Bullet proof glass or bullet resistant glass refers to any type of glass that is built to stand up against being penetrated by bullets. Although the public uses the term ‘bullet proof glass’, generally within the industry itself it is referred to as bullet-resistant glass, because there is no feasible way to create consumer-level glass that can truly be proof against bullets.

Bullet proof glass is usually constructed using a strong but transparentmaterial such as polycarbonate thermoplastic or by using layers oflaminated glass. The desired result is a material with an appearance and light-transmitting behavior of standard glass but offers varying degrees of protection from small arms fire.

The polycarbonate layer, usually consisting of products such as Armormax, Makroclear, Cyrolon, Lexan or Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet proof glass is usually 70–75 mm (2.8–3.0 in) thick.

Bullet proof glass constructed of laminated glass layers is built from glass sheets bonded together with polyvinyl butyral, polyurethane or ethylene-vinyl acetate. This type of bullet proof glass has been in regular use on combat vehicles since World War II; it is typically about 100–120 mm (3.9–4.7 in) thick.

Working Principle of the Bullet Resistant Glass

In the bullet proof glass, the Laminate-layers of tough plastic called polycarbonate sandwiched in between the pieces of toughened glass make the glass ten times thicker than the ordinary glass and it is very heavy. If someone fires a bullet at an ordinary piece of glass, the glass can't bend and absorb the energy. So the glass shatters and the bullet carries on through with hardly any loss of momentum. That's why ordinary glass offers no protection against bullets.