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Old 09-28-2015, 10:58 AM   #11
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Originally Posted by GotGarlic View Post
What if she had heated the pan and then put a hunk of frozen ground beef in it? (I'm asking out of curiosity; don't know that she did that.)
Best guess is that the ground beef isn't thermally conductive enough to cool the pan fast enough to generate the temperature differential needed to crack a pan. Put a frozen burger in a pan and most of it will remain frozen for quite a while. Liquid water, on the other hand, is a good thermal conductor and requires quite a bit of energy to go to the gaseous state (steam), and can cool the pan quite rapidly.

Think of how long it takes to heat a burger all the way through vs. how long it takes to boil off the water when deglazing a pan.
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Old 09-28-2015, 11:07 AM   #12
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Old 09-28-2015, 11:22 AM   #13
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The burger was defrosted.

Lots of interesting info here, thanks guys!
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Old 09-28-2015, 11:30 AM   #14
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CI is a brittle material as others have mentioned. It probably got a little hairline crack from banging against another CI pan or a drop. Over time the heating and cooling worked on the crack until it fractured all the way through.
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Old 09-28-2015, 12:13 PM   #15
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Brittle is a relative term. There are a variety of types of cast iron. Remember, engine blocks, cylinder heads, and crankshafts are made from CI.
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Old 09-28-2015, 12:30 PM   #16
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Perhaps there’s a metallurgist or materials engineer in the house that can shed more light on this, but failure due to thermal shock is a generally a result of rapid cooling (e.g. putting a hot pan in cold water), rather than rapid heating, especially in a household environment. Rapid cooling puts the surface of the object in tension (trying to shrink around an expanded core), and most materials are more likely to fail in tension rather than compression.

As compared to a lot of other materials, cast iron is regarded as has having good thermal shock resistance and is a fairly tough material. A lot of machine components are iron castings. There are a number of types and alloys of cast iron, and the thermal shock resistance varies among them. It’s been a few decades since I was in the metal removal industry, so I’ve forgotten a lot of details. By the way, machining metal can produce some red hot chips, and there is usually a flood of cooling water over the cutting area.

As far as the skillet breaking, I’ll guess that it was a result of previous abuse or a manufacturing defect. I can’t imagine how putting ground beef into it would cause a failure. Deglazing a pan would cause more rapid cooling than that.
I'm purposely mixing apples and oranges here. I had a chafing dish that came with two small candles, in holders, to keep food warm. The dish was made of tempered glass, not borosilicate glass. I replaced the candles, when used up with two cans of Sterno fuel to provide the heat under the chafing dish. I was preparing other parts of the meal, and had warm casserole type food (fice pilaf with chicken strips) in the chafing dish. The dish was on the dinner table and I was in the adjacent kitchen. I hear the pop of the glass shattering. There wasn't a single crack, but many chunks of glass littering my table, and impeded into the rice dish, which of course went into the trash.

I assumed that the glass was heating to quickly, and that as an insulator, the pressure built by differing rates of expansion cause the failure. I have seen glass pots, and dishes fail do to heating too quickly, especially if the heat is applied only to one surface. I would assume that the cast iron used in pans would react similarly. Though cast iron is a better conductor of heat than is glass, it is still a relatively poor heat conductor.

And yes, like you stated, rapid contraction of the metal will also cause it to fail. Most CI pans come with a warning not to throw a hot pan into cold water, so as to avoid failure of the metal.

The cause of my chafing dish failure was applying excessive heat to the dish bottom. I could see it happening with CI, though rarely.

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Old 09-28-2015, 01:19 PM   #17
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Almost anything cast can over time develop cracks and eventually fail.
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Old 09-28-2015, 01:25 PM   #18
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Fun facts:

According to

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

aluminum has approx. 4 times the thermal conductivity of CI, and CI has approx. 50 times the thermal conductivity of glass.

Borosilicate glasses have a very low thermal coefficient of expansion (don't change much in size due to temperature changes), which is what makes them resistant to thermal shock.
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Old 09-28-2015, 03:25 PM   #19
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Originally Posted by tenspeed View Post
Fun facts:

According to

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

aluminum has approx. 4 times the thermal conductivity of CI, and CI has approx. 50 times the thermal conductivity of glass.

Borosilicate glasses have a very low thermal coefficient of expansion (don't change much in size due to temperature changes), which is what makes them resistant to thermal shock.
When Pyrex started using temperd glass for their cookware instead of borosilicate glass, I was highly disappointment.

By the way, just in case your'e wondering, I agree with you and just threw in the apples to oranges comparison to highlight that the issue is with rates of expansion.

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Old 10-09-2015, 05:59 PM   #20
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Simple case of old metal being hot and cold material put into it. After thirty years of who knows how it was used this is not unusual. One of those things that makes get party chatter.
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