Able to withstand higher temperatures than borosilicate and almost impossible to scratch, the glass used in the 4th generation Apple iPhone has little need for any kind of protective case, though the gadget freaks will probably buy one anyway.
Apple’s new iPhone 4, unveiled yesterday by Steve Jobs at the Worldwide Developers Conference, includes, among other improvements, one especially fascinating design change for anyone interested in glass: the surface of both the front and back of the phone is made of a highly specialized aluminosilicate glass. By contrast, the back of the previous model of iPhone is coated entirely in a special plastic, while the back of the original iPhone is swathed in a mix of aluminum and plastic. Why the switch from plastic to glass, and why aluminosilicate glass in particular?
The short answer: durability. Apple’s website touts aluminosilicate glass as “the same type of glass used in the windshields of helicopters and high-speed trains” and that it is “20 times stiffer and 30 times harder than plastic”. Indeed, aluminosilicate glass is more durable and even more resistant to thermal shock than borosilicate glass, which is known for its thermal shock resistance. For this reason, it is used to make objects that have to withstand incredibly high temperatures, such as, according to britglass.org.uk, “combustion tubes, gauge glasses for high-pressure steam boilers”, and “halogentungsten lamps capable of operating at temperature[s] as high as 750 C”, or 1382 degrees fahrenheit.
Another view of the glass-encased iPhone 4.
According to the website machinedesign.com, “Aluminosilicate glass (in which some alumina, Al?O?, replaces silica) is another thermal-shock-resisting glass similar to borosilicate but able to withstand higher operating temperatures. These glasses also resist chemical attack and are good electrical insulators. Aluminosilicate glasses are suited for high-performance applications such as high-temperature thermometers, space-vehicle windows, and ignition tubes. Coated with an electrically conductive film, they are used as resistors in critical electronic circuitry. Aluminosilicates cost about three times more than borosilicates and are appreciably more difficult to fabricate.”
Simply from the perspective of durability, Apple’s decision to move to aluminosilicate glass is something of a no-brainer, and a way to stay a step ahead of the numerous challengers to the iPhone’s dominance, especially those phones using the Google Android operating system that seem hot on the heels of Apple’s products. Of course, glass is also a no-brainer when it comes to the look of the iPhone as well — switching from plastic to aluminosilicate glass renders the iPhone 4 smoother, more space-age, and simply sleeker than ever.
—Lee Gaizak Brooks