iPhone X: how can a glass phone be so durable?

November 28, 2017

The release of iPhone X this year marks the 10th anniversary of the iPhone – a milestone which also marks a decade of our ability to drop our precious devices in the stupidest of places. Type ’smashed screen’ into Google and you’ll see over 5 million pages; IT HAUNTS OUR VERY DREAMS.

Thankfully, we saw the solution in 2007, too: the introduction of Gorilla Glass. And its latest evolution is the answer to our prayers.

Gorilla Glass was, at the time, a revolutionary substance that allowed users of the first iPhone to get their heads around using a touchscreen (on a phone? *faints*) without leaving massive fingerprinty smears. This version was 1.4mm thick, and minimised damage from dropping the device and scratches from everyday contact with whatever was in our pockets.

A decade and nearly 5 billion devices (including phones, tablets, TVs and smart watches) later, and the 5th incarnation of Gorilla Glass is said to be twice as strong as the 4th version.

It can survive 1.6m drops (selfie height!) 80% of the time. And it can be manufactured as thin as 0.4mm – just under 4 times the thickness of a human hair.

And it makes up the majority of the exquisitely designed, bezel-free iPhone X.

And with the toughest glass ever used in a smartphone, the new iPhone 11iPhone 11 Pro and iPhone 11 Pro Max have followed suit.

So what the heck is Gorilla Glass?

Gorilla Glass is the brainchild of Corning, an American industrial manufacturer. They’d been experimenting with chemically strengthened glass as far back as 1960, when they were looking into durable windows and screens for airplanes, racing cars and slightly less sexy industrial use. (Sidenote: this was called ‘Project Muscle’, and now we want to give all our projects cool codenames.)

But then the smartphone came along, and with it Gorilla Glass’s true calling.

How is Gorilla Glass made?

When you look at how Gorilla Glass is made, the glass itself isn’t actually the star of the show – though its construction is pretty special.

The molten glass is poured to overflowing into a trough with a little pointy bottom, so when it drips over the edges it converges at this point and drips downwards in a perfectly flat plane of glass. This immediately makes the glass stronger, as it doesn’t need polishing – a process that creates weaknesses and flaws in its makeup.

But the real MVP of the manufacturing process is the chemicals. The freshly formed sheet of glass gets lowered into a bath of molten alkaline potassium salt, at temperatures reaching 400°C (750 °F).

Why? Well, there are ions in the glass – particles of matter with a tiny electric charge in each one. The ones already in the glass are sodium, and are quite small. The salt bath has larger potassium ions in it, and their charge makes them rush into the glass, kicking out the weedier sodium ions as they muscle in.

Because they’re bigger, they have to squish in harder – which makes the surface layer of the glass compressed and therefore more solid. This surface is what resists scratches and cracks.

So what does this mean for the iPhone X?

It’s always wise to remember that Gorilla Glass 5 is damage-resistant, not damage proof. It greatly lowers the odds of disaster when you drop your phone somewhere unforgiving. Don’t go testing it with hammers though. It’s always wise to invest in a case, too.

But if you remember how previous devices broke your heart when you broke their glass, rest easy friend: Gorilla Glass 5 is a leap ahead from what you might think you know.