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How does bulletproof glass work?

The fascinating science behind ballistic and armored glass goes back to two breakthroughs. In the first, an unknown scientist discovered in 1625 that glass objects made by putting molten glass into cold water were hard enough to withstand a hammer’s blow. These curiously tough glass beads were known as Rupert’s Drops, as they were introduced to Britain by Prince Rupert of the Rhine in 1660. The second historic milestone was an accidental discovery by French chemist and painter Edouard Benedictus in 1903. Benidictus dropped a glass beaker coated with cellulose nitrate to find that it cracked, but did not shatter. Today, different types of security glass including bulletproof glass use multiple layers of glass and other materials to dissipate the force of impact and maintain material integrity.

The physics of bullet resistance

The impact of a projectile on a fixed object is a complex physical phenomenon. This is especially true of glass, as its behavior on entry and penetration is completely different from that of other materials such as metal or wood. Glass breaks at speeds of several thousand meters per second (approx. 10,000 km/h), far faster than the speed of a bullet, which is generally several hundred meters per second. For example, a projectile of 7.62 x 51 caliber, fired from a NATO G3 rifle, travels at around 1,000 m/s (approx. 3,600 km/h). This means the formation of fissures in the glass caused by the impact of the bullet outpaces the bullet, dissipating the resulting energy. 

Once impacted, however, glass loses a great deal of its resistance. This is why conventional bulletproof glass consisting of multilayered glass only is less bullet resistant than more sophisticated combinations of materials. SILATEC constructs bulletproof glass using alternating layers of hardened glass and highly advanced transparent synthetic compounds such as polycarbonates selected for properties like extreme toughness, elasticity and hardness. The result is unsurpassed resistance to penetration by the vast majority of projectiles – and peace of mind based on industry-leading technology.

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