Why Pyrex Bowls "Explode"


A reader wrote in because he set his Pyrex bowl on the stove top to reduce some broth, and the bowl promptly “exploded.” It appears, through googling (and You Tubing), that a great many people do not realize that Pyrex bowls have a tendency to shatter violently and dramatically when placed on a stove top or otherwise heated/cooled rapidly. And, of course, this probably has to do with the fact that Pyrex isn’t going to advertise “may shatter” as a feature of their product. In fact, there’s no mention of “shattering Pyrex” on their website at all. Yet, shatter it does. Why?

Why Pyrex Shatters:

Pyrex is made of glass. When glass changes temperature rapidly it can undergo “thermal shock.”

The text book definition of thermal shock is: “Stress produced in a body or in a material as a result of undergoing a sudden change in temperature.”

When a Pyrex bowl is heated or cooled rapidly, different parts of the bowl expand or contract by different amounts, causing stress. If the stress is too extreme, the bowl’s structure will fail, causing a spectacular shattering effect.

The main way to avoid this effect is to be mindful of how quickly you change the temperature of Pyrex. Stove tops and broilers conduct heat quickly, and will likely cause the bowls to fail. Taking a bowl directly from the freezer and putting it into a hot oven might also trigger breakage.

Are Pyrex Bowls Dangerous?

Maybe. Pyrex bowls were originally made of something called borosilicate glass, which is very resistant to thermal shock. Currently, Pyrex is made of soda-lime glass, presumably as a cost-cutting measure, as soda-lime glass is very inexpensive. Also, Pyrex is no longer made by the original manufacturer, and is essentially a brand name, rather than a material.

What Now?

The Pyrex website makes no mention of a change in materials, and does not specify what type of glass is used in their products. They claim: “PYREX

glassware products can go directly from refrigerator or freezer to a microwave, convection, or preheated conventional oven.”

Since Pyrex is no longer made of the same special thermal shock resistant glass, one should take extra care when using it. Do not place Pyrex on your stove top. Do not change its temperature rapidly, regardless of what the website says. Pyrex, in its current incarnation, should be treated more like any other piece of glass. —MEGHANN MARCO

Features And Benefits Of Pyrex [Pyrex]
Soda-lime Glass [Wikipedia]
Borosilicate Glass [Wikipedia]
Thermal Shock [Wikipedia]
Definition of Thermal Shock [Answers]

Comments

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  1. What a dork.

  2. Dilbitz says:

    OMG. What’s up with that video? What a strange man.

  3. lawnmowerdeth says:

    Thanks for the heads up. We got a Pyrex set as a wedding gift, and I always assumed it was as good as it was years ago.

  4. Rachel says:

    My sixth grade science teacher exploded a Pyrex test tube.

    The teacher just smiled and wouldn’t answer me why it exploded. So much for learning.

  5. haba says:

    I wish I had never hit play. That man was very, very annoying.

  6. wotan says:

    I was making jello shots a few years ago and poured some boiling water into the pyrex container which held the jello mix. It was fine and then I took a spoon to stir it and red, gooey, sticky, sugary, nasty liquid, and glass shards exploded EVERYWHERE. I picked a few pieces out of my fore-arm and a few pieces out of the drywall. I spent 2 hours cleaning up jello sludge from the undersides of my kitchen cabinets, walls, refrigerator, and other places (furthest away was 15 feet).

    Later during the party someone actually found a glass shard in their jello shot. That would have definetly been an unwanted side effect had they consumed it. Booooo!

  7. Mike_ says:

    I had a (room-temperature) Pyrex baking dish shatter when I put it in a 350° oven. Lasagna and broken glass everywhere. Ruined dinner. Ruined evening. It was awful.

    Pyrex used to be one of those “trusted brands”. Now it’s total crap. Probably because Corning can’t afford to make Pyrex at the Wal-Mart price, so they compromise on quality to keep their product on Wal-Mart’s shelves.

    Don’t buy Pyrex. If you have any newer Pyrex stuff, I strongly suggest you get rid of it. If it’s manufactured to the same standards as my baking dish, you’ve got a disaster waiting to happen.

  8. Greganda says:

    I heated something in a Pyrex bowl in my microwave. It shattered so explosively I thought a bomb went off in my kitchen.

  9. timmus says:

    Pyrex bowls were originally made of something called borosilicate glass, which is very resistant to thermal shock. Currently, Pyrex is made of soda-lime glass, presumably as a cost-cutting measure, as soda-lime glass is very inexpensive.

    That really pisses me off. I had equated our Pyrexware with the rugged Pyrex I used to use in chemistry labs in the 1970s. Lately I’ve even been putting stuff on the stove from time to time. Corning and World Kitchen are a bunch of cheapass bastards in my book now.

  10. timmus says:

    That WordPress (?) problem is back… my post I just made has not appeared. I’m guessing this post will cause it to appear now.

  11. TechnoDestructo says:

    I exploded a pyrex bowl on a stovetop as a child in the mid-80s.

    When did they make the change?

  12. KevinQ says:

    I had a glass lid to a slow-cooker sitting on top of my stove once, and I turned on the wrong burner to heat some water, and walked away. (Two mistakes, I know.)

    About a minute later, I heard the sound of a bomb exploding from the kitchen. It was the glass lid, and it threw glass everywhere. Thankfully, nobody was in there or got hurt.

    Beware of glass in the kitchen.

    K

  13. acambras says:

    I started cooking when I was a little kid, so I learned the hard way about putting Pyrex on the stovetop — fortunately, I wasn’t hurt and I don’t think my mom never seemed to miss her Pyrex measuring cup.

    But the other night I was cooking and checked the bottom of a bowl to make sure it was Pyrex (and therefore ovensafe). I do remember seeing a warning not to put it on the stovetop.

  14. winnabago says:

    Regardless of what it is made of, any glass that is heat tempered has the ability to explode violently. Such as your side windows in your car. This is actually a safety measure, to keep shards from forming in an accident. It is also stronger to impacts and , up to that point of breakage. I don’t know if pyrex is tempered, but it sounds like it would be if it explodes like that under temperature changes. This happened to me once as I poured cold water in a hot baking dish. Lesson learned.

    Note that your windshield is not made like this, because any rock that takes a chip out would cause the whole piece to fail. It is instead laminated with plastic film to hold it in place.

  15. homerjay says:

    My sister took a pyrex dish out of the oven and put it on the stovetop. Within minutes there was glass EVERYWHERE. Crap Crap Crap!

  16. Harlan says:

    Is there anyone else who sells real borosilicate kitchen wares? Competitors to Pyrex?

  17. chickymama says:

    I suprise no one has heard of this before. I saw a newspiece several years ago when someone rec’d 2nd degree burns because they heated water in a glass bowl and proceed to stir it with a metal fork. A scientist came on and explained the process. It wasn’t a pyrex brand either. I love pyrex bowls and cookware. Never has a problem. To me this isn’t news.

  18. chickymama says:

    sorry about the bad grammer on my above comment.

  19. phrygian says:

    I exploded an old (70s/80s) pyrex casserole dish a few years back by using it on the stovetop. I learned my lesson — and noted that my new Pyrex pieces all had warnings not to use them on the stovetop. (The old pyrex dish didn’t have any warnings on it.) Now, I only use my pyrex for measuring, storing and microwaving.

  20. No glass is immune to shattering from sudden temperature changes, and glassware in general can be expected to become more fragile as it ages.

    But borosilicate glass is, indeed, much tougher than plain soda-lime glass. Corning’s decision to throw their good reputation down the toilet here is like Dupont deciding that from now on “Teflon” will just be, what the heck, black paint or something.

  21. B says:

    Harlan:
    According to Wikipedia, Bodum makes borosilicate glass kitchenwares. Mostly teapots, french-press coffee makers and the like.
    http://www.bodumusa.com/shop/home.asp?CHK=1288

  22. MeOhMy says:

    PYREX® glassware products can go directly from refrigerator or freezer to a microwave, convection, or preheated conventional oven

    Says nothing about putting it on the stovetop. Come on folks, this is basic knowledge.

    Maybe less basic knowledge, but don’t pour boiling water in to a cold glass container. And don’t take a piece out of the oven using a wet towel as a potholder. Use a real oven mitt. These tips apply to glass, stoneware, earthenware, clay, even cast iron. Plunge a hot iron skillet into cold water, it could crack.

    Now you folks that just put a piece in the oven and had it blow, you’ve got something to complain about. That shouldn’t happen.

    And it is pretty weak that they switched to cheaper, crappier glass!

  23. SuperJdynamite says:

    “I don’t know if pyrex is tempered, but it sounds like it would be if it explodes like that under temperature changes.”

    Since tempered glass is created by heating glass and cooling it quickly, I would think that repeated heatings and coolings would ruin the temper in a process similar to annealing.

  24. guroth says:

    Pyrex says it is safe to move from the freezer to the oven because it is. It takes time for the glass to heat up so it is not a sudden temp change. When the dish goes from hot to suddenly cold is when they begin to shatter.
    The hotter the dish gets the faster the temperature is going to drop as soon as it is removed from the heat source.

    Pyrex dishes even say not to use on the stove top and not to use them for broiling.

  25. And0 says:

    Like Troy said, Pyrex has *never* been able to go on the stovetop. I have a Pyrex baking dish from the 70s that has “not for use on stovetop or open flame” stamped on the bottom. Pyrex works well, but seriously, I thought it was common knowledge not to use it on a burner.

  26. kerry says:

    I, too, have exploded Pyrex in the past, but it was because of my own stupidity. I took a 450° casserole pan out of the oven and put it in a stainless steel sink. Boom.
    You shouldn’t ever put glass cookware over an open flame, nor should you rapidly change the temperature, regardless of what the glass is made out of.
    I’ll say this, though: I’m ticked they cheapened up the glass. I need to look at my pie pan and casserole dishes and see what they’re made out of now. (If I can, is it printed on there anywhere?)

  27. valkin says:

    Chickymama, I believe that story is about “superheating” water in a microwave.

    That happens is that the water heats faster than the vapor bubbles can form. As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point. What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid.

  28. Soulgenesis says:

    i was watching mythbusters yesterday and they were doing this exact thing with tap and distilled water.

    it seems tap water boils (at boiling point, of course) due to impurities in the water. distilled water is free of impurities, so it doesn’t boil in a microwave. upon breaking the water’s surface with anything caused a violent explosion of the distilled water.

    and i’m guessing along with the container it’s in. ;)

  29. DeeJayQueue says:

    Tempered glass ‘splodes in tiny tiny fragments and usually pretty violently, due to it being under internal tension.

    It should be pretty much a no-brainer that heating pyrex (or anything not made of metal) on a stovetop will cause it to explode or burst into flames. Cookware manufacturers spend gobs of cash every year making new and better alloys that heat up evenly along the sides and bottom of a pan, but mostly they just find out that the further something is from the flame (the walls of a glass bowl) the slower it will heat up, while things that are in direct contact (the bottom) will heat up surprisingly well.

    Putting glass dishes in the oven or the freezer is a different story because instead of directly heating just 1 part of the dish, you’re changing the temperature of the whole thing at once. If it explodes under those circumstances, there may have been a defect in the product outside its general manufacture.

    I AM rather annoyed that Pyrex changed the formula for their glass though, that’s a poop move.

  30. infinitysnake says:

    “The Pyrex website makes no mention of a change in materials, and does not specify what type of glass is used in their products. “

    That explains a lot, really- it did seem to me their product suddenly got flimsier.

    Iirc, the guy who built the hubble mirrors melted down his wife’s pyrex…can’t imagine what they’d use now.

  31. craigpress says:

    Yeah, I was baking bread and had a pyrex bowl in the oven to add water too. I usually add the water before the oven heats, but forgot to and decided to add it when the oven was at about 550 degrees. Needless to say the darn thing exploded all over the oven. Note to self: don’t add cold water to a 500 degree glass container. As a science grad student I should know this. Luckily, no one was hurt but my ego. Still had some tasty bread to eat though.

  32. krexroad says:

    I have a set of Pyrex sauce pans that are meant for the stovetop!! I use them alot to hardboil eggs, make pasta, etc. They haven’t blown up yet, but I will likely feel suspicious of them from now on. And one of my favorite things is to take them off the stove and dunk them in water in the sink! I love that sizzle sound!

  33. babette says:

    The Pyrex that was borosilicate glass was more resistant to thermal shock because the glass was made with letharge which is a by-product of a lead oxidation reaction. Thus the switch to the soda-lime glass.

  34. adamondi says:

    Everyone should take a tip from the restaurant industry as far as cookware goes. Skip the crap they sell at Wal-Mart and Target. Find a restaurant supply store or “Cash & Carry” place around you. They will be in any city or town of a reasonable size. Buy your cookware there. It will be cheaper than comparable stuff at Wal-Mart, Target, or Bed, Bath and Beyond. It won’t be as pretty as the stuff sold elsewhere, but you can beat the mother lovin’ heck out of the stuff and it will perform admirably. It is meant to endure a restaurant kitchen after all. Lots of aluminum and stainless steel, not much glass.

  35. pockyraider says:

    I had a room mate that used a pyrex container on the stove to make instant mashed potatoes. The water boiled well, but as soon as she added the milk, she turned away to get the bag of potatoes. Good thing she did; it exploded everywhere, leaving glass embedded into the walls, not to mention unattractive burn marks into the kitchen floor.

    Thankfully, the apartment check list noted none of this when we had our walkthrough before move out.

  36. 5cents says:

    As someone mentioned above, dont put glass on a stove top. Pyrex used to emboss a warning on their wares saying “Not safe for stove top.” If don’t anymore that sucks. However people seem to be getting dumber every day trying the whole straight out of the freezer ontot he stovetop thing. That is certainly common sense and something your mama should have taught you. To what extent is the manufacturer responsible for one’s stupidity? Finally, all glass products that contain hot items will eventually fail due to cyclical thermal stresses and fractures.
    5cents
    Current courses: Thermal effects on composite materials
    MASc Aerospace Engineering.

  37. I’m still in awe that someone would put a glass bowl onto a flame or heating element. That takes special, deep reserves of dumb.

    Perhaps these folks are confused by the fact that Pyrex makes or used to make chemistry lab equipment. Do you cook in lab equipment? Do you use a stove in a chemistry lab?

    All of my Pyrex brand products are either silkscreened or embossed “Not for Lab or Stevetop Use”.

  38. Legodude522 says:

    So… Robin Williams still is doing comedy. Good for him.

  39. Actually, my Pyrex products all bear the mark “Not for Lab or Stovetop Use.

    Not sure what a Stevetop is. Maybe something used at MacWorld.

  40. Keter says:

    Remember Corningware’s Visions clear glass cookware? I loved those, used them for years with never a problem. I moved and got a new flat glass cooktop, and it said don’t use Visions on it, but didn’t say why. I’m now using cast iron instead, but wonder if anyone knows why you can’t use visions on a glass cooktop.

    Yo, Lib Cajun…’stevetop’ is Chinglish for ‘stovetop’, didn’t you know that? ;o)

  41. synergy says:

    I guess that’s obvious to me, but then I work with real Pyrex at work in a lab and can tell the difference between it and glass.

  42. Kat says:

    Yep yep, friend of mine had one on her stove and sat down at the kitchen table – if she hadn’t been reading a book (and holding it in front of her face), the shards would have hit her face when it exploded.

  43. I’m now using cast iron instead, but wonder if anyone knows why you can’t use visions on a glass cooktop.

    I’m guessing it’s because the insulating layer of air between the two is almost nonexistent, leading to a too-rapid heat transfer to the Visions cookware.

    Visions works on other stovetops because the heat is transferred through convection (indirect) heating or low-area conduction. Conduction over the entire surface of the cookware might not allow it to expand at the right rate to be used safely.

    Just a theory.

  44. suckonthat says:

    Do you use a stove in a chemistry lab?

    Uh, actually I do. But it’s called a Bunsen burner.

    For the other people who use Pyrex in an actual lab setting (cause there seem to be a few posting here): that glass is the original borosilicate kind right? I put some pretty noxious stuff in those suckers and I’d really like to avoid being sprayed with glass and carcinogens the next time I put one in the microwave or on a hot plate.

    Though now that I think about it, they must be of better material than the cookware Pyrex because they can survive an autoclave…

  45. BaseballHeavy says:

    The original white Corningware (square containers) is safe to use on the stovetop. The newer Corningware (round and oval with ribbed exterior, aka French White) is total crap. I used to work for World Kitchen, who took over Corningware products after Corning sold their retail division to concentrate on fiber optics and such. Most of it is junk. Let’s hope they never change the Corelle dinnerware.

  46. silverlining says:

    Folks have spent a lot of time rightfully excoriating others who have burst pyrex on the stove top. Seems the guy in the video (no matter how annoying) used the glassware as Pyrex itself describes how it should be used.

    If folks use the glassware as the company prescribed and it still blows up, seems like the company should be held liable.

    Babette–are you saying that there was a chance of lead contamination from the original glass, thus the decision to switch?

  47. So, I was the one who originally sent in this story, and for the record, I do feel like it wasn’t a great idea. A couple of sidenotes responding to other people’s comments:

    1) I poured already boiling broth into the 13×9 glass dish. The dish was at room temperature and it was on the stovetop, but on burners that were turned off. I turned the stove on to LOW after letting the glass warm up from the broth. As the heating element warmed up, I was stirring the broth so as to make sure the glass warmed evenly. It exploded after approx. 20 minutes simmering. I just wanted to allay any ideas that I put it from the freezer onto the stove or something.

    2) Interesting to me as I researched “exploding” pyrex cookware is that so far every example that showed up in a google search happened to someone with a 9x13inch baking dish. Also, every person noted that the dish was at least a year old (mine was between 1 and 2 years). These similarities between my experience and that of others led me to the following Link. I’m interested if people with different dish sizes/shapes have experienced the same problem or if it is more common for some dishes as opposed to others… Also of note is that there certainly seems to be an increased risk of explosive failure as the Pyrex ages. I think that this is a message that should be better communicated, though I want to note that I can blame no one but myself for contradicting the manufacturer’s stated warning, no matter how careful I attempted to be.

    With all of the complaints of exploding dishes even for those who follow the directions, I’m going to be particularly careful not to keep around old glass bakeware. Also, I’m going to be investigating whether or not anyone makes “actual” Borosilicate Glass cookware and trade in (throw away) my current Pyrex stuff.

    Raul
    PS: thanks to most of you for not ripping on me too bad for disregarding the manufacturer’s warnings. It’s getting hard to know which are just legal ass-covering (Warning: McDonald’s coffee is hot, it might burn you if you pour it on your crotch, dumbass…) and which are legitimate.

  48. Tuffy says:

    Pot roast. Christmas dinner. Making gravy from drippings on the stove top. BOOM.

  49. Her Grace says:

    I had a bodum french press (small coffee maker, oui?), made out of the good stuff. It mysteriously lost a wedge of the top edge in the dishwasher one day, after about 7 years of constant use. No previous cracking, no mishandling, I put it in normal and it came out missing a 2″ long section of the rim. It was very weird. We never found the missing bit, either. So that’s my experience with borosilicate.

  50. MeOhMy says:

    I poured already boiling broth into the 13×9 glass dish. The dish was at room temperature and it was on the stovetop, but on burners that were turned off. I turned the stove on to LOW after letting the glass warm up from the broth. As the heating element warmed up, I was stirring the broth so as to make sure the glass warmed evenly. It exploded after approx. 20 minutes simmering. I just wanted to allay any ideas that I put it from the freezer onto the stove or something.

    The bolded parts are why it exploded. You were fortunate that it did not explode when you were pouring boiling liquid into the room temperature container.

    You can’t put them on a stovetop burner. Ever. The burner gets extremely hot. Stirring won’t help it heat evenly enough because there is so much concentrated heat coming from the burner that one part is getting really really hot no matter how much you stir the contents.

    The 14×9 could well be more susceptible to breakage because of it’s shape – the large flat bottom surface.

    Nonetheless remember this simple formula: Pyrex + Burner = Explosion

    It doesn’t matter what size or shape, how high the burner is turned up or how much is in it.

  51. elemental77 says:

    You can read my own account of an exploding Pyrex dish – one which doesn’t seem to conform to the “obvious” reasons I keep seeing mentioned (aside from Pyrex no longer being made of the same great stuff) – here:

    http://quietest.blogspot.com/2007/03/exploding-pyrex.html

    If you have input as to why this happened, I’d like to hear it. I’d like it better if it was friendly input. :)

  52. Catherine Sarah Te Whare says:

    Don’t use Pyrex, I have had two dishes explode on me they are hazzardess. How Pyrex can get away with this I don’t know. I had followed all the guidelines but still it happened. I now use stoneware for all of my cooking and baking. It cost less, looks better and cleans up easily withough scrubbing unlike Pyrex.