Samsung’s Galaxy Z Flip is the first foldable phone with a glass screen. Previous devices like Samsung’s infamous Galaxy Fold featured plastic screens. Bendable glass technology is essential for making better foldable phones and tablets.

Update: Samsung’s “foldable glass” on the Galaxy Z Flip may not be all it seems. But the technology is still interesting, and Corning is hard at work on solid foldable glass. (Samsung didn’t use Corning’s technology, which is still in development and discussed below.)

Foldable Glass Can’t Fold; It Only Bends

“Foldable glass” is a bit of a misnomer. Displays with foldable glass don’t fold all the way—there’s no sharp crease as if you were folding a piece of paper. Instead, the glass bends.

When a device like the Samsung Galaxy Z Flip closes, there’s a gap between the two halves of the glass. There are also raised edges around the screen, which prevent both sides of the glass from directly touching each other when it’s folded shut.

In other words, foldable glass is a type of ultra-thin glass that can bend hundreds of thousands of times without breaking. It can’t fold so that both sides touch.

Bendable Glass Isn’t Completely New

Multiple types of companies are working on this technology. Samsung looks like it’s getting its ultra-thin foldable glass from Korean manufacturer Doowoo Insys, but it hasn’t talked much about the technology.

Corning, which makes the strong, damage-resistant Gorilla Glass used on iPhones and many other smartphones, is hard at work on bendable glass for electronic devices as well. Corning already makes a bendable type of glass named “Willow Glass.”

Bendable glass isn’t entirely new. As Corning’s senior VP of technology for optical communications, Claudio Mazzali told Fast Company that Corning has been bending glass for nearly 50 years. Corning created flexible glass fibers for fiber-optic cables, which he said can bend at a 90-degree angle and continue functioning perfectly.

While bendable glass isn’t new, one of the challenges is making it ultra-thin. Corning’s technology Polly Chu told CNET that “to go to a tight bend radius, you have to go to a glass that’s much, much thinner than what you have today.” The thinner it gets, the more you can bend it.

Making Bendable Glass Work on Phones

Making ultra-thin bendable glass is a big enough challenge, but how do you take that thinner-and-thinner glass and make it as tough and damage-resistant as the Gorilla Glass on current smartphones is?

It’s easy to forget just how impressive Gorilla Glass and similar technologies are: The glass on a modern smartphone’s display can take a beating without shattering or even scratching. Gorilla Glass is harder than common metals. We take that for granted.

John Bayne, who leads Corning’s Gorilla Glass business, explained the challenge to Wired:

Bayne said that Corning is working on keeping the bendability of the glass while improving its damage resistance. He told Wired that putting Corning’s existing Willow Glass through the ion-exchange process that creates strong Gorilla Glass would make the Willow Glass less bendable.

Corning still expects that bendable glass for electronics will be mainstream within the next few years. So how are Corning and other companies solving the manufacturing challenges? That’s the kind of thing these companies won’t reveal publicly. After all, they have a lot of competitors, and the race is on.

RELATED: Hands On with the Galaxy Z Flip: I Only Thought I Didn’t Want a Foldable

Why Foldable Glass Is So Important

In its Galaxy Z Flip reveal video, Samsung says it “made a leap” from polymer (plastic) screens to ultra-thin foldable glass. It’s not just an impressive technological leap. Glass is a better material for a smartphone display.

To bypass the challenges of bendable glass, foldables like the Samsung Galaxy Fold, Motorola Razr, and Lenovo ThinkPad X1 Fold have plastic screens that feel like a plastic screen protector. It probably won’t feel as nice as a glass screen, but that’s the least of your worries. These soft plastic screens are much easier to scratch and ding than glass. Motorola actually says that “bumps and lumps are normal” on its folding Razr smartphone with a plastic screen.

With a glass screen, you won’t have “bumps and lumps” on your display. They won’t scratch and become damaged as easily as plastic, either. That’s why current smartphones—from iPhones to Android phones—have glass touchscreens. Glass is a much more durable material that will hold up better under real-world use. Your fingernail won’t damage a glass screen, but it could easily leave an indentation on a plastic screen.

Are foldable devices the future? Our colleagues at Review Geek certainly think so. Either way, bendable glass is the future of foldable devices.

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