Ballistic Glass and Tempered Glass are Different: Here’s How

22 May 2019
22 May 2019, Comments Comments Off on Ballistic Glass and Tempered Glass are Different: Here’s How

Some naturally occurring forms of glass have been around forever, which may result from volcanic activity, lightning striking sand, and meteorites striking the earth. Glassmaking as a human activity, however, has only been around for about 6,000 years. Today, glass is everywhere around us, from windows of buildings and vehicles to drinking vessels to the lenses many people wear for improving their eyesight. While we tend to think of many objects made of glass as being fragile, technological advances during the last 100 years allow us to make glass that is extremely strong. Tempered glass is much stronger than normal glass, but not as strong ballistic glass that can stop a bullet.

Why Ballistic Glass is Important

When most people think about glass strong enough to stop a bullet, they want to call it bulletproof glass. That’s fine, but it’s not technically accurate because there is probably a big enough gun with a large enough bullet to get through any kind of glass we might make. People who are in the industry would prefer it be called bullet-resistant glass or ballistic glass. 

While some of the highest-end ballistic glass might be considered bulletproof for all intents and purposes, none of it is truly bulletproof. This is fine, though, because the average business that wants to protect its employees from the threat of gun violence during an armed robbery doesn’t need to stop a large bullet fired from a high-powered rifle, it needs to stop what most criminals use, which is a 9mm handgun. Tempered glass is made to withstand some damaging forces, but it won’t be able to protect you against any kind of bullet fired from a gun (except maybe a small BB gun). 

What is tempered glass?

Tempered glass is a kind of safety glass made in a way that makes it both stronger and safer. There are two different ways to manufacture tempered glass. One is called thermal tempering where the glass is heated to temperature of around 1,148º Fahrenheit and then rapidly cooled with forced air drafts, which causes the surface to cool much faster than the interior, resulting in a mix of compressive and tensile stresses. The second way of manufacturing tempered glass is through a chemical toughening process by immersing the glass in a bath of molten potassium nitrate, which forces the exchange of the sodium ions in the glass surface with larger potassium ions. This kind of toughened glass is tougher than thermal tempered glass.

Tempered glass tends to be around four times stronger than regular glass. Just as important, it’s safer when it does break. Why? Because tempering results in compressive stresses in the surface of the glass and tensile stresses in the body of the glass such that when it breaks it shatters into smaller round pieces. Because of the way crack propagation happens in regular glass, it tends to break into large, sharp, jagged shards that are extremely dangerous to anyone nearby the breaking glass. Tempered glass can also withstand cycles of high temperatures much better than regular glass. 

After glass has been tempered, it cannot be further worked in any way, so it must first be cut into its final shape and size before being tempered. Any kind of cutting or grinding tempered glass is likely to cause it to shatter. For some applications, tempered glass may also be laminated with an anti-splinter film that can keep the pieces of broken glass from falling out of their frame or flying everywhere.

The Many Uses of Tempered Glass

One you become aware of how tempered glass is different from regular glass, you begin to see how widely it is used. Perhaps the most common application you might be familiar with is vehicle windows (the side passenger windows and rear windshield are tempered glass and the front windshield is also laminated). But once you start looking around, you’ll see it everywhere.

Around your home you might find tempered glass shower doors, glass tub or shower enclosures, glass cookware, fireplace glass, cabinet glass, glass shelves, glass patio doors and patio furniture, glass tabletops, glass dinner plates, oven door windows, and mobile phone screen protectors. In many different types of buildings, tempered glass may be required by building codes in certain areas and applications where human impact could occur and be dangerous, sliding doors, fire department access panels, elevators, glass installed near swimming pools, glass installed near doorways and stairways, large windows, a skylight, windows extending close to floor level, balcony doors, athletic facilities, and many more too numerous to mention.

Ballistic Glass for Protection from Bullets Isn’t Always Glass

Ballistic glass, also called bulletproof or bullet-resistant glass, is a totally different product than tempered glass, and in many cases is made from entirely different materials. Many types of businesses, organizations, and facilities use ballistic glass to protect their employees from the threat of gun violence. Bulletproof glass, however, isn’t always glass. Transparent bullet-resistant barriers can be made of plastic resins such as acrylic as well as various thermoplastic polymers called polycarbonates. Some transparent bulletproof barriers are made of a combination of materials with a layer of polycarbonate on the outside and a layer of polyurethane connecting it to an interior layer of acrylic. Multiple layers add thickness and strength for higher levels of protection.

Glass-clad polycarbonate is the strongest type of ballistic glass, and is made from various layers of glass, polycarbonate, and PVB, or Poly Vinyl Butyral material. The exterior of glass helps protect from exterior damage, and the alternating layers add up to major protection. Learn more about bulletproof glass fabrication by following this link: How is Bullet Resistant Glass Made? 

Different Levels of Protection Provided by Bulletproof Glass

Ballistic (or bulletproof or bullet-resistant) glass is separated into eight ascending levels of protection. Level 1 has been tested to withstand several rounds of bullets from smaller handguns (9mm and smaller). This is the most common type of gun used to commit crimes such as armed robbery because it’s the most affordable weapon criminals can get their hands on. Levels 2 and 3 are more serious, and able to stand up to larger handgun fire (.357 magnum protection with Level 2 and .44 magnum protection with Level 3 glass). These are used in more secure areas like banks or police stations. Levels 4-8 are designed to handle rifle fire from higher-caliber weapons and are usually reserved for a variety of government and military applications.

Creative Industries: Security Solutions for Today’s World

The world of protective glass and security is as fascinating as it is useful with the many different types of modified glass whether tempered or ballistic, and each has very practical value in a wide variety of settings. At Creative Industries we have been making both standard and custom bullet-resistant glass and related products since the 1970s. We know this industry inside and out and can guide you to the products best suited to meeting the safety and security needs of your business, government building, school, entertainment venue, or sports arena. We invite you to get in touch with us through the contact page of our website or by calling us directly at 800-776-2068 to start the conversation. We’re here to help!