How to Build Tempered Glass
Tempered glass uses controlled heat treatments to make it stronger compared with normal glass. Ordinary glass breaks at about 6,000 pounds per square inch (psi), while tempered glass can withstand approximately 6,000 psi. Tempered glass is also more brittle and breaks into small, dull pieces, making it safer than regular glass. Tempered glass has a variety of common applications such as car windows, glass furniture and cookware.
Things You'll Need
- 1,200 tons molten glass
- 200 cubic meters molten tin
- 9 m x 45 m glass furnace
Instructions
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1
Make the molten glass. The precise composition varies by application, but glass typically contains 63 percent silica sand, 22 percent soda and 15 percent limestone. Mix the ingredients thoroughly and heat them to a temperature of about 1,200 degrees Celsius.
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2
Use the float process to make sheets of ordinary glass. The molten glass is poured onto a bed of molten tin. Reduce the temperature of the glass gradually from 1,100 degrees Celsius to approximately 600 degrees Celsius. Lift the glass out the tin bath, and allow it to cool completely.
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3
Cut the glass and drill any needed holes before tempering it. Glass can't be cut by ordinary means once it's tempered.
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4
Heat the glass in a kiln to at least 650 degrees Celsius and remove it from the kiln. Subject the glass immediately to blasts of cool air from fixed or rotating nozzles to cool the glass down to a temperature of 200 to 300 degrees Celsius.
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Examine the effect of rapid cooling on the glass. Cooling the surface of the glass more quickly than the center creates an initial compression on the edges and surface of the glass. This initial stress must be overcome by any subsequent stress before the glass will break.
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