A downside to polycarbonates is that they are prone to scratches. This scratch potential is why you’ll get a cleaning cloth with eyeglasses or sunglasses you purchase, and why computer and TV screens have special cleaning products, too.

A great article on eHow.com explains how to clean bulletproof glass. Our suggestion: Use a soft cloth (not paper towel!) and a mild soap.

There are two types of bullet resistant glass – solid acrylic and laminated polycarbonate. Solid acrylic is just as its name suggests – a solid sheet of acrylic either 1-1/4” or 1-3/8” thick depending on the level of protection required. Laminated polycarbonate is made by layering polycarbonate, a heavy-duty clear plastic, between two sheets of glass and laminating it all together. It can be ¾”, 1” or 1-1/4” thick depending on the level of protection. While a bullet will pierce the exterior glass layer of laminated polycarbonate, the inner layers absorb the bullet’s energy stopping it from penetrating through the entire piece of glass.

The newest form of bullet resistant glass is one-way bulletproof glass, commonly used in armored vehicles. One-way bulletproof glass is composed of two layers. The outside layer – on the threat side – is made of a brittle glass and the inside layer is a flexible polycarbonate. A bullet that strikes the brittle external layer first causes the glass to break inward toward the polycarbonate layer. The glass breaking absorbs some of the bullet’s energy by spreading the force over a larger area and the flexible polycarbonate stops the bullet.

Bullets shot from the inside of an armored car are able to penetrate the bullet resistant glass because they strike the polycarbonate layer first with more focused energy. The brittle glass layer then breaks outward allowing the bullet to pass through with minor energy loss.

Read “Military wants bulletproof, dimmable windows to protect VIPs” by Mark Rutherford, http://news.cnet.com.

View a slideshow of Cadillac Presidential Limousines dating back to Taft’s presidency and read “Cadillac presidential limousines from Taft to Obama – history and review” by Craig Hover, Kansas City Automotive Examiner.

Bentley is getting in on the security vehicle business with their Continental Flying Spur. For $500,000, it “features military-grade B6-level protection and is fitted with ballistic steel, [ . . . ] bulletproof glass, run flat tires, an explosion-proof gas tank and kevlar flooring.”

Read “Bulletproof Bentley Flying Spur on sale for $500,000,” 4WheelsNews.com.

The government used its first armored car in 1941 with President Franklin D. Roosevelt. After fear of a presidential assassination following Roosevelt’s “Infamy Speech,” the Secret Service used Al Capone’s recently confiscated 1928 Cadillac to transport the president. Capone had outfit the vehicle with “3,000 pounds of bulletproof armor beneath the standard body” and painted it to replicate the existing government vehicles. Read more about Al Capone’s bulletproof car and why the government couldn’t afford to purchase its own. (Image on right taken from FederalTimes.com)

How does one-way bulletproof glass work?

One-way bulletproof glass is composed of two layers. The outside layer – on the threat side – is made of a brittle glass and the inside layer is a flexible polycarbonate. A bullet that strikes the brittle external layer first causes the glass to break inward toward the polycarbonate layer. The glass breaking absorbs some of the bullet’s energy by spreading the force over a larger area and the flexible polycarbonate stops the bullet.

Bullets shot from the inside of an armored car are able to penetrate the bulletproof glass because they strike the polycarbonate layer first with more focused energy. The brittle glass layer then breaks outward allowing the bullet to pass through with minor energy loss.