May 2, 2016

Shatter-proof glass isn’t all it’s “cracked” up to be

By Jim Kozlowski Topic: Tech Specs

What’s the difference between tempered glass, shatter-proof glass, and shatter-resistant glass? Absolutely nothing.

Though marketers might sell it with different labels, all of these terms refer to glass that’s been chemically strengthened to avoid shattering. But be careful — that doesn’t mean it won’t break; it means it won’t shatter.

Regardless of what you call it, this kind of glass is strengthened through the tempering process. While there’s no way to make glass unbreakable, tempered glass is the next best thing, which is why it’s important for protecting your phone and your body. Let’s learn how.

Tempered glass can’t shatter but it can still break

Picture a nice beer glass in your hand. Now imagine dropping it on a tile floor. It breaks unevenly, some large pieces and some small. You sweep it up, but inevitably those jagged, teeny-tiny shards get left behind and sometimes end up in your foot. That’s shattered glass.

Now to understand how tempered glass breaks, think of a rock hitting your car’s windshield. It might create a little divot, or maybe a bigger rock makes a spider crack. Either way, your windshield doesn’t shatter and “explode” like the beer glass does. That wasn’t always the case: Back in Henry Ford’s days, a pebble could pulverize an entire windshield.

Part of the reason modern windshields don’t shatter is because they have a laminate layer between tempered glass sheets, binding it all together. While the laminate prevents pieces of windshield from busting apart, the tempered glass avoids the hazard of sharp, dissimilar shards.

So if a weizen and a windshield are both glass, why do they behave differently? It’s because they’re treated differently – chemically speaking.

Regular glass gains super strength through the tempering process

Glass is made by heating sand to a super-high temperature – over 3,200 degrees Fahrenheit. The sand melts, and its crystals reform into a new structure and material.

Tempered glass starts out as regular glass. At Ventev, we get it in big sheets, then score it and break it apart to make our screen protectors. (We also grind the edges and polish it smooth.) Then it goes through the tempering process, which includes three parts:

  • Glass is heated in excess of 700 degrees Fahrenheit.
  • It’s heated in a chemical environment, which changes the chemical composition and structure of the glass.
  • It’s cooled rapidly. An increased rate of cooling makes the outside cool faster than the inside, which helps increase the strength.

That process actually changes the chemical makeup of the glass and creates a new molecular structure inside. When tempered glass breaks, it cracks along the edges of that new molecular structure, rather than shattering or “exploding” like a dropped beer glass.

Tempered glass is like a childhood BFF: You might not pay it much attention now, but it’s there when you need it

The tempering process makes glass much stronger and safer. But it’s expensive, so it’s only used where needed for protection (like with phone screens and screen protectors) or for safety. The most common safety applications are windshields, high-rise building windows, commercial building doors, shower doors, and glass handrails. And if it hasn’t yet occurred to you that this product is absolutely necessary in a zoo, check out what happens when a silverback gorilla body slams a triple-layer tempered glass window.

(Side note: While we’re on the topic of gorillas, Corning’s Gorilla Glass is also tempered glass. It’s not break-proof; it’s shatter-proof. In an ideal world, manufacturers would use the term “shatter-resistant” to label their products to avoid consumer confusion.)

Break your phone’s screen and you’ll have to break the bank to repair it, so add an extra layer of protection to your phone or tablet. Whatever it might be labeled, make sure you have tempered glass screen protection between the world and your device.

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