While both are types of security glazing, "bullet-resistant" and "blast-resistant" glass are engineered for fundamentally different threats and thus have different constructions. Bullet-resistant glass (more accurately called transparent armor) is a laminate of multiple layers of glass and polycarbonate. The glass layers are hard and break the bullet, while the polycarbonate layers are ductile and hold the broken glass together, absorbing energy and preventing spall. The thickness and number of layers are calibrated to specific ballistic threats (e.g., handgun, rifle). Blast-resistant glazing is designed to withstand the overpressure and impulse of an explosion. Its construction also uses lamination, but it prioritizes the flexibility and tensile strength of the interlayer (often a thick, specialized polyvinyl butyral (PVB) or ionoplast) to keep the entire unit intact as it deforms under pressure. It is designed to remain in the frame to protect occupants from the overpressure itself and from being ejected from the building, rather than just stopping projectiles.
Core Knowledge:
Bullet-Resistant (Projectile Focus): A laminate of glass and polycarbonate. The glass breaks the projectile, the plastic absorbs energy and contains spall. Rated by ballistic level (e.g., UL 752).
Blast-Resistant (Pressure Focus): Uses thicker, more flexible interlayers (e.g., PVB) to allow the entire window unit to flex and absorb the energy of a shockwave without breaking out of the frame. Rated by pressure and impulse (e.g., ASTM F2248).
Different Failure Modes: Ballistic glass is designed to stop penetration. Blast glass is designed to remain intact and in the frame while deforming.
Application: Ballistic glass is for checkpoints, vehicles. Blast glass is for government buildings, embassies, and high-risk facilities.
