Bullet proof walls are a vital part of any bullet proof system. Inch-thick acrylic windows and stainless-steel counters, cash-trays, and frames aren’t worth much if they’re bolted to a wall that can’t stop a shot from a .22 squirrel rifle.
What people commonly call “bullet proof walls” are really “bullet resistant.” Such walls are made from materials that have been tested and rated by independent agencies who verify that the material can stop a specific number of shots from a specific caliber firearm. For example, a Level 4 bullet proof panel will stop a bullet from a .30-06 hunting rifle, while a Level 7 panel will stop five shots from an M16.
To these standards, some materials are natively “bullet proof”: a foot-thick concrete wall or two inches of solid steel will withstand many shots from a handgun, sub-machine gun, or rifle. But in most cases building contractors can’t do an entire job in poured concrete and heavy steal slabs; they need to rely on existing or easily constructed stud walls made from light wood or metal frames and sheets of dry wall.
Bullet Resistant Fiberglass
For practical purposes, the key to building a bullet proof wall is bullet resistant fiberglass (also called “opaque armor”). Fiberglass is a two-part laminated material made from plastic reinforced with synthetic fibers. The material is lightweight, strong, and although it is rigged once it dries, it can be easily molded into any shape during production (and is thus popular for boat hulls and auto body panels). The fiber at the heart of a bullet resistant fiberglass panel is a super-tough synthetic mesh of DuPont™ Kevlar® fiber (this is the most familiar brand name for this family of ultra-durable fibers, although that specific brand of bullet resistant fiber is only occasionally used in modern bullet proof panels). Ballistically rated fiberglass panels are thus often called “Kevlar panels.”
The Birth of Kevlar
Developed in 1965 by DuPont, Kevlar was originally used to replace the steel and cloth belts in race car tires. The material itself is a woven synthetic para-aramid fiber (similar to nylon). DuPont had already invented several related aramid synthetic fibers, including Nomex (which is still used to produce fire-resistant garments for firefighters and test pilots). Kevlar shares Nomex’s lack of a melting point and near complete fire-resistance. But in contrast to Nomex or nylon, when Kevlar forms into fibers, its molecules naturally align themselves into long, unbroken chains along the fiber’s entire length. Subsequently, in addition to its fire-resistance, Kevlar is also highly resistant to abrasion and shows incredible tensile strength–making it perfect for catching bullets.
Kevlar Panels in Action
Bullet resistant fiberglass panels are made by saturating the Kevlar-like mesh with resin. Flat layers of this resin-soaked mesh are then squeezed and baked by an industrial press. The result is a hard, dense, rigid panel. When striking one of these panels, a speeding bullet deforms, loosing much of its momentum. The layers of resin-caked mesh separate, unfolding like an accordion’s bellows, absorbing even more of the bullet’s energy. The practically unbreakable strands of Kevlar enmeshed in the panel do not permit the bullet to pierce through, and instead catch and deflect the projectile, like the walls of a bating cage shrugging off a hard line drive.
A bullet resistant panel just 1/4-inch thick can stop at least three 9mm bullets fired dead on from just a few feet away. Need to stop a larger bullet? Just laminate on more layers of Kevlar and resin during the production process, or layer up the panels themselves during installation.
Building Bullet Proof Walls
Contractors looking to build bullet proof walls start by framing a standard stud wall. They then mount bullet resistant fiberglass panels on the studs, making sure to double-over all seams with additional strips of fiberglass. Finally, the contractor covers the fiberglass wall with drywall or paneling. The resulting bullet proof wall can be finished just like any conventional wall: painted, wallpapered, decorated with framed landscapes or advertising. It’ll stop bullets as well as a bunker, but to any passers-by it’s indistinguishable from a standard wall.