Glass is strong enough for windows, jars and bottles in normal use, but it can be broken very easily. When safety is important, glass which has been specially strengthened is used. Cars used to be fitted with a toughened (heat-treated) glass windscreen. When toughened glass breaks it shatters into small pieces instead of leaving sharp splinters.
Windscreens are now made from laminated glass — a glass ‘sandwich’ with a layer of plastic in the middle. Laminated windscreens may crack but they don’t shatter, greatly reducing the risk of injury. Other sorts of strong glass include wired glass and bulletproof glass, which is made from several sheets of glass separated by plastic layers.
Laminated and wired glasses are both made by rolling. The plastic or wire is sandwiched between two sheets of glass. The strong glass is then annealed and cut to size. Laminated glass is perfectly clear and is ideal for car windscreens or shop windows, to prevent people from getting hurt if the glass breaks. Wired glass is used where falling glass would be dangerous. If the glass melts in a fire, the pieces are held in place by the wire. Invented in 1895, wired glass was the first safety glass ever made.
Today’s windscreens are made from laminated glass. On impact, the windscreen may crack, but because of its triple layer construction, it will not shatter. This reduces the chances of people being cut or injured by flying glass.
Fighter planes are fitted with a bulletproof windscreen – often up to 12 cm thick.
Picture Credit : Google