In movies, bulletproof glass is as thin as a pencil and repels bullets like an umbrella sheds rain. In reality, bulletproof glasses are quite complicated, and the process behind manufacturing them takes several steps.
So, how exactly is a bulletproof glass made, and what makes them so tough? Read below to find out.
How is Bulletproof Glass Made?
Although bulletproof glass is usually marketed as “bulletproof”, no glass is 100% immune to bullets.
Bulletproof glass is just highly bullet-resistant. How resistant the glass is, depends on how many layers of glass have been sandwiched together with a plastic material called polyvinyl butyral(PVB). For example, to stop a 9 mm bullet, it takes four layers of glass and three layers of PVB, a total of around 3.25 centimeters thick.
Most of the glass is flat and made in an automated system. Here the glass and PVB are heated under pressure to form extremely sturdy material. You might find this kind of glass at a bank’s drive-through window or on the Prime Minister’s limo.
To make bulletproof glass, manufacturers start, ironically, with plains of sheets of plain and highly breakable glass. These large sheets are stored in a glass plant until they are allowed free-fall on a built-in table with an air cushion. Next, a diamond-tipped cutting wheel scores the glass. Then, it goes to the breakout table, where wooden punches snap the glass apart at the points the glass was composed.
After that, a process called seaming occurs. Seaming means that sanding the sharp edges to make a smoother, less jagged surface. These sheets of glass are then inserted into a furnace at 650 degrees Celsius and then cooled for 7 hours. Finally, the sheets are laminated with the PVB, which turns it into a robust single sheet.
What Makes Bulletproof Glass So Strong?
The glass was pressed into different shapes for thousands of years until the Industrial Revolution provided the opportunity to mass-produce plate glass in windows.
In the early 1900s, melting together silica sand, limestone, and soda ash produced glass sheets. Then the glass was poured through rollers that flattened it into a thin ribbon and then treated with heat to increase the glass’s strength. However, the thinness of the glass meant it was still highly breakable.
In 1903, French physicist Edouard Benedictus invented laminated glass made by sandwiching two or more pieces of glass with a cellulose inner layer. Laminated glass, thicker than traditional glass, was used in the windshield of cars to make them safer. The next advance was tempering, a heating and cooling mechanism, which allows the class to harden and break into, curved pieces. Building upon this, in the 1930s, when PVBs became readily available, bulletproof glass was introduced.
What makes bulletproof glass so strong and effective is its thickness. Alternating sheets of glass with PVB in between is what makes bulletproof glass so strong. When the bullet hits the glass, it usually penetrates the first layer of glass.
However, the PVB will provide much more resistance, therefore lessening the impact of the bullet. If the bullet still has any energy left, it will pierce the next layer of the glass, continuing until the bullet is stopped, or passes through the entire obstacle. Even if the bullet passes through, its velocity would be so severely hampered that it would not harm people on the other side of the glass.
If you’re on the lookout for a commercial or auto glass shop in Edmonton, please reach out to us 310-GLAS. At Crystal Glass, we provide you with high-quality products and services at an affordable price. Get in touch with us for a free quote.