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I'm not an expert, and I wouldn't expect Pyrex to do it, but it looks like a heat stress thing.

Hot bowl, cold counter top. The counter top sucks the heat away from the bottom of the bowl making it contract but the rising steam/heat off the contents keep the top warm and expanded. Too big a difference and craaaack the bowl splits, probably along a fault or some other weakened area.

But that's just an, reasonably uninformed, guess.

yeah, i'd agree with SpaceDog. that happened to my sister a few years ago, when she put a Pyrex dish on a cold marble surface.

too bad about the meatballs!

where's alton brown when you need him?

my bet is just that you had a tiny defect in just the right (or wrong) place.

Spacedog is right. Glass is very brittle. The bottom of the bowl was contracting from the cold, and the top was warm from the meatballs.

The same thing can happen if you put a glass dish on the stove top - which is why those large pyrex measuring cups have "not for stove top use" stamped on them.

I just checked wikipedia, and it seems your 6 year old pyrex bowl may not be pyrex at all. Apparently in 1998 they moved from using borosilicate glass to a soda-lime glass. From what I understand borosilicate glass is more resistant to thermal stresses that soda-lime glass, so maybe we can't expect the same performance out of new pyrex.

The wikipedia article (http://en.wikipedia.org/wiki/Pyrex) links to a forum of people complaining about this exploding kitchenware (http://www.consumeraffairs.com/homeowners/pyrex.html).

At Christmas this year I went to meet my girlfirend's family for the first time. We went skiing and rented a condo near the hill. When our turn to make dinner came around I thought I'd do some nice baked pork tenderloins. I found the pyrex baking dish, and baked off my tenderloins. While they were resting I decided to make my pan sauce right in the baking dish, because it's pyrex right? The sauce reduced beautifully, and for all time I'll remember it as the greatest sauce that wasn't. The dish had no problem with exposure to the direct heat of the elements, it was about 5 minutes later when the dish began to cool that it exploded into a thousand tiny pieces, and my glorious sauce dribbled away between the burners.

This is pretty much my own fault, because I was clearly misusing the dish, but still a disappointment. Also my dish may not have been pyrex at all. Apparently pyrex is supposed to break into large pieces, whereas mine shattered into thousands.

Kevin -- very interesting. Thanks for the links. I double checked and mine was stamped Pyrex and it did break into large pieces. I wonder if mine was made from borosilicate glass to a soda-lime glass. I'll see if I can get a contact at Pyrex consumer products to help us with this.

That is just such a sad picture Chris, sad that your dinner was ruined and sadder still that the old standby broke on you.

But I agree with what everyone else has said, cold surface, hot dish, not a good combination.

It is sad. All that work and I lost my poor meatballs . . .

Even if you did have a borosilicate glass bowl, they're not indestructible, just more sturdy. I agree with the other posters that it was from placing a hot bowl on a very cold surface, especially since stone is not a good conductor so the temperature between the two (glass and stone) stays unequal for longer. Also, I'm guessing that your microwave could have created a super-heated area with something as dense as the sauce and meatballs. Were you stirring it as you reheated it?

Sorry you lost your supper.

regards,
trillium

Actually, trillium, to be geeky, stone is a good conductor comparitively. Think of how much cooler it would feel than wood even if they were at the same temperature. The stone is conducting the heat away from your hand much better than wood.

What you're talking about is heat capacity, and in that sense, you're right. Stone can suck in a lot more heat before its temperature rises. So you've got a double whammy of a (relative) heat black hole. It sucks away the heat quickly and can do it for a long time. Definitely a recipe for bowl of meatballs disaster.

As an obsessed Alton Brown fan, one of his cookbooks discusses Pyrex glassware. Apparently, heating and cooling of Pyrex weakens the structure over time. Given that your bowl is 6 years old, I'm guessing the microwaving then cooling of the bowl made the weakened bowl even more fragile.

Also, I work in a lab where we heat things in Pyrex frequently - we buy new Pyrex every year because of the fragility issue.

covered in consumerist two weeks ago

cool - your awesome commenting form won't let me include links.
click my name, it's in there now.

Oh, how sad!

Lux's comment makes me wonder if I should stop using my Pyrex bowl for double boiling. Is a metal bowl a better choice?

A few years ago, I brought 2 lasagnas in Pyrex, straight from the fridge, to a dinner party. One was meat, one was veg. It was Good Friday, so the Catholics in the house had to have the veg. I loaded them both into the oven at 450 to warm up and brown. 10 minutes later, the Pyrex with the meat lasagna violently exploded in the oven. What a mess. Heat stress, or an act of God? Luckily, the veg was big and hearty enough to feed us all.

Interesting! I have had two earth shattering pyrex experiences. One was with a bowl coming out of a microwave, carrying it across the kitchen, using an oven mit on the handle and it literally exploded. There were glass fragments and sauce everywhere. The other was when I put a luke warm bake dish into a sink of hot water. I thought it would all be okay. Again it was thousands of tiny glass fragments. Needless to say I do treat Pyrex with resect and caution.

Not a Pyrex story, but close--Corelle. When I was ten, my mom made tacos for dinner and, after the electric coil burner had cooled to what she thought was a safe temperature, she put a stack of Corelle plates on it to warm. Thankfully, we were in the dining room when it detonated--bazillions of shiny white shards everywhere.

I have never had any problems with the extensive range of both new and old pyrex that I own but my husband did have one break on him while he was still single and he cut his wrist badly on one of the broken pieces - I think its probably an age thing - the longer you've had it the more likley it is to break - just like anything really

I can actually give you a bit more of a definitive answer on this. Pyrex is indeed heat resistant, and so is often used as bakeware and also in labs as heat resistant beakers. I used a lot of them when I was a science teacher. One day we were using one of our trusty old pyrex beakers for a boiling water experiment, when it suddenly exploded on the hot plate. Luckily no students were nearby, so no-one was injured.

This can happen because though pyrex is resistant to heat, it is still a glass. Glass molecules are arranged randomly, as they are in liquids, and do not have strong bonds between them. This is why really old glass in windowpanes is thicker in the bottom- the glass has flowed down over the years due to gravity. Because of this structure, to cut glass all you must do is score it with a sharp tool and you can break it evenly, since you've lined up the molecules in straight rows and they will snap down the center. This kind of arranging effect can also happen if you smack a pyrex beaker or bowl down on a counter or hard surface. If this happens repeatedly over time, and this is coupled with the expansion and contraction of heating and cooling, you weaken the structure of the glass. This can cause it to unexpectedly shatter apart in response to a temperature change. Apparently this happens a lot at schools, since students don't tend to be terribly careful about smashing the glassware around on stuff.

The moral of the story is, treat your pyrex glassware with caution and try to avoid dealing it any sharp blows, especially against those rock hard (pun intended) granite countertops everyone has nowadays.