How it works: Ceramic Shield
It’s the toughest glass on any smartphone. So what is it and how does it work?
THE iPHONE 12 range includes a new kind of glass: Ceramic Shield. It’s four times tougher than the glass in the iPhone 11 handsets, and it’s both harder and more scratch–resistant too.
Like most of the smartphone glass in the world, Ceramic Shield was developed in association with Corning of Gorilla Glass fame. What makes this glass different is that it contains tiny ceramic nano–crystals embedded in the structure. Those crystals have a more regular structure than glass, and if you embed them in the right way they can make the glass stronger and more impact–resistant.
You’ve seen ceramics in Apple products before: it’s made several ceramic versions of the Apple Watch. You might also recall that none of those ceramic cases were transparent. That’s because ceramics’ stronger structure means they are usually opaque, which isn’t ideal for device displays; when they’ve been used in phones before by firms such as Samsung they’ve been used to create decorative glass backs, not transparent front screens.
But there’s a middle ground between ceramic and glass called glass–ceramics. Glass–ceramics offer the best of both worlds for screens, combining the transparency of glass with the toughness of ceramics.
According to Corning, glass–ceramics “start life as a glass and then transform into a nearly completely crystalline, or ceramic, substance. This happens under an intense application of carefully controlled heat and the addition of a nucleating agent — silver or titanium, for example — that forms ‘seeds’ around which crystals can grow.” Apple describes this process as a “high temperature crystallization step” and it creates crystals that are so small they don’t impede the transparency.
Glass–ceramic manufacturing is clever stuff that has all kinds of uses; as Corning explains, materials scientists can manipulate the formula to adjust its properties. Some glass–ceramics are great insulators for electronics, others make very effective heat shields for spacecraft. And others stop you from smashing your iPhone — or at least from smashing the front of it. The glass on the back of the iPhone 12 range is still tempered glass.
COULDN’T APPLE USE SAPPHIRE GLASS?
Rumors of sapphire–screened iPhones have been kicking around since the iPhone 6. Back in 2014, Apple announced a new factory with a manufacturing partner, GT Advanced Technologies, that would churn out sapphire screens. But GT quickly ran into difficulties because mass
producing sapphire to Apple quality standards turned out to be much more difficult than it expected and GT went into administration. Apple still uses sapphire glass — it protects camera lenses and it’s in the more expensive Apple Watches — but while sapphire is more scratch– proof it isn’t as drop–resistant as Ceramic Shield. And we suspect even at volume it would probably cost a lot more too.
WHAT ELSE IS INVOLVED IN MAKING CERAMIC SHIELD?
Combining glass with tiny ceramic nano– crystals is a crucial part of the operation, but it’s not the whole process. Corning also carries out a procedure called ion exchange. As Corning puts it: “Glass parts are immersed in a molten salt solution. Potassium ions (electronically charged particles) in the solution migrate into the glass surface, replacing the smaller sodium ions originally in the glass. As the glass cools, the larger potassium ions compress the glass together, creating a compressive stress layer that forms a tough surface.” This creates an extra line of defense against bumps and drops.
IS IT BETTER THAN GORILLA GLASS?
Corning makes both Ceramic Shield and Gorilla Glass, and says Ceramic Shield is the toughest glass in any smartphone. It also says “Gorilla Glass Victus is the toughest Gorilla Glass we have made to date.” Victus is the glass in the Galaxy
Note 20 Ultra, so if Ceramic Shield is the toughest in any smartphone… Corning won’t be drawn further.
SO IS CERAMIC SHIELD AS GOOD AS APPLE SAYS IT IS?
As you’d expect, the first thing the internet tried to do with Ceramic Shield was break it. CNet tried a range of tests including a six–foot drop with the screen side down and then a nine–foot drop, also with the screen side down, and found that the glass survived. The rest of the iPhone, however, wasn’t in great shape. Similar tests by YouTubers smashed the camera. We’ve also seen tests where dropping the iPhone onto its back smashed the glass on both the front and the back simultaneously.
There’s no doubt that Ceramic Shield is much tougher than the smartphone glass we’re all used to. So should you still use a protective case and a screen protector? Let’s put it this way: a two–pack of tempered glass screen protectors is about $10, cases start around that price too. Apple charges $279 to repair the glass on an iPhone 12 Pro. Maybe you should ask yourself: do you feel lucky?