Speaker 1: Welcome to Brainstuff from how stuff works dot com where
Speaker 1: smart Happens. Hi, I'm Marshall Brain with today's question, how
Speaker 1: does safety glass work? Automakers began using laminated safety glass,
Speaker 1: also known as auto glass, for automobile windshields in nine.
Speaker 1: To make laminated safety glass, the manufacturer sandwiches a thin
Speaker 1: layer of a flexible, clear plastic film called polyvinyl Beauty
Speaker 1: Roll or PVB between two or more pieces of glass.
Speaker 1: The plastic film holds the glass in place when the
Speaker 1: glass breaks, helping to lessen injuries from flying glass. The
Speaker 1: film can also stretch, yet the glass still sticks to it.
Speaker 1: It's also quite difficult to penetrate laminated safety glass compared
Speaker 1: to normal window glass. For example, if a rock rolls
Speaker 1: off the back of a truck, it's probably not going
Speaker 1: to come through the windshield. The laminated safety glass will
Speaker 1: stop it. And Laminated safety glass also helps to hold
Speaker 1: occupants inside a vehicle during a wreck, although it often
Speaker 1: causes facial cuts in the process. Banks use a multiple
Speaker 1: layer laminated glass to help stop bullets. Laminated safety glass
Speaker 1: has two additional benefits. First, it reduces the transmission of
Speaker 1: high frequency sound, and second, it blocks of ultra violet radiation.
Speaker 1: Laminated safety glass is also used in things like cutting boards,
Speaker 1: greenhouse windows, shower enclosures, and office partitions, any place where
Speaker 1: breaking glass could cause injury. It also resists falling out
Speaker 1: of its frame during an earthquake or a tornado. Tempered
Speaker 1: safety glass is a little bit different. It's a single
Speaker 1: piece of glass that gets tempered using a process that
Speaker 1: heats and then quickly cools the glass to harden it.
Speaker 1: The tempering process increases the strength of the glass five
Speaker 1: to ten times over that of untempered glass. Tempered safety
Speaker 1: glass breaks differently than regular cleared glass. When tempered glass
Speaker 1: is struck, it doesn't break into sharp, jagged pieces of
Speaker 1: shrapnel light glass, as normal window panes and mirrors do. Instead,
Speaker 1: it breaks into tiny pebble light pieces without sharp edges.
Speaker 1: It's used in the side and rear windows of automobiles.
Speaker 1: Besides car windows, tempered safety glass is also used in
Speaker 1: computer monitors, liquid crystal displays, skylights, refrigerator shelves, oven doors,
Speaker 1: and storm doors. You can easily spot tempered safety glass
Speaker 1: in an automobile rear window on a sunny day if
Speaker 1: you're wearing polarized sunglasses. Tilt your head ninety degrees or so,
Speaker 1: and you will see a symmetrical diamond pattern in the
Speaker 1: glass created during its tempering process. For more on this
Speaker 1: and thousands of other topics, visit how stuff works dot com.