The term Ion-Strengthened Glass refers to a method to chemically increase the hardness of a piece of glass by heating the glass and exchanging Sodium ions in the glass with Potassium ions brought by a bath of potassium salt.

Because the Potassium Ions are bigger, it makes the glass stronger when the glass cools down. This is a process largely used in the glass industry “Chemical Glass Strengthening” name


*Illustration courtesy of

One of the benefits of chemical strengthening vs. heat treatment is that the temperatures involved are much lower, which allows the strengthening  to happen without any optical distortion. This is arguably extremely important if the glass is to be used to protect a multi-million pixel display.

High-profile glass companies a derivative of this technique, including Corning (Gorilla Glass) which holds patents on the matter.

The term “Ion-Strengthened Glass” was used by Apple during its iPhone 6 keynote on Sept 9 2014.

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