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The Secret To Making Ultrastrong 'Gorilla Glass'


This is SCIENCE FRIDAY, I'm Ira Flatow. How many times have you dropped your smartphone on the ground? Ew. You pick it up, and voila, wow, not a crack to be seen. Now, I know some of you also found out that the glass is not totally unbreakable, but still the glass protecting your screen is a heck of a lot more durable than the run-of-the-mill stuff in baking dishes and wine glasses.

It's called Gorilla Glass, and it's on 750 million devices worldwide, maybe even in the one in your hands right now. How does it hold up to all that abuse, avoiding scratches and chips and nicks? And how do they make it ultra-strong? It's even less than a millimeter thick. How do they do that?

Here to talk about it is Dave Velasquez. He is director of marketing and commercial operations for Gorilla Glass at Corning Incorporated in Corning, New York. He joins us by phone. Welcome to SCIENCE FRIDAY.

DAVE VELASQUEZ: Hello, Ira, good afternoon.

FLATOW: Hey there. Who came up with the name Gorilla Glass?

VELASQUEZ: Well, about five years ago, when we started the project, it was actually the internal project name, and we had a series of scientists and engineers trying to think about how we could make glass tougher, more resistant to damage. And someone in the room just threw it out and said gorilla, and it stuck, and it became the product name.

FLATOW: And tell us about the history. Wasn't Corning experimenting with a super-tough glass back in the '60s?

VELASQUEZ: Yeah, we sure were. Back in the early '60s, we had a product that we actually launched called Chemcor. The basic principles of trying to strengthen glass were the same, but we were targeting different applications to include automotive and safety glasses.

FLATOW: And so why is it not in automotive and safety glass?

VELASQUEZ: Well, a couple of reasons. Back then, we really couldn't get the costs down appropriately for the automotive industry, and design cycles are quite long. And you combine that with - if you think about in a windshield, the things that - the way you want to have a windshield break really ties to the safety for the inhabitants, and this glass was very strong, and really, you couldn't get it to break in the proper way.

FLATOW: So you would break your head before you would break the glass.

VELASQUEZ: That's a little oversimplification, but that's - basically we couldn't get through the safety qualifications in the design cycle.

FLATOW: How do you take glass and make it into Gorilla Glass?

VELASQUEZ: Well, you start with a basic alumina-silicate based glass - again, we make this pretty thin, under one millimeter, and once the glass has been worked on and formed into a part that goes onto a device, it's actually dipped into a bath of molten salt. And this process is called ion exchange.

This molten salt is made up of potassium nitrate, and through basic diffusion, potassium ions in the salt bath diffuse into the glass and kick out sodium ions that are in the glass. And the best way to describe it, if I can visualize it for you, is think about a coffee can full of marbles. And those marbles are sodium.

Now take a handful of them out and put an equal number of marbles that are about - are bigger, and force them into that same coffee can and seal it. And you can think about the pressure that you have to put on that coffee can to put those larger marbles into the can.

Well, that's what happens at the surface of the glass. So the surface of the glass is put under compression because the potassium ions are physically bigger than the sodium ions that have left the glass.

FLATOW: So there's a lot of pressure or tension inside the glass?

VELASQUEZ: It's - we call it compressive stress, right, and so that compressive stress literally forms, like, an armor near the surface of the glass that A) helps prevent flaws from occurring, and when these flaws occur, it prevents them from propagating and turning into a failure.

FLATOW: Is that why when it does break, it breaks so spectacularly, because of the pressure in there?

VELASQUEZ: Right. No, you hit it right on. The - no glass is unbreakable, certainly, and when you strengthen the glass this much, there's tremendous compressive stress put in the surface of the glass. So when you do actually manage to break it, that kind of force, the energy that's stored in the glass causes it to shatter, like you say, pretty impressively.

FLATOW: So you make the glass itself in upstate New York there at Corning. And then you have to ship it to China for them to put it in the phones.

VELASQUEZ: We make the glass. We don't make it here in Corning, New York, we make it in plants around the world. We have a plant in Kentucky and Taiwan and Japan. And yes, we make large sheets of this glass, and then we put it into crates, and then we ship it to companies called finishers, most of them are in China, and those are the companies that actually cut the glass into the pieces, drill holes, polish, et cetera, into the shapes of the parts that go onto the devices.

FLATOW: Why can't you - I'm sorry, why can't you make it the shape itself beforehand?

VELASQUEZ: Well, it's much cheaper, more effective, to make these large sheets of glass and then cut it later, as opposed to trying to mold - or mold from molten glass into a small part.

FLATOW: It's not having to do with maybe the glass being too tough or brittle to work with at that point?

VELASQUEZ: No, that's a good question, but we - the chemical strengthening process actually happens after our immediate customers have cut the parts down to the size, the shape of the parts.

FLATOW: There's a famous story in Walter Isaacson's biography of Steve Jobs that says he actually came down at one point and demanded that Corning make him some glass for his - any truth to that?

VELASQUEZ: Well, the story, we certainly, we don't comment in detail about the relationship with different customers, but the story is there in the book, and it's true.

FLATOW: Is there other kinds of products, now that you've discovered how popular and ubiquitous the Gorilla Glass could be - any other places we might see it showing up?

VELASQUEZ: It's a really exciting time for us, Ira, to - it's only five years in, and it's been a tremendous success story for the company. Handsets really have taken off. We're at a point now where almost half of all handsets in the world made are smartphones with some type of touch capability.

And then I'm sure you know of tablet computers, are very exciting, have grown quite magnificently in the last few years. And the market is starting to think about expanding touch interfaces with the different devices. If you think about your laptop computer, for example, or monitors or tabletops, even the front of a refrigerator, there's a lot more applications out there, we feel.

We feel that touch and the interface of touch is only going to grow.

FLATOW: Do you have to design and engineer the glass specifically to be touched as a utility?

VELASQUEZ: We don't design the composition of the glass specifically for touch. You know, there's some basic principles that we have to adhere to, to enable the touch capability within devices. We engineer the glass primarily to make it as damage-resistant as possible, and therefore the different types of materials and the density of materials and the composition are really optimized so that we can chemically strengthen it to its optimal and utmost potential.

FLATOW: All right, Dave Velasquez, thank you very much for taking time to talk with us.

VELASQUEZ: OK, thank you, Ira.

FLATOW: Dave Velasquez, director of marketing and commercial operations for Gorilla Glass. That's at Corning in Corning, New York. Transcript provided by NPR, Copyright NPR.