Have You Heard the One About . . .


Post by community member:

the Exploding Pyrex? No? Well, read on.


Some viral emails describe spontaneous ‘explosions’ of Pyrex® bakeware. The consumer advocate website, ConsumerAffairs.com, claims to have culled more than 300 ‘exploding’ Pyrex stories from Internet users around the country.

Consumer Reports conducted extensive tests with Pyrex and Anchor Hocking glass bakeware in its own testing laboratory. (Consumer Reports publishes the findings of the Consumers Union, a nonprofit organization that works to empower consumers.)

©Consumer Reports

In one test, researchers heated a sand-filled Pyrex baker in a 450°F oven. When they took the bakeware from the oven, and placed on a cool, dry surface, it ‘flew apart.’ You can view video of additional Consumer Reports tests and results at its website. Based on their tests, Consumer Reports is asking the Consumer Products Safety Commission to look into the breakage issue.

Here is some basic information regarding Pyrex bakeware:

  1. Corning began manufacturing heat-resistant borosilicate glass in the early 1900s. This glass withstood extreme changes in temperature, known as thermal shock. Railroads used the nonexpanding glass, called Nonex, to prevent the glass lanterns on rail signals from shattering.
  2. After Bessie Littleton, wife of Corning physicist Jesse Littleton, complained that her casserole dishes cracked in the oven, Mr. Littleton brought home jars made of Nonex. Using the jars, Bessie produced round, evenly-baked, golden sponge cakes. This led Corning to file a patent for borosilicate glass bakeware in 1915. Pie plates were the first borosilicate bakeware, prompting the name Pyrex.)
  3. The company began to change the composition of its glass bakeware in the 1980s.
  4. Currently, Pyrex bakeware made for use in the United States is made of tempered soda-lime glass. Soda-lime glass is less likely to break when dropped or bumped. Even though it is tempered, soda-lime glass does not withstand thermal shock as well as borosilicate glass.
  5. Pyrex bakeware made and sold in Europe continues to be made of borosilicate glass.
  6. Consumer Reports tests indicate that new borosilicate glass withstands thermal shock better than soda-lime glass, but seems to have an upper temperature limit of 500°F. Older borosilicate glass, in good condition, seems to withstand thermal shock even at 500°F.
  7. Soda-lime glass is easier to melt, results in fewer deformities, and produces fewer emissions than borosilicate glass. Soda-lime furnaces last longer and need less energy to run.
  8. There are hundreds of reported cases of Pyrex bakeware shattering. There are over 370 million pieces of Pyrex in use in American households.

I have some of the older, borosilicate Pyrex in good condition, so I feel relatively safe using it. After all, I’ve used it for over 35 years. However, just for a lark, I read the safety guidelines that accompany new Pyrex bakeware. Holy Cow! There are several things I do that are no-no’s. Some of the guidelines are even counter-intuitive. So, here are today’s Pyrex safety highlights:

  1. AVOID severe hot to cold temperature changes.
  2. DO NOT add liquid to hot glassware.
  3. DO NOT place hot glassware on a wet or cool surface, directly on countertop or metal surface, on a stove burner or metal trivet, on wet cloth or wet potholder, or in sink.
  4. DO NOT handle hot glassware—including bakeware with silicone gripping surfaces—with a wet cloth or wet potholder.
  5. DO NOT use with a direct flame including on a stove top, under a broiler, on a grill, or in a toaster oven.
  6. DO NOT use glassware to microwave popcorn or foods wrapped in special browning wrappers.
  7. DO NOT heat empty or nearly empty glassware in microwave, or overheat oil or butter in the microwave.
  8. DO NOT use or repair any glassware that is chipped, cracked, or severely scratched.
  9. DO NOT take dishes directly from the freezer to the oven or vice versa.
  10. ALWAYS preheat oven before inserting glassware.
  11. ALWAYS add liquid to cover the bottom of the dish before cooking foods that may release liquid.

You can find complete safety warnings at the Pyrex website, here.

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  1. Lindsay says:

    They might as well have added, DO NOT use Pyrex.

    Just kidding. Kindof. I found a European made one at a flea market once and passed. I’m thinking I should have gotten it after seeing this!

    Thanks for posting this, I know I’ve done a bunch of those No-No’s.

  2. bonita says:

    Amplification: Most (all?) of the sudden breakage reports involve clear glass bakeware. Patterned or colorful pyrex seem to be immune, probably because they have slipped into the classification “vintage.” Yes, dear readers:
    DO NOT leave your patterned or colored pyrex alone at a pot luck dinner. It won’t explode, but it may sprout legs and walk! Don’t believe me? Check out Pyrex: The Unauthorized Collector’s Guide on Amazon or the site Pyrex Love— these people give the term ‘collector’ a run for its money!

  3. Patrice says:

    Great post. I use Pyrex all the time at home. I have had breaks, but I always assume that I had probably bumped the piece earlier. I’m glad you printed the things to avoid at the end. Many of them made sense, but some I never dreamed of like the silicone pot holders. I’m not getting rid of it, but I will certainly handle it a bit more carefully.

  4. brookdale says:

    So, what DO you set the pan on when you take it out of the oven?
    This is scary! Thanks so much for posting this.
    (Just one more thing to worry about.)
    Luckily all of my Pyrex is “vintage”, from the 1960’s or before, I think.

  5. Ross says:

    Use a cooling rack for a place for hot glass.
    The only plce this would trouble me is with frozen pies which must go directly into the oven. So I guess I have to start looking for corningware pie plates or the olt metal ones.

  6. Sundownr says:

    I have a couple Pyrex dishes from the late ’80s and early ’90s. I guess I’m very lucky that I have a huge wooden trivet that I set everything on immediately from the oven. Before that, it was always the stove top!

    Thank you very much for the information!!

  7. Julie Hardie says:

    Oh my gosh that happened to me! I thought I did something to it to make it explode like that! WOW! I didn’t even think to google it or anything! After I had taken it out of the oven, I placed it on top and let it cool some. Took the food out and had dinner, then went to start the cleaning process. I had just picked it up and placed it on the cutting board and bam! it exploded. creepy!!

  8. Jessica Tibbetts says:

    OOO! My husband used my pyrex loaf pan as the dish he poured water into for the 5 minute bread he makes so well. He usually uses a metal loaf pan, but he couldn’t find it. The pan needed to sit in the 450 oven while it came to temp. When the water hit it BLAM! (is that a word?) shards of glass everywhere. Even in the drawer beneath the oven. Definately learned a DON”T that day.

    I take it as a positive because I’ve been wanting a cast iron one for awhile now. Now I have a reason…

    I usually set whatever comes out of the oven onto the stovetop that has been warming during the baking process. I guess that is why I’ve never experienced an explosion???

  9. NorthCountryGirl says:

    This is not Pyrex but just in interesting note. I have sets of Corelle dishes by Corning that I love. They are supposed to withstand breakage. I can drop them on the floor and even have on really hard surfaces and they don’t break. BUT, let me drop them on a rug or a relatively soft surface and once in a great while they will literally explode. It’s so weird. Has happened maybe two or three times in many years but for some reason, the hard drops don’t phase them but a relatively soft drop that even a glass dish would survive will shatter them. Must be hitting at the right angle at the right height at the right temperature, who knows?

  10. Neekyme says:

    Oh yeah – my cobolt blue pan exploded! It was my fault though, I turned on the wrong stove burner (which happened to be the one the pyrex was sitting on) and when I realized it I pulled the pyrex over to the cool burner – in about 3 minutes I had shards of blue glass everywhere! Thankfully my daughter in her baby walker and I were spared getting hit by the shrapnel somehow.

    Just recently I did the same thing – turned on the wrong burner, which had a pyrex pan with a few scraps of brownies left in it, on it – I quickly put it on an oven mit and put it in the oven in case it was going to explode too. It never did explode and cooled down fine on it’s own.

  11. Pete says:

    Thanks for the reminders – great post!!

    The easiest way to remember how to treat glass bakeware properly is to never allow it to be subjected to temperature shocks. That translates to NEVER place it damp into an oven, NEVER touching it with anything damp when it is hot, etc, or doing anything else to it or with it that can cause a quick temp change on one spot/area.

    Hot glass cookware (including canning jars) always go onto a wooden cutting board to cool in this house. Not always necessary, but it is easier for me to remember to do it when it is necessary by doing it with everything glass.

    Am guessing that the reason to not place Pyrex et al on the stove top to cool is because the metal burner grates will cool at a different rate than the air around them, producing yet another potential for thermal shock. We have all probably done that one, though! Probably not so bad if they are only there briefly and the oven is still on.

  12. BethieofVA says:

    This happened to a 9×13 baking dish at a pot luck I was attending. The woman had brought it from home placed on the table and kaboom! It just fell apart really, in many shards.

  13. Patricialynn says:

    Huh, and I thought it was just me!

    Years ago (when I was a new mother and new to cooking on my own), I tried making oatmeal in a Pyrex saucepan. I boiled the water in it, and then began to shake out some cinnamon. The MOMENT the cinnamon touched the water, the saucepan blew apart with violence. I ended up with about eight cuts (fortunately not very deep) and a couple of minor burns from the hot water.

    At the time I thought it was just my ignorance of cooking – perhaps I was’t supposed to boil fluids in such a saucepan? So I stuck with normal non-stick pans, cast-iron skillets, and stainless steel pans ever since.

    Perhaps now I will feel safe trying out Pyrex again – but ONLY the older stuff.

  14. Sheila41 says:

    I’ve never had any glass bakeware explode on me , but I am guilty of setting it on the stove top after I’ve taken it out of the oven , I guess I won’t do that anymore , I’ll just start using a towel or my wire rack from now on LOL.

  15. whaledancer says:

    Hmmm, I just got a couple of new Pyrex baking dishes for Christmas; I’ll have to remember to be very careful. I DID notice all the warnings on them.

    The one I can’t figure out is that they really stress never putting it in a cold oven and allowing it to heat; put it only into a preheated oven. It seems like that would be a bigger thermal shock. Weird. But I’ll do as they say.

  16. bonita says:

    @whaledancer, that’s exactly the one I found counterintuitive—I checked several places to make sure I had read the rule correctly. It just seems so odd!

  17. Darlene in North GA says:

    @Jessica Tibbetts: Please note, do NOT add cold water to a hot cast iron pot/pan. It WILL crack it. Had a friend that it happened to. I make Artisan Bread in 5 minutes too. I use the broiler pan that came with my oven for the pan to add water for steam. Or use an old pie plate/bread pan etc. I say old because I notice that my broiler pan is starting to get rust in the area where the water is constantly hitting it. I think the constant shock of being 450 degrees and getting hit with cold/cool/warm water has messed with the tempering and allowing it to rust.

  18. JoJo says:

    I was reading this to my husband and was amazed at all the things you [shouldn’t] sit the glass on when my husband blurted out “JUST HOLD UNTIL COOL.” I laughed out loud and thought well, that’s just about a true statement.

  19. Cassie says:

    I had a blue pyrex baking pan (like the one pictured above) shatter. What a mess. Thank goodness no one was in the kitchen. In my case a burner was still on when I set the pan down and I didn’t realize it. So it’s my own fault but still, I was shocked that it exploded.

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