kottke.org posts about glass

The story of how Gorilla Glass came to beSep 24 2012

Gorilla Glass is the thin strong glass used for the screens of most smartphones. It was invented in the 1960s by Corning but was shelved in the early 1970s due to a lack of demand. The iPhone brought it out of retirement in a big way.

Chemical strengthening, the method of fortifying glass developed in the '60s, creates a compressive layer too, through something called ion exchange. Aluminosilicate compositions like Gorilla Glass contain silicon dioxide, aluminum, magnesium, and sodium. When the glass is dipped in a hot bath of molten potassium salt, it heats up and expands. Both sodium and potassium are in the same column on the periodic table of elements, which means they behave similarly. The heat from the bath increases the migration of the sodium ions out of the glass, and the similar potassium ions easily float in and take their place. But because potassium ions are larger than sodium, they get packed into the space more tightly. (Imagine taking a garage full of Fiat 500s and replacing most of them with Chevy Suburbans.) As the glass cools, they get squeezed together in this now-cramped space, and a layer of compressive stress on the surface of the glass is formed. (Corning ensures an even ion exchange by regulating factors like heat and time.) Compared with thermally strengthened glass, the "stuffing" or "crowding" effect in chemically strengthened glass results in higher surface compression (making it up to four times as strong), and it can be done to glass of any thickness or shape.

I did glass research in college so I'm a sucker for this sort of thing. (via @joeljohnson)

Interesting explanation of Prince Rupert's Drops withFeb 19 2008

Interesting explanation of Prince Rupert's Drops with accompanying video demonstration.

The very high stress within the drop gives rise to unusual qualities, such as the ability to withstand a blow from a hammer on the bulbous end without breaking, while the drops will disintegrate explosively if the tail end is even slightly damaged. When this happens, the large amount of potential energy stored in the drop's crystalline structure is released, causing fractures to propagate through the material at very high speed.

I did research on glass back in college but I never heard anything about this.

Italian scientists have created glass made outJun 19 2006

Italian scientists have created glass made out of carbon dioxide. At high pressure, instead of forming a crystal (dry ice), the CO2 forms a clear, hard, vitreous material. More info. (Little known fact: I did research on glass in college, rubidium and cesium borosilicates mostly. Here's a few citations on Google Scholar.)

Tags related to glass:
science physics

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