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Diane T.
February 14, 2017
My memory about Pyrex exploding isn't vague and doesn't come from some internet story. I still have a scar on my leg from a pyrex bowl shattering after my mother put simmering hot sauerkraut into a room temperature bowl. Perhaps today's Pyrex is doesn't shatter unless it's at 450 degrees, but for those of us who have vintage bowls, I'd strongly recommend a bit more caution.
mikedalena
February 14, 2017
Quartz inversion is a constant in the universe. It's the laws of physics. Glass one billion years ago is glass last week. It's likely that was very hot product. In fact, your experience reinforces my statement. A cold bowl being exposed to thermal shock, the rapid change in temperature, is exactly what causes glass to shatter. Your anecdote is valid but serves to support the immutable laws of physics.
mikedalena
December 26, 2016
Thermal shock, the condition that causes glass to break from a rapid temperature change occurs at 450 degrees Fahrenheit. At 450 the electrons in the molecules of glass (quartz) jump from their A orbits to their B orbits due to the additional energy they are exposed to. This is called quartz inversion. If this jump in orbits, either when heating up to above 450 or cooling down from above 450, occurs too rapidly/all at once the material will crack. The drop or jump in orbit literally tears the glass apart. One doesn't really need to worry about putting a Pyrex dish into a 450 oven because the rise in temperature isn't that rapid when one places a Pyrex dish on the oven's rack. However, a precipitous drop in temperature from above 450 will definitely cause the dish to crack.
Basically, don't stress about your dishes if you're cooking well below the 450 mark and only be concerned when you're above that mark if you take the cooking container from a 450+ oven. In those instances don't set the dish on a cold tile surface or directly into the freezer. Place the hot out of the 500 degree oven dish on a wood cutting board or a rack of some sort to prevent thermal shock.
I'm not afraid of glass Pyrex dishes or ceramics with chips in them due to the immutable laws of physics (love science!) but I would throw out anything that is cracked. It's structure is weakened and it is a disaster waiting to happen.
Basically, don't stress about your dishes if you're cooking well below the 450 mark and only be concerned when you're above that mark if you take the cooking container from a 450+ oven. In those instances don't set the dish on a cold tile surface or directly into the freezer. Place the hot out of the 500 degree oven dish on a wood cutting board or a rack of some sort to prevent thermal shock.
I'm not afraid of glass Pyrex dishes or ceramics with chips in them due to the immutable laws of physics (love science!) but I would throw out anything that is cracked. It's structure is weakened and it is a disaster waiting to happen.
Daisy P.
April 22, 2020
This is really good information Mike thanks! I was just stressing because I Recently bought a vintage pyrex with a chip on it. I didnt buy it just to display it. So I can use it in an oven that is below 450 degrees?
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