Gorilla Glass Explained…

The below article was submitted by Casey (@oka_xda on Twitter). If the name sounds familiar – he is the guy who sent me his phone overnight when I was without one. This guy rocks. He recalled that I have an open invite to readers – use this blog as your own. You have something to say, type it and email it to me. All I ask, be useful. Casey has gone above and beyond. Please let him know that you appreciate this information.

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You all have heard of Gorilla glass (been around since the early 1960’s) but what makes it different ? Basically Gorilla glass is a glass that is stronger and more flexible than normal glass. Normal glass is usually made with pure sand with added soda/lime as the stabilizer/fluxer/formers. Modifying this process allows Gorilla glass to be thinner more flexible and stronger.

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Basically, Gorilla has a harder surface than normal because of the Annealing process (heat and cooling process to relieve stress in the glass and make the surface a harder surface) and the chemical treatment during the annealing process.

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Gorilla glass starts by combining pure sand (silicon dioxide) and other types of chemicals (see below the fluxers, formers, and stabilizers) but the resulting glass is called aluminosilicate, which is stripped of impurities and melted down. The molten glass is then sent to molds it fills up and actually overflows on each side. During this (fusion draw) process, in a controlled fashion, the robotic arms pull down on the glass until it is a constant .59 millimeter-thick sheets of Aluminosilicate Glass.

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Once this is completed, you have very big sheets of clear, clean, pure glass, but it isn’t much stronger than regular glass. Gorilla glass gets its strength through the following interesting chemical process.

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Corning dips each sheet into a molten salt bath where a chemical exchange occurs. Potassium ions are infused into the glass. At the same time, sodium ions exit the glass. The potassium ions are larger than the sodium ions. This pressure creates what’s called “compressive stress.” That stress is actually a good thing and stops the glass from breaking on flaws.

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Because of the process it makes Gorilla Glass Ideal for cell phones and alike because:

1. It is lighter because it can be thinner
2. Its surface is harder than traditional glass so it is more resistant to scratches.
3. If has a greater modulus (more elastic) so it can take more flexing without failure.

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Of the 3 above, weight is the major driving force for the Gorilla Glass use in a cell phone. Samsung and Apple use Gorilla glass on all their phones/tablets to make the products lighter.

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Below, for you techies types are the basic short explanations of the glass additives and quenching.

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Quenching: The act of taking something (steel, glass) from one temperature quickly to a lower temperature. It is a way to increase surface hardness, increase flexibility or both. Traditionally, this was done by heating something up and then dipping into a bath of oil or water. The act causes the molecules to become aligned  making the material have improved properties. Typically, they used Salt brine, oil, Air, or water. Nowadays, the modern systems uses a combination of 2 of the aforementioned and adds chemicals to better control the process.

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Formers: are the basic ingredients. Any chemical compound that can be melted and cooled into a glass is a former. Silica (sand) is the most common former.

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Fluxers: help formers to melt at lower, more practical to achieve temperatures (1300°C or 2370°F). Fluxes include Soda Ash, Potash, and Lithium Carbonate. However fluxes make the glass chemically unstable. Therefore;

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Stabilizers:  combine with formers and fluxes to keep the glass uniform and keep its special structure intact. Stabilizers include Limestone, Magnesia, Barium Carbonate, Stronium Carbonate, Zirconia, and more.

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Additional Oxides: are used to impart color, for example cobalt oxide turns a melt deep blue; iron or chromium oxide turns it green; gold changes it to a light red. Other oxides are used to decolorize, opacify, or control important characteristics such as expansion rates and optical properties. Coating can be added during this time to improve the color vibrancy of the LCD as well as to reduce the UV and glare of ambient light.

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Here is a video showing the strength of Gorilla Glass (note the Samsung name there):

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Thanks,
Casey!