WEBVTT - How does safety glass work?

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<v Speaker 1>Welcome to Brainstuff from how stuff works dot com where

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<v Speaker 1>smart Happens. Hi, I'm Marshall Brain with today's question, how

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<v Speaker 1>does safety glass work? Automakers began using laminated safety glass,

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<v Speaker 1>also known as auto glass, for automobile windshields in nine.

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<v Speaker 1>To make laminated safety glass, the manufacturer sandwiches a thin

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<v Speaker 1>layer of a flexible, clear plastic film called polyvinyl Beauty

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<v Speaker 1>Roll or PVB between two or more pieces of glass.

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<v Speaker 1>The plastic film holds the glass in place when the

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<v Speaker 1>glass breaks, helping to lessen injuries from flying glass. The

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<v Speaker 1>film can also stretch, yet the glass still sticks to it.

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<v Speaker 1>It's also quite difficult to penetrate laminated safety glass compared

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<v Speaker 1>to normal window glass. For example, if a rock rolls

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<v Speaker 1>off the back of a truck, it's probably not going

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<v Speaker 1>to come through the windshield. The laminated safety glass will

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<v Speaker 1>stop it. And Laminated safety glass also helps to hold

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<v Speaker 1>occupants inside a vehicle during a wreck, although it often

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<v Speaker 1>causes facial cuts in the process. Banks use a multiple

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<v Speaker 1>layer laminated glass to help stop bullets. Laminated safety glass

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<v Speaker 1>has two additional benefits. First, it reduces the transmission of

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<v Speaker 1>high frequency sound, and second, it blocks of ultra violet radiation.

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<v Speaker 1>Laminated safety glass is also used in things like cutting boards,

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<v Speaker 1>greenhouse windows, shower enclosures, and office partitions, any place where

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<v Speaker 1>breaking glass could cause injury. It also resists falling out

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<v Speaker 1>of its frame during an earthquake or a tornado. Tempered

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<v Speaker 1>safety glass is a little bit different. It's a single

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<v Speaker 1>piece of glass that gets tempered using a process that

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<v Speaker 1>heats and then quickly cools the glass to harden it.

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<v Speaker 1>The tempering process increases the strength of the glass five

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<v Speaker 1>to ten times over that of untempered glass. Tempered safety

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<v Speaker 1>glass breaks differently than regular cleared glass. When tempered glass

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<v Speaker 1>is struck, it doesn't break into sharp, jagged pieces of

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<v Speaker 1>shrapnel light glass, as normal window panes and mirrors do. Instead,

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<v Speaker 1>it breaks into tiny pebble light pieces without sharp edges.

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<v Speaker 1>It's used in the side and rear windows of automobiles.

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<v Speaker 1>Besides car windows, tempered safety glass is also used in

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<v Speaker 1>computer monitors, liquid crystal displays, skylights, refrigerator shelves, oven doors,

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<v Speaker 1>and storm doors. You can easily spot tempered safety glass

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<v Speaker 1>in an automobile rear window on a sunny day if

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<v Speaker 1>you're wearing polarized sunglasses. Tilt your head ninety degrees or so,

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<v Speaker 1>and you will see a symmetrical diamond pattern in the

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<v Speaker 1>glass created during its tempering process. For more on this

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<v Speaker 1>and thousands of other topics, visit how stuff works dot com.