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What is the Strongest Window Glass?

By October 5, 2022October 19th, 2022Ballistic Glass
Building with the strongest window glass

If you are looking for unbreakable glass, even from missiles or gunfire – we aren’t there yet. And we may never be. However, the safety and security glass industry has grown by leaps and bounds over the last century and we are well on our way to success. But perfection takes time. And once we get there, we’ll wonder if we can do better. It’s the American way.

As with most fortifications, there are levels of “intensity.” Are you looking for protection from gunshots? Blunt objects? Glazing security solutions are often geared towards certain types of attacks. This affords the end-user specific protection from invasions or particular issues.

Almost all glazing security solutions have been tested according to what they claim to deliver. But there are few that can claim they are truly ballistic. Moreover, there are fewer that can be classified as both bullet-resistant and blunt object preventive.

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Security Window Film vs. Security Glass

It’s important to discern between security window film and security glass. Security films are preventative regarding access by delaying a breach. They also hold glass shards together if a glass has been broken with a blunt object. But they don’t deny access altogether.

Security Type/Brand Access Delay Access Denial Bullet Resistant
Security Window Film Yes No No
TRI-SHIELD™ Yes Sometimes No
Riot Glass® Yes Yes Ballistic Options
Ballistic Glass Yes Yes Yes

Security window film is a retrofit solution that strengthens existing glazing. In addition, security window film also helps with access delays. TRI-SHIELD is installed with an aluminum framing that affords additional security in the effort of an attempted breach.

In contrast, security glass solutions (such as Riot Glass and Ballistic Glass), are laminated glass available in various thicknesses for additional layers of protection. Moreover, both are bullet resistant and are more protective regarding explosives. Essentially, they stand up stronger against more abuse.

Laminated glass

Making bullet-resistant glass involves a relatively simple manufacturing process once you have the required materials. Bullet-resistant glass is a form of laminated glass with a plastic coating that is quite effective in stopping bullets. The starting point begins with sheets of glass or acrylic as the base material. Then layers of various types of film are added for additional durability.

The plastic comes in a variety of forms made from different resins, including polycarbonate and polyvinyl butyral, or thermoplastic materials called ethylene-vinyl acetate (EVA) or polyethylene-vinyl-acetate (PEVA), and even acrylic. Polycarbonate is a softer material than acrylic. It’s layered and tends to draw the bullet in like a catcher’s mitt. In essence, softening its impact.

The layers of plastic between the base material are heated causing them to melt and become the adhesive that fuses all the layers together. This provides an additional strength that helps to control shattering and thus, slows the progress of bullets.

The most bullet-resistant glass available on the market is glass-clad polycarbonate. This type of product consists of multiple layers of polycarbonate and security glass laminates layered. The thicker the final product is, or rather the more layers there are, the more bullet resistant it is. However, it’s important to remember that there is no such thing as unbreakable glass.

Layers and levels

Stopping a standard 9mm bullet takes three layers of polycarbonate layered between four sheets of the base material, whether that be glass or acrylic. The larger the caliber of the bullet, the more layers are required. Each layer added of the base material and polycarbonate causes the weight of the bulletproof window you’re making to become heavier. This adds to its strength and durability.

The different levels or grades of protection offered in the U.S. are determined by Underwriters Laboratory (UL) and are described below:

  • Level 1: This is the most common of the protection grades as it provides fortitude against smaller handguns. The majority of crimes in the U.S. that involve a gun use a 9mm handgun. This makes Level 1 products a popular choice for convenience stores, gas stations, pharmacies or retail outlets.
  • Level 2: This is the next most needed level of protection for gun crimes. These products are effective against a larger caliber handgun such as a .357 magnum. It’s ideally suited for protection in banks, financial institutions, as well as high-end jewelry stores.
  • Level 3: This level of protection is effective against .44 magnum handguns. Best used for high-risk and high-occupancy public buildings, level 3 ballistic glass is a popular choice for school and government buildings, as well as police stations and other public facilities.
  • Levels 4–8: The remaining grades of protection (levels 4–8) offer protection against high-powered rifle ammunition and automatic weapons. These are most often used for embassies, high-level government buildings, vehicles or in other military applications.

These are very resilient, thick types of laminated security glass that are incredibly impact-resistant non-glass glazing shields. In other words, it’s tough stuff! However, anything can eventually be penetrated if hit by enough bullets from high-velocity firearms.

How does it work

As stated in the previous section, depending on the rating of a specific glass model, it may be able to stop one or even several bullets. Again, this depends on many factors, including the caliber, velocity, and grain or weight of the projectiles. Ultimately, high-powered ammunition may have no trouble piercing many types of ballistic-grade glass.

After the first round impacts a sheet of bullet-resistant glass, it will significantly diminish in strength with each subsequent impact. Eventually, even the most robust glass can become compromised and no longer provide a protective security barrier. The video below may help you visualize such scenarios.

Key facts about bullet-resistant window glass:

  • Can often resist one or more impacts from high-velocity projectiles, depending on the level
  • Does not immediately shatter, even after repeated high-force impacts
  • Provides multiple levels of protection against varying threat types
  • Classified based on how many and what kind of bullets it can resist from a certain caliber of firearm

There are many types of glass that are not bullet resistant, from the standard annealed or plate glass windows you might find in a commercial building, to the tempered or laminated safety glass commonly used in places where added strength is needed. Simply stated, non-ballistic means that it offers no protection against firearm projectiles.

In other words, if a non-ballistic window gets hit by one bullet, it will likely shatter and fall from the framing. Spall will be dispersed at lightning speed and interior damage will certainly ensue. Certain safety and security glass types are stronger than standard window glass and are designed to be less dangerous when they break, but they are no match for high-velocity projectiles.

In contrast, non-ballistic glass has the following characteristics:

  • Does not provide any protection against firearm rounds
  • Allows all types of bullets to pass through
  • Glass shatters immediately following a gunshot
  • Certain types can protect against different types of impacts, but not bullets

The strongest, almost unbreakable glass

Ultimately, ballistic glass is top-of-the-line protection for businesses and commercial properties. Within that classification, an owner can best determine the appropriate level of protection to fit their needs. It is not “unbreakable glass,” but it’s considered by many as the top tier for security glass windows and doors.

Ballistic windows and doors are one of the premier ways commercial facilities can upgrade their glass to protect against everything from forced entry or burglaries to rioting and looting. It is the closest you can get to unbreakable window glass for your building. Remember, as you search for the strongest glass for your building that if it doesn’t have a ballistic rating, it isn’t bullet-resistant glass.

Finally, there is an important distinction to make here between the glass that is bullet-resistant and glass that is forced entry-resistant. There are many less expensive glass options tested to forced entry standards that can help reduce the chances that a burglar will be successful in forcing their way into your building. However, this doesn’t mean that those options are bullet resistant.

If you would like help in discerning the best security glass for your commercial building or storefront, our experts are standing by to help. We offer a complimentary building perimeter hardening assessment that will leave no stone unturned when providing protection for your building. We can schedule you today!

Defend Your Glass
Hosted by  James Beale
Learn how to protect your building’s weakest points from forced entry, bomb blasts, windstorms, and seismic events.

Feature Photo by w glass – ballistic 


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