How Gorilla Glass protects your phone

In theory, at least, using glass for the screens of mobile devices seems like a very bad idea. It's heavy, and regular wear and tear means whatever you're looking at will quickly become obscured by a mass of criss-crossing scratches and chips.

Then it will inevitably break, requiring an expensive replacement, before the whole process starts all over again.

None of this is exactly a recipe for technical success, and so it's hardly surprising that many computing hardware manufacturers initially opted for lighter, more flexible plastic screens, instead.

There are some interesting alternatives, though, and perhaps the most successful is Gorilla Glass. Produced by American manufacturer Corning Incorporated, it's a chemically strengthened glass which can be as thin as 0.4mm - less than four times the thickness of the human hair - while remaining scratch and impact-resistant.

And it's a mix which has seen the product used to protect more than 1.5 billion devices worldwide, including Samsung's Galaxy phones and tablets, Sony Bravia TVs, laptops from big names like Acer, Dell, HP and Lenovo, and even the iPhone at one point (although with neither Corning nor Apple talking, whether this is still the case isn't entirely clear).

How has one company achieved such success? It takes a little work, starting with the way the glass is formed in the first place.

Fusion draw

Gorilla Glass starts its life through Corning's fusion draw, a proprietary process which helps ensure the product is both thin and exceptionally pure.

The glass material itself is a high quality, but relatively conventional aluminium, silicon and oxygen mix - a regular alkali aluminosilicate blend - which is heated until it's molten. In the past this might then have gone through a float glass process, where it's poured onto a bed of molten metal (often tin), flattening under its own weight, then cooled until it becomes a sheet.

Fusion draw, though, sees the material poured into a long v-shaped trough called a refractory isopipe. This overflows, running down either side of the trough, rejoining at the bottom to form a single sheet of glass. This simple process helps to keep the product very pure (regular float glass has a layer of tin oxide on one side).

There's also no need for polishing, something which can itself introduce and exacerbate flaws in the glass. And the end result is a product so pristine that Corning says "a rejectable particle is comparable to a single mustard seed on a football field".

This is a great start, resulting in very thin and exceptionally clear glass. The lack of defects and unwanted particles also helps to ensure it's as strong as normal glass can be. But it is still just normal glass, unfortunately - transforming it into Gorilla Glass requires another important step.

Ion exchange

With fusion draw complete, the material produced so far is cut down to size and then placed into a 400 degree C bath of molten salt. This is all part of a process called ion exchange, a standard purification technique in many industries, but here the extreme heat is used to draw out sodium atoms from the surface of the glass, replacing them with larger potassium atoms.

Talking about swapping "smaller" and "larger" atoms may sound rather irrelevant, but it does make a very real difference. The end result is a surface coating which is far more compressed at the atomic level, making it significantly more resistant to scratches.

What's more, while regular glass has a major problem with crack propagation - the way defects will spread and grow - Gorilla Glass's state of permanent compression means the material is always pushing together, which means it's far less likely to experience any cracks in the first place.

This doesn't make the product invulnerable, of course. Hit your screen hard enough, perhaps with another hard material, and you'll still be in trouble (it's damage "resistant", not "proof").

Gorilla Glass will already perform far better than regular glass, though, and many other materials - and this is just the start. Corning has plenty of other interesting developments planned for the future.

Gorilla Glass everywhere

Strengthening glass is a good first step, but it's not the only area of the material which needs a little "help".

David Velasquez, Corning Director of marketing and commercial operations told us: "Consumers increasingly want solutions to other cover-glass related problems like outdoor reading, smudges, and germs. We are working on all of these and are very excited about progress we are making."

It seems like that progress is significant, too, with Corning Vice President Jeffrey Evenson claiming at the recent MIT Mobile Technology Summit that an upcoming anti-microbial treatment can greatly resist bacterial build-up, while a new anti-reflection technology should ensure Gorilla Glass is tens of times more transparent than purified water.

Why stop with touch and mobile devices, though? Evenson also revealed plans to branch out, in particular by replacing some of the glass used in car windows.

Thinner, stronger and more scratch resistant glass doesn't just bring safety benefits, he pointed out: it also reduces vehicle weight and lowers its centre of mass, so helping to improve fuel economy. Apparently the first cars with at least some Gorilla Glass will be available within the next year.

For all its success so far, Gorilla Glass may have some formidable competition on the way. For instance, companies such as Samsung and LG are working on plastic screens, due imminently, which can be bent, folded and twisted without breaking, and are lighter than Corning's products.

Whoever wins, the future for mobile device screens is looking brighter - and clearer, stronger and less reflective - than ever.