How Bullet-Proof Glass Is Made and What Its Layers Do

The name "bullet-proof glass" is misleading: it is not a single material but a sandwich of glass and plastic layers bonded together. Its proper name is ballistic laminated glass. It absorbs a bullet's energy not with one layer but with successive layers that crack and flex one after another.

What does each layer do?

• Outer glass layers: Hard and brittle. They deform the bullet core, blunt its tip and absorb most of the energy by cracking.
• Interlayers (PVB or polyurethane): Bond the glass layers, keep fragments together and spread the impact energy.
• Inner polycarbonate layer: Flexible and extremely tough. It flexes to take the remaining energy and prevents glass splinters (spall) from entering the cabin.

The manufacturing process

1. Glass sheets are cut to the vehicle's window shape and, where needed, bent in a furnace.
2. Layers are stacked with film in a clean room; dust and air bubbles ruin the lamination.
3. The package is held in an autoclave under high temperature and pressure for hours; the films melt and the layers become one body.
4. Edges are machined and sealed, and the glass is prepared with a steel overlap to fit the vehicle frame.

Thickness and weight

Typical thickness is 20 to 22 mm at BR4, 38 to 42 mm at BR6 and around 60 mm at BR7. A sedan's windscreen at BR6 can exceed 60 kg, which is why window motors and door hinges are reinforced.

At İsso Armor every window is produced to the same level as the body panels within the same project, and the overlap zones between glass and steel are tested separately. See our ballistic levels page for details.