Bullet resistant glass is a fairly modern invention with a lot of interesting uses. While it is marketed as protection against bullets that is only because that’s the most effective metric to properly convey its true properties: shatterproof, strong, and see-through . In truth there are a number of different modern uses for bulletproof glass though admittedly the most common fall under protection, self preservation, and safety.
Bullet resistant glass was first discovered, interestingly by accident, by French chemist Edouard Benedictus. As the story goes while working with a liquid nitrate solution he dropped a beaker which while broken had not shattered. He attributed this interesting find to the thin layer of plastic coating the beaker which would go on to lay the foundation for bulletproof glass of the future. In 1909 Benedictus filed a patent in France for laminated safety glass which was composed of a layer of celluloid between two sheets of glass. From there the story is one of regular innovation until we get to what we see and use today.
Historically war has been the great driver of innovation and this may not be too far from the truth for bulletproof glass as well. During World War I bullet resistant glass was used for the eye holes of gas masks to prevent the glass from shattering or breaking and exposing soldiers to harmful chemicals. Later, in World War II a stronger and bulkier innovated bullet resistant glass was used in vehicles to protect soldiers in trouble areas. From there it’s seen uses for high profile potential targets of assassination. The Popemobile is one example. Bullet resistant glass was used during the trial of Adolf Eichmann in Jerusalem. Additionally all of the windows of the White House were equipped with bullet resistant glass after Pearl Harbor.
How Does it Work?
The basic idea behind bullet resistant glass is a polycarbonate material that is layered between two ordinary panes of glass in a process of lamination. Polycarbonate is a basic tough and flexible plastic that you might know by some of its brand names: Lexan, Tuffak, or Cyrolon. All bullet resistant glass uses two panes of thick glass because the first is designed to absorb the initial impact and distribute the force among the flexible plastic between the two panes so that the projectile doesn’t have enough energy to make it through the second pane. Bullet resistant glass because of its multiple layers is usually at least 4 inches thick but may be thicker depending on what power of rounds it needs to be able to stop.