How Does Safety Glass Work?
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About Safety Glass
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Safety glass is either of two types of glass--tempered glass and laminated glass--that are manufactured in ways that make them more difficult to break and safer if they do happen to shatter. The need for stronger and safer glass arises in many areas, such as law enforcement, cooking and construction, but both types of glass are best known for making up the windows and windshields of automobiles. The importance of safety glass in automobiles is readily apparent, as a windshield or window made of normal glass could be easily shattered by a stone kicked up by another vehicle, which would create a burst of jagged glass shards toward the driver or passengers.
Tempered Glass
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Tempered glass is the type of glass used in the normal windows of a car. The glass is made through a process called tempering, which involves super-heating then quickly cooling glass several times, which causes the molecular structure of the glass to change, making it many times harder. The tempering process also makes the tempered glass brittle, so that if an impact force has enough power to crack the hardened surface, the glass will tend to shatter all at once, throughout the entire piece of glass. Another important feature of tempered glass is that instead of shattering into jagged shards, it breaks up into small cubes or stone-like pieces, which are not very sharp and don't have adequate weight to cut the skin when falling or flying through the air. Tempered glass also provides a degree of heat resistance, making it useful in devices such as ovens, computer screens and coffee makers.
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Laminated Glass
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Laminated glass is the type of glass that makes up car windshields. Laminated glass is made by sandwiching two pieces of glass around a central layer made of polyvinyl butyral (PVB), a strong flexible material that bonds to the glass. When a piece of laminated glass breaks, the layer in between the panes prevents shards of glass from flying around, since the glass remains stuck to the plastic layer in the middle. Since the plastic layer is somewhat flexible and will not shatter, even if the glass is broken, it can be difficult to break all the way through. This makes laminated glass preferable to tempered glass for security applications, like in jewelry stores, prisons and other places where preventing glass penetration is important. Laminated glass is also useful for its sound reduction and ultraviolet light-blocking properties. Laminated glass can also be increased in strength by using multiple layers of PVB and glass.
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