, jagged pieces of
shrapnel light glass, as normal window panes and mirrors do. Instead, it breaks into tiny pebble light pieces without sharp edges. It's used in the side and rear windows of automobiles. Besides car windows, tempered safety glass is also used in computer monitors, liquid crystal displays, skylights, refrigerator shelves, oven doors, and storm doors. You can easily spot tempered safety glass in an automobile rear window on a sunny day if
you're wearing polarized sunglasses. Tilt your head ninety degrees or so, and you will see a symmetrical diamond pattern in the glass created during its tempering process. For more on this and thousands of other topics, visit how stuff works dot com.