Archive for January, 2005

Glass

January 19th, 2005 by dstmartin
 

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Glass. It’s all around us, and we look right through it. We’re going to change that, today on Engineering Works!

No matter where you are, right now, chances are you can reach out and touch glass. It’s everywhere — your car window, the screen on your computer monitor, that glass of orange juice on your kitchen table. But what is this stuff?

Glass has been around since the beginning of time. It’s basic ingredient is a substance called silica. You probably know it better as sand. Heat sand until it melts — about three-thousand degrees Fahrenheit — and you get glass.

The oldest glass we know of is obsidian, the dark glass left after volcanoes erupt. Ancient people used razor-sharp chunks of obsidian like knives. Humans have been making glass and using it for almost 6,000 years. Ancient Egyptians molded pots out of glass and the Persians knew how to blow it into hollow containers. We’ve had flat glass in our windows since the Romans.

These days, materials engineers adjust the properties of glass to be almost anything they want it to be – crystal clear for expensive tableware, tough and elastic for automobile windows, heat resistant for the tiles that protect the space shuttle from the fiery heat of re-entry. In fact, pure silica glass like we talked about earlier is too expensive for most uses. So we add stuff that lets it melt at cooler — and cheaper — temperatures.

Our glass is full now. See you next time.

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