Tempering in Glass
Tempering, or toughening, of glass is a process in which glass is first heated above its annealing temperature (about 720°C), and then rapidly cooled by jets of cool air, thus hardening the surface of the glass and leaving the center soft for a period of time. This creates internal stresses in the glass. If the glass is broken, it will break into many small pieces instead of simply cracking, making it far safer. Another advantage is that tempered glass can be up to four times stronger than regular glass. However, tempered glass cannot be cut to shape or drilled once it has been toughened.
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Famous quotes containing the words tempering and/or glass:
“Only after much tempering is steel produced.”
—Chinese proverb.
“Thales claimed that everything was water. He also put wine into water to sterilize it. Did he really believe he was putting water into water to sterilize it? Parmenides, like most Greeks, knew that wine was not water. But while lifting a glass of wine to his lips, he denied that motion was possible. Did he really believe that the glass was not moving when he lifted it?”
—Avrum Stroll (b. 1921)