Siper Glass Technical Content · October 30, 2026
How Does Bullet-Resistant Glass Work? The Engineering of Laminated Layers
Bullet-resistant glass is not a single material but a system of glass and polymer layers. A general explanation of how each layer meets, spreads and holds the impact.
Short answer
Ballistic glass is safety glass made by laminating several glass plies with polymer interlayers. When a projectile hits the hard glass strike face it deforms and loses much of its energy. The remaining energy is spread over a wider area through the interlayers, and the rear layer limits fragments entering the protected space.
What each layer does
- Strike-face glass: The first surface to meet the impact. Hard glass deforms the projectile and reduces penetration.
- Intermediate glass plies: Number and thickness follow the target protection level; they absorb energy step by step.
- Polymer interlayers: Bond the plies, keep broken glass together and distribute the load.
- Rear layer: A tough material such as polycarbonate limits glass spall on the protected side.
Why is one thick pane not enough?
Monolithic glass behaves in a brittle way and loses integrity when it breaks. In a laminated build the broken plies stay bonded to the interlayers, so the panel stays in place and visibility is not lost entirely. With the right combination of layers, thickness and weight can also be optimised for the same protection target.
How is the protection level defined?
The protection level states which threat the glass was tested against. Weapon type, ammunition, firing distance and number of shots are fixed by the standard. EN 1063 is common in Europe, UL 752 and NIJ in the US, and STANAG 4569 for NATO land vehicles. That a glass meets a given level is demonstrated by a test at an accredited laboratory and its report.
What do "S" and "NS" mean?
In EN 1063, glass classified with the NS (no splinters) suffix releases no fragments from the rear face after firing; with S (splinters), fragments were observed. NS builds are preferred where people are behind the glass.
Other design factors
- Weight: critical for vehicle payload and door mechanisms.
- Optical quality: light transmission and distortion for the driver's view.
- Geometry: curved windscreens, custom cut-outs and gunports.
- Environment: heating, anti-fog and de-icing, temperature changes.
This article is for general information. The performance of a specific product can only be assessed from its test report.
Frequently asked questions
What is ballistic glass?
A transparent protection system made by laminating several glass plies with polymer interlayers and, where needed, polycarbonate, designed against projectile threats.
What sets the number of plies?
The target protection level, the allowed weight and thickness, and optical requirements. The same level can be reached with different build-ups.
What does the polycarbonate layer do?
On the rear face it stops glass fragments entering the protected space and helps reduce total weight for the same protection.
Related products
- Ballistic Glass SystemsMulti-layer ballistic glazing solutions for armoured vehicles and high-security buildings, assessed against each project’s requirements.
- Lightweight Ballistic Glass SystemsBallistic glass builds that address weight targets and spall on the protected side with a polycarbonate inner layer.
Sources
- EN 1063 — Security glazing: bullet attack resistance — CEN
- UL 752 — Bullet-Resisting Equipment — UL
- STANAG 4569 / AEP-55 — NATO