Many vendors are quick to trumpet the use of Corning's Gorilla Glass
in their products. The glass is used as a protective outer layer for
many devices, from smartphones to large flat panel televisions. But what
makes Gorilla Glass different?
The answer lies in the composition of the glass itself. Most display glass is an alumina silicate formulation, which is made up of aluminum, silicon, and oxygen. The glass also contains sodium ions spread throughout the material. And this is where the difference starts.
The glass is put in a bath of molten potassium at about 400 degrees. The sodium ions are replaced by potassium ions in a process that's a bit like soaking a pickle in salty brine. It's a diminishing process: More of the sodium ions are replaced by potassium at the surface of the glass, and then fewer and fewer are exchanged as you go further into the glass.
Why change from sodium to potassium? Sodium (Na) has an atomic number of 11, while potassium (K) has an atomic number of 19. If you remember your high school chemistry, this indicates that the potassium atoms are significantly larger than the sodium atoms. (The atomic radius of a neutral sodium atom measures out as 180 picometers and potassium at 220 picometers, so potassium measures out as more than 20% larger.)
Imagine that you have a box packed tightly with tennis balls. What would happen if you took out the top layer of tennis balls and replaced them -- one for one -- with larger softballs? The softball layer would be squeezed together much more tightly and it would be harder to get one out.
That's what happens with glass when the potassium ions take the place of the sodium ions. The potassium ions take up more space and create compression in the glass. This makes it more difficult for a crack to start, and even if one does start, it is much less likely to grow through the glass.
The concept of strengthening glass through ion exchange is not new; it has been known since at least the 1960s. And other companies offer glass that has been strengthened by this type of process. Corning's Gorilla brand of strengthened glass has gained considerable market share, however, and has a very visible presence in the marketplace.
The answer lies in the composition of the glass itself. Most display glass is an alumina silicate formulation, which is made up of aluminum, silicon, and oxygen. The glass also contains sodium ions spread throughout the material. And this is where the difference starts.
The glass is put in a bath of molten potassium at about 400 degrees. The sodium ions are replaced by potassium ions in a process that's a bit like soaking a pickle in salty brine. It's a diminishing process: More of the sodium ions are replaced by potassium at the surface of the glass, and then fewer and fewer are exchanged as you go further into the glass.
Why change from sodium to potassium? Sodium (Na) has an atomic number of 11, while potassium (K) has an atomic number of 19. If you remember your high school chemistry, this indicates that the potassium atoms are significantly larger than the sodium atoms. (The atomic radius of a neutral sodium atom measures out as 180 picometers and potassium at 220 picometers, so potassium measures out as more than 20% larger.)
Imagine that you have a box packed tightly with tennis balls. What would happen if you took out the top layer of tennis balls and replaced them -- one for one -- with larger softballs? The softball layer would be squeezed together much more tightly and it would be harder to get one out.
That's what happens with glass when the potassium ions take the place of the sodium ions. The potassium ions take up more space and create compression in the glass. This makes it more difficult for a crack to start, and even if one does start, it is much less likely to grow through the glass.
The concept of strengthening glass through ion exchange is not new; it has been known since at least the 1960s. And other companies offer glass that has been strengthened by this type of process. Corning's Gorilla brand of strengthened glass has gained considerable market share, however, and has a very visible presence in the marketplace.
