I've read that the newer Pyrex glass kitchenware shatters easier than it used to and throws glass quite a ways, and today it happened to me.  Probably partially my fault, but I'm not going to use Pyrex to heat things or cool things ever again.

Instead of using a metal frypan, I sometimes use a large Pyrex bowl in the microwave to cook things that get very hot, so I don't ruin my plastic microwave safe bowls.  

Like I had in the past, today I put some butter in the bowl and started to brown it in the microwave oven.  After it's brown, I put some veggies in and cook them.  

My microwave oven doesn't have a rotating bottom that distributes the microwaves evenly, so as to cook the food evenly.  Instead, It uses a stirrer where the waves come in at the top of the oven.  It used a belt from a motor to drive the stirrer, but It broke years ago.  I've tried several belts since the old one broke, but none of them work more than a couple of days, so until I find a belt that works, I've just been rotating the food manually several times during cooking to get a more evenly cooked meal.

However, today I was busy doing something and forgot to rotate.  After a few minutes, I smelled a slight burnt odor, and I found some food residue that I'd left in the bowl had burnt, probably where the microwaves were concentrated.  There was also what looked like a melted spot of the Pyrex glass at that place.  Hard to believe, but that's what it looked like.

The butter still wasn't brown, so I rotated the bowl and planned on checking that melted spot later.  Just a few seconds after I closed the door and hit the power button, I heard a shattering explosion inside the microwave oven.  Opening the door, I found at least a hundred pieces of Pyrex glass, some very small and sharp.  While cleaning up the glass, I found a piece that indeed looked like it had melted.

It took half an hour to clean up, but I sure was glad it didn't happen while the door was open, or after I had picked it up.  It might have cut me, and certainly would have thrown glass all over the kitchen.  Whew!  Lucky me!  

Since Corning sold the rights to produce Pyrex cookware in the USA to World Kitchen, LLC in 1998, it's been made with soda lime glass instead of borosilicate glass like it used to.  Corning still sells borosilicate Pyrex outside the USA, but this soda lime glass is cheaper to make, and it appears to shatter easier as well.  World Kitchens denies it shatters easier, but Consumer Reports magazine ran tests and said it does.

In any case, from now on, I'm not going to use any kind of glassware in any kind of oven, or even the freezer.  Probably not in the refrigerator either.

Snopes article:   http://www.snopes.com/food/warnings/pyrex.asp

Wikipedia article:   https://en.wikipedia.org/wiki/Pyrex

Views: 87

Replies to This Discussion

Thanks, and I'm glad you're not hurt! 

Glad you weren't hurt, Spud.  What a mess to clean up.  Buttery shards of glass.  

Several years ago I broiled a filet mignon in a small Pyrex dish about 5" x 8".  While it was in the oven I heard a loud pop.  Turns out the dish cracked in half into two pieces.  I guess the heat was too much for the dish to be on the top rack of the oven, under the heat of the broiler.  I'm glad it didn't shatter.  Luckily the filet was unscathed.  I should have used a metal pan.

This was a Pyrex dish from the 1970's or so.  Perhaps no glass product should be used for broiling, and I was just ignorantly unaware.  

Thanks Lilac, Plinius, & Carl.  

Buttery shards of glass indeed, but I would have been very bummed if I'd had to clean them up from the kitchen floor, on top of and behind all my kitchen appliances & food storage containers, in the sinks, the counters, the table, and out of my padded chair.

I was careful cleaning the microwave, but still got pricked a few times.

Spud, thanks for describing your event.  I'm really glad you weren't injured!

I have known for some time about the new, sodium glass Pyrex having a reputation for exploding.  The main issue that I remember, is if you sit a hot casserole dish on a wet, cold stone counter-top.  The sudden temperature change is the issue there.

I imagine your microwave situation is similar.  Maybe some superheated oil got into a scratch in the bowl and blew it up.

Since I'm cheap, I get my Pyrex at estate sales and Goodwill.  It's all quite old, so is probably Borosilicate glass, the better stuff.    I do try to make sure there are no scratches or cracks.

I like pyrex because of its baking qualities.  It cooks evenly, has good heat conduction, and I can see through it to judge whether things are done.  For breads or pies, I look for browning.  For casseroles, I look to see if it's boiling. 

Even though I've heard about the exploding dishes, I will continue using it.  Aluminum reflects heat and changes the cooking.  Steel rusts.  Nonstick is just crummy stuff and probably makes toxic fumes.  I don't care for stoneware, which also changes the cooking properties.  I do like cooking things in cast iron, whenever I can.  Some breads are great, baked in a cast iron skillet.    But I don't have cast iron bread loaf pans yet.  I don't use glass in the broiler or on the stovetop, and I always set it onto several thick folded dry terry cloth towels, or more often, a wooden board, or on a board made with cork wine bottle stoppers. 

I don't understand the physics, but it looks like Pyrex glass softens at 820 C, which would be 1508 degrees F.  Wow!  Is that possible in a microwave?    Maybe there was some other material on the glass that melted?  I don't know.   Soda lime glass softens at 707 C, which would be 1305 F.  I've done that using a Bunson burner, many years ago.

When I was a grad student in microbiology, we had to boil nutrient agar in round bottom flasks, then wire them shut and put them in an autoclave to be sterilized.  Autoclave heats under high pressure.  Once, something happened - maybe a scratch in the glass, or I knocked it against the edge, I don't know - and the flask that i was removing from the autoclave exploded.  That resulted in superheated agar burning my  face, arms, and scalp, and shards of glass sticking out of my face.  I don't remember, but I imagine I was wearing safety glasses, even though they were really reckless with safety in those days.  There was another grad student who was given the name of "Boom Boom Smith" after he exploded a hydrogen-filled plastic glove box and blew himself  into the lab next door, but survived. 

Actually, I think some of my casserole dishes are mostly not Pyrex, but some other Corelle ceramic product.  That's the covered ones, and those have Pyrex glass lids.

Just be careful!  No more exploding pyrex please!

Daniel, your science lab story reminds me of an episode I had in college, though it's not about explosions.  As a music major, I was required to take a "Physics of Music" class.  At the time, my lab partner and I were alone in the classroom doing tensile tests on springs.  For one measurement we needed to stretch the spring a fairly long distance, so we hooked one end on the handle of the window latch and started walking and stretching in the opposite direction.  I can't remember who was holding the other end, but it slipped out of our hands and sprung back toward the window, breaking the glass and flying to the ground outside two floors below.  As you can imagine, we did a lot of laughing. 

Daniel, your autoclave accident sounds bad.  I don't think I would have had that bad a result if my bowl had exploded in my hand.

On a side note, I looked-up nutrient agar to see what it was, and found something interesting.  The Wikipedia article said it's cooled to ~122°F before putting the lid on.  That agrees with what one guy said that was talking about Sous-Vide cooking, (which I've been doing some of).  He said 122°F will kill all pathogens if held at that temperature long enough.  

What do you say?

"Wow!  Is that possible in a microwave?"  That's what I wondered, and still do.  I Googled the subject and have read some interesting posts.  So far, it sounds like it may be possible.  Here's some of the posts:



One thing about my accident that I found interesting, was that for about a minute or two after the explosion, while I was cleaning, I kept hearing cracking noises from some of the pieces.  

Also, I saved the piece that looked like it melted, and when I examined it a couple of times over the next 24 hours, I found that two small pieces had broken off of it.




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