Why does glass in cars shatter into so many pieces

A.� Car makers use safety glass in all their vehicles. There are two different types and they tend to use laminated glass for windscreens and tempered glass for side and rear windows.

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Q. What's the difference
A. The laminated glass is really two pieces of glass with a thin layer of plastic film sandwiched in the middle. When the glass breaks, it sticks to the plastic, stopping it flying in all over the passengers and drivers. The layer of plastic will also stop small objects like stones penetrating the windscreen. That's why you can sometimes feel a tiny crack on the outside of your windscreen, but not on the inside.

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Q. Does it do anything else for the driver
A. Sure, it reduces sound levels in a car and it can block over 90% of ultraviolet radiation.

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Q. So what's the difference between laminated and tempered glass
A. Tempered glass gets its strength from being heated then cooled quickly to harden it. And it breaks in a different way.

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Q. How can it break differently
A. The process means that when the glass shatters it tends to split into tiny pieces with rounded edges rather than sharp fragments. This is why you see those little pieces of glass on the pavement if someone has broken the side window of a car to rob it.

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Q. Does tempered glass look different
A. Not if you look at it with the naked eye. But if you're wearing sunglasses, sometimes you can see a pattern in the glass that looks like tartan. That is caused in the tempering process.

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