Lamination is what makes modern day bullet resistant glass possible. Here is how the idea of laminating glass came to be. Laminated glass was discovered on accident by a French chemist in 1903. Edouard Benedictus came across the invention through carelessness in the laboratory when he dropped a glass beaker, which had been coated with a plastic cellulose nitrate, on the floor. The beaker broke into pieces but did not come apart. He realized that this was due to the viscous collodion that lined the inside of the beaker. This gave way to the development of a glass-plastic composite for use in automobiles. Although it was not immediately adopted by the automobile industry it found widespread use in the military as eyepieces for gas masks during World War I.
Ruprecht von Wittlesbach is supposed to have invented “Prince Rupert’s Drops,” which are considered by some to be an early precursor to bulletproof glass. “Prince Rupert’s Drops” are essentially quenched teardrop shaped bits of glass. They are formed when molten droplets of glass are allowed to fall into water, which rapidly cools the glass. This greatly increases the toughness of the glass except at the end of the droplet’s tail. If the droplet is struck on the end of its tail it will burst almost explosively into small fragmented pieces. By World War II glass laminates were commonly used as a form of bulletproofing. The bulletproof glass of World War II was much heavier that made today. The bulletproof laminate was made by gluing sheets of glass together with liquid rubber. This form of bulletproof glass was anywhere from 100 to 120 mm thick. Over the years the materials have improved allowing laminates to withstand larger impacts at reduced weights and dimensions. Today laminated glass is used for a number of things ranging from car windshields to hurricane protection to bullet resistant windows in government buildings.