Pyrex and Broiling
December 8, 2004 2:42 PM   Subscribe

Why are Pyrex dishes so unsafe to use under the broiler? [mi]

My friend’s husband flipped a steak halfway through cooking under the broiler last night, and the bottom of the Pyrex dish completely fell out of the piece. I thought I’d remembered that the test tubes and beakers I’d used during chemistry class were made of Pyrex, and we held those puppies up to Bunsen Burners. What’s the difference here?
posted by ChrisTN to Home & Garden (15 answers total)
 
In the broiler, the part of the plate closest to the flame (or heating element) is much hotter than the part furthest away. This change in temperature (or gradient) over the plate results in high stresses within the plate that make it unstable.

It can take high temperatures, but only if applied evenly. That's also why they say not to rinse a hot plate under cold water... it results in a temperature gradient.
posted by Doohickie at 2:53 PM on December 8, 2004


Holy frijoles, the exact - and I do mean exact, cooking steak under the broiler - same thing happened to my SO and I. But the resulting semi-shattered pyrex shards were pretty damn cool.

All I can remember is that when we told people about this, everyone replied that it was common knowledge that you couldn't use pyrex in a broiler or on a stovetop.
posted by googly at 2:57 PM on December 8, 2004


in general things expand when you heat them. so if you heat one area, rather than another, of an item made from a brittle material then it's likely to crack because the different areas no longer "fit together". for ductile materials like metal this isn't a problem - the metal just "gives" - but for very hard/rigid materials like glass and (some) ceramics, they can easily crack.

pyrex is kind of strange. the inside is actually "too small" for the outside, so it's constantly "pulling itself together". this is a result of the manufacturing process (called heat tempering, giving surface compression). it's also made from a glass that expands less than normal with temperature (borosilicate). so when it's heated the problem (1) isn't so bad because it expands less and (2) provided the stresses are less than the internal stress due to the "shrunk" core, the thing holds itself together (it's a bit more complicated than that: things break because of surface scratches; the surface compression stops scratches from growing).

however, it's not perfect. putting it close to a radiant heat source (i guess a broiler is american for a "grill"?) is going to heat up the parts near the flame/element much much more than the rest. you just pushed it too far.
posted by andrew cooke at 3:30 PM on December 8, 2004


A broiler's a grill, only upside down. Typically, broiling is done in an oven with it set to a "broil" setting, with heat coming from the top element.
posted by zsazsa at 3:49 PM on December 8, 2004


Also! Please DO NOT give in to your insane impulse to dump a cup of cool water into the bottom of a pyrex pan that has been roasting a large hunk of meat for an hour or so, as the pan will explode instantly in a dramatic noisy fashion and spray broken glass and hot grease all over the bottom of your oven and be amusing only in retrospect. Ha ha ha!

Um, yeah. That's what a "friend" told me...
posted by naomi at 4:39 PM on December 8, 2004


"All I can remember is that when we told people about this, everyone replied that it was common knowledge that you couldn't use pyrex in a broiler or on a stovetop."

This information is actually pressed into every piece of Pyrex bakeware I've ever owned. Something along the lines of "Safe for freezer, microwave & oven; Not for broiler or stovetop use."
posted by bcwinters at 5:13 PM on December 8, 2004


Most broilers I've ever seen are made with a pan built in so you can cook stuff on them directly, though with something like a steak, it's a bit more of a hassle to take it out and wash it up. One reason I'm a fan of the outdoor grills here at our place. Might not be practical in Tennessee in December, though. 72 F and Sunny in Dallas tomorrow - bad for the "holiday spirit", good for outdoor grilling!
posted by sixdifferentways at 5:43 PM on December 8, 2004


Naomi: The Grill + h2o + Pyrex pan formula can also be great for a laugh! Ha! Works especially nicely at parties.

bcwinters: I am now leaving for my kitchen to investigate. By gum!
posted by mimi at 6:05 PM on December 8, 2004


I had a "pyrex" dish explode in the oven once. It sounded like all the shelves in the refrigerator collapsing at once. Two-thirds of the baking dish was gone; the bottom of the oven was covered with the sort of little diamonds you see remaining from a car accident.

On reflection, I don't think it was an actual "Pyrex" [tm] brand dish...some similar off-brand.

It appeared that the veggies had somehow all landed in one end of the dish. One end dried out too fast, which led to a heat difference between different ends of the dish, which led to the blow-up.

I never got all the little "diamonds" out of that oven.
posted by gimonca at 6:44 PM on December 8, 2004


One reason I'm a fan of the outdoor grills here at our place. Might not be practical in Tennessee in December, though. 72 F and Sunny in Dallas tomorrow - bad for the "holiday spirit", good for outdoor grilling!

This was my friend in Minneapolis this happened to, so it would be even more unfortunate, I think, to try grilling out much!

Thanks for all the great responses...they make a lot of sense.
posted by ChrisTN at 7:25 PM on December 8, 2004


Damn, now I'm tempted to heat a pyrex dish to red-hot temps, then toss it in the snow.

I'm not going to because (a) I don't want to be forever picking glass shards out of the yard; (b) I don't want to be forever picking glass shards out of my face.

Must. Not. Perform. Experiment.
posted by five fresh fish at 7:50 PM on December 8, 2004


That's why you drop it from a first-floor window and have a webcam set up close by to broadcast for all of us to see.
posted by jmd82 at 11:20 PM on December 8, 2004


On time I had a BIG pyrex bowl on one of the burners of a four burner stove at this house I had just moved in to, and I thought I turned on another burner to heat a teapot, but I had in fact started superheating the empty bowl. Of course, I realized this 5 minutes later when I walked back into the room. I turned the heat off, and everything was ok until 5 minutes later when the bowl exploded. It was beautiful and loud. I always wondered if I could have preserved the bowl by slowly decreasing the heat instead of cutting it off completely. Until now!
posted by ejoey at 2:16 AM on December 9, 2004


I've always been impressed by the behavior of angry Pyrex.

It doesn't just crack or split into a couple pieces; it shatters into billions of tiny, needle-sharp microshards.

After reading this thread, though, it occurs to me that it's time to get rid of my chipped Pyrex bowl.
posted by ikkyu2 at 5:42 AM on December 9, 2004


My dad turned on a burner under a Pyrex roasting pan once, by accident (no, really, he's an engineer, he knows that stuff). We "discovered" the mistake when we heard a violent CRASH, and looked over to see a very neat circle of pyrex on top of a cherry-red calrod, surrounded by many large, cruel looking shards of glass.

As my brother (also an engineer) put it at the time: "Dad, even Pyrex has its limitations."
posted by lodurr at 7:30 AM on December 9, 2004


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