The Bullet Proof Glass industry evolved from a series of accidental discoveries dating back to the 1640s.
The idea of tempered glass was first discovered by Prince Rupert of the Rhine, when he dropped hot molten glass into cold water. The glass rapidly cools but only on the surface, creating a shell for the hotter glass contained inside. As the inside cools, it contracts against the already hardened exterior creating a compressed chamber and making the glass substantially more durable. This lends itself to high impact resistance.
The idea of laminated glass evolved from another accident. This time, by the French chemist Edouard Benedictus in 1903. While working in his lab, Benedictus accidentally dropped a beaker that was coated in plastic cellulose nitrate. He noticed when the beaker hit the ground it cracked, but did not split apart in pieces.
Benedictus went on to register the first safety glass patent in 1909 after bonding a piece of plastic cellulose between two sheets of glass. Using Prince Rupert’s method of immediately chilling the glass, the safety glass becomes much stronger and if it does crack, it will not shatter.
Today, there are two types of bullet resistant glass: solid acrylic or laminated polycarbonate. Solid acrylic is just as its name suggests – a solid sheet of acrylic either 1-1/4” or 1-3/8” thick depending on the level of protection required. Laminated polycarbonate is made by layering polycarbonate, a heavy-duty clear plastic, between two sheets of glass and laminating it all together. It can be ¾”, 1” or 1-1/4” thick depending on the level of protection. While a bullet will pierce the exterior glass layer of laminated polycarbonate, the inner layers absorb the bullet’s energy stopping it from penetrating through the entire piece of glass.