How It Works: Strengthening Glass | Science of Glass | Corning

How It Works: Strengthening Glass

How It Works: Strengthening Glass

Strengthening glass with ion exchange

Corning® Gorilla® Glass redefined the toughness and durability of consumer electronics. Thanks to this cover glass, which has been featured on more than 8 billion devices, consumers have thinner, sleeker devices with exceptional damage resistance to the scratches and bumps of everyday use. What's more, Corning keeps making Gorilla Glass more damage resistant and proving its use in a growing number of applications – from elevators to vehicles.

Gorilla Glass gets its damage resistance from Corning's ion-exchange process for strengthening glass. But, how does that work?

First – it is essential to understand why glass cracks or shatters. Glass will break from flaws on its surface. These flaws will propagate when there is tension on the glass. The ion-exchange process for strengthening glass essentially puts the surface of the glass in a compressive state helping to resist the tension that occurs during damaging events.

In the process for strengthening glass, Corning first uses its trademark fusion process to manufacture a pristine glass sheet. This glass then soaks in a molten salt solution. Potassium ions in the solution migrate into the glass surface, replacing the smaller sodium ions within the structure of the glass. These larger potassium ions create a compressive stress layer that forms a tough surface.

"The surface toughness you create by chemically strengthening glass provides an ideal cover for touchscreens, mobile devices, and other heavy-use applications." - Jonathan D. Pesansky, business technology director, Gorilla Glass

"It's useful to imagine another scenario that illustrates this concept," said Pesansky. "A triangular billiards rack holds 15 pool balls closely together, but still with plenty of room to roll within the rack. Replace those balls with slightly larger tennis balls, and the rack will be packed too tightly for balls to roll (illustrating the effect of compression). Its surface, in effect, has become resistant to rolling through the compression of the tennis balls."

Why it matters

This process, combined with Corning's proprietary glass compositions, enables glass to retain more of its strength even after a minor nick or scratch, protecting it from more cracks and flaws. The super-tough surface created by the ion exchange process provides the first line of defense against everyday hazards such as dropping a device on rough streets, sidewalks and parking lots.

Corning’s glass scientists are constantly stress-testing glass and improving both compositions and chemical strengthening processes like ion exchange. Their deep understanding of the material science and damage mechanics of glass are likely to yield even more remarkably tough glasses in the future.