It’s entirely possible that before Monday you hadn’t heard of GT Advanced, a New Hampshire based materials manufacturing firm. (We hadn’t.) But now, with news that Apple is partnering with the firm to open a Sapphire Glass plant in Arizona, we take a peek at how Apple will go about making sapphire glass for use in cameras, and possibly screen for its popular iOS devices.
The process is relatively straightforward: a sapphire seed, about the size and shape of a hockey puck, is placed at the bottom of a single-use molybdenum barrel called a crucible. The crucible is then filled with a mixture of condensed corundum -a crystalline form of aluminum oxide- and a material called “crackle,” sapphire material left over from previous runs. The full crucible is then placed inside the furnace, where it sits atop the “finger,” a small liquid helium-cooled platform that prevents the sapphire seed from melting too early. The furnace is sealed, the air is evacuated, and the temperature is brought up to 2100 degrees Celsius to allow the materials to melt together. (The video says 2200, but that’s wrong. It’s 2100, for all you making-sapphire-at-home hobbyists.) The material is put through a series of cooling cycles over the next 16 or 17 days, during which time the sapphire slowly crystallizes from bottom to top. The end result is this: a 115kg cylindrical section of industrial sapphire called a “boule.”
Pocketnow visited the GT Crystal Systems facility in Massachusetts and saw how sapphire glass is created. It’s a fascinating process, as the above video shows.
Apple currently uses sapphire glass – in a smaller form factor – to protect the camera on its iPhone, and also on the new Touch ID-enabled Home Button on the iPhone 5s. Various rumors have floated that Apple will in the future be using sapphire glass for its iOS device screens in the place of the current Gorilla Glass from Corning, a rumor that certainly won’t be going away any time soon, now that the company will be building a sapphire glass production plant in Mesa, Arizona.