Aluminosilicate compositions like Gorilla Glass contain silicon dioxide, aluminum, magnesium, and sodium. When the glass is dipped in a hot bath of molten potassium salt, it heats up and expands. Both sodium and potassium are in the same column on the periodic table of elements, which means they behave similarly. The heat from the bath increases the migration of the sodium ions out of the glass, and the similar potassium ions easily float in and take their place. But because potassium ions are larger than sodium, they get packed into the space more tightly. (Imagine taking a garage full of Fiat 500s and replacing most of them with Chevy Suburbans.) As the glass cools, they get squeezed together in this now-cramped space, and a layer of compressive stress on the surface of the glass is formed. ... (T)he “stuffing” or “crowding” effect in chemically strengthened glass results in higher surface compression (making it up to four times as strong), and it can be done to glass of any thickness or shape.
- Gorilla Glass has at least two cousins, “Willow” and “Lotus”: Lotus Glass is a partnership between Corning and Samsung to create durable glass for next-generation organic light-emitting diode (OLED) displays. That’s playing the long game, as more monitors and phones move toward the lower-power, constantly evolving OLED field. Then there’s Willow Glass, which, while something of a different product, definitely owes its existence and touch-sensitive focus to the success of Corning’s collaboration with Apple on the big Gorilla Glass bake-off.