The majority of the glass you see in commercial and residential spaces (think windows, doors, shower enclosures, microwaves, etc.) has been tempered. This is because tempered glass is extremely strong. Approximately 4 times stronger than “regular” glass, tempered glass will never just crack. In the event that it does encounter a blow big enough to shatter it, tempered glass shatters into small granules instead of sharp shards. This safety precaution is another reason tempered glass is so widely used.
So what makes tempered glass so much stronger than annealed glass? The answer lies within the production process. Here is how tempered glass is commonly made:
First, the glass is cut to the desired size. To ensure the integrity of the glass, cutting must take place before the tempering process begins. To reduce the chance of breakage during the tempering process, the glass is examined for any imperfections. Sharp edges are removed with an abrasive, like sandpaper. Then the glass is washed.
After the glass is prepped, it is sent through a tempering oven that heats the glass to a temperature of over 1,112 degrees Fahrenheit. (That’s as hot as lava!)
Next, the glass is cooled in a matter of seconds via a high-pressure cooling procedure called “quenching”. As the glass is blasted with high-pressure air, the outer surface cools far more quickly than the center. When the center cools, it tries to pull back from the outer surface. This keeps the center in tension while the outer surface goes into compression. This is how tempered glass gets its strength – glass in tension is about 5 times more breakable than glass in compression.
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