Tempered glass has been used for centuries, but the original users probably didn't even know what they had. The accidental use and development of tempered glass has lead to an extremely durable and much safer product.Depending on the intended use, glass can be composed of a variety of ingredients including silica, sodium carbonate, lime, magnesium oxide and aluminum oxide. Glass is created by heating the required materials to the melting point, forming the liquid glass into a usable form, then cooling it. Since the process to temper glass is simply to reheat the finished product and then cooling it, the likelihood of someone accidentally tempering glass is quite high. Because the process to temper glass is so simple, historically, people may have used tempered glass more often than they realized.A well known example of centuries-old tempering is Prince Rupert's Drop, also called Dutch Tears, which were created as early as 1625 by plunging a drop of molten glass into cold water. The resulting teardrop or tadpole-shaped form had unique properties. The outside of the teardrop cooled quickly, including the tail of the teardrop, producing a compressive stress on the outside of the bulb. The inside of the teardrop's bulb cooled more slowly, contracting inside the colder outer shell. The core of the drop was in a state of tensile stress - it could be hit with a hammer and still not break. The tail of the teardrop which cooled quickly was brittle and easily broken. If the tail was broken, the entire teardrop would shatter into miniscule pieces, virtually disintegrating.Francois Royer de la Bastie invented what we now know as tempered glass in 1874. Bastie discovered that by heating and reheating glass, it was more difficult to break. And when it did break, it broke into small granules rather than large shards of glass. Rudolph A. Seiden, born in 1900, saw the beginnings of what would become the Holocaust in his native Austria and moved to Kansas City, Missouri in 1935. Seiden was the first person to obtain a patent for the process used to temper glass.The first cars didn't have any glass installed, but they didn't need to. The speed of the earliest cars was so slow it was akin to a stroll in the park. As cars became more powerful and more sophisticated, they also became more dangerous. Wind, flying pebbles and other debris would hit the drivers. The first windshields were constructed of plain glass, but it didn't take long to realize this was a bad idea. Both tempered glass and laminated glass became popular at the beginning of the 1900s. Henry Ford was the first car manufacturer to insist on using laminated glass windshields. Tempered glass was used for the sides and rear windows.Laminated glass is stronger than tempered glass, but also more expensive. The automobile industry found that laminated windshields worked well and provided better protection to the driver and passengers. Tempered glass is used for the rest of the car because it is less expensive and provides easier access to trapped riders in an accident. A metal object can quickly turn the side and rear windows into a pile of tiny pieces of glass that look like small pebbles.