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Consumer Reports Investigates Exploding Pyrex

The new January, 2011 issue of Consumer Reports has a five page spread on "Glass bakeware that shatters." While they stopped short of saying not to buy the stuff, it's pretty clear that there are serious safety hazards with Pyrex and Anchor Hocking products. Cookware discussion boards have been covering this for the past few years. It's nice to see CR researching the topic too. This article is not online yet, but should be soon.

I believed the cooks who posted their experiences with shattering glassware in spite of the exhaustive denials by the manufacturers. They are still denying responsibility to the CR investigators.

To be safe, I simply quit using transparent glass for any heating applications. Good quality stoneware and porcelain have replaced Pyrex for me. With careful shopping online and in TJX stores, it wasn't that expensive.

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  1. There may be problems with current production, but the world is full of Pyrex and Fire-King that have not exploded or shattered in decades of use. It's pretty useful stuff -- versatile, durable, and very inexpensive. Look for it in the second-hand market.

    2 Replies
    1. re: ellabee

      Since we're talking about glass and ceramic breaking due to heat stress, here's another story: I took a hot steamy wet lid off a pan and set it on my glass cooktop flat so that it created a suction strong enough to crack the cooktop its entire diagonal length. We had to replace the cooktop. Now I set the lid down at the edge so air can get up under it.

      1. re: Querencia

        *that* is crazy...I absolutely believe you, but whoddathunkit? (if I stop and think about it logically, yes, it can happen...but I don't think I would have given it any thought in the heat of the moment.)

    2. I had a glass bakeware product disintegrate in my hands. I took the glass out of the oven and it literally shattered in my hands. There was glass everywhere. Fortunately I was able to clean up and no harm was done to me....but I'm retiring the rest of my glass bakeware after the report in consumer reports. It is not worth taking a chance that the next time something happens the glass shatters and winds up in my eye or some other bad scenario. When the baking dish shattered I thought it was a defective dish and did nothing; but now that it has happened to many others, I'm not willing to take the risk any more.

      1. I wonder if they're not making Pyrex like they used to. I've got several Pyrex pieces that get used in the oven quite often; they must be 30+ years old, and I've never had a problem. Maybe they've changed the composition of the glass in recent years.

        7 Replies
        1. re: CindyJ

          Pyrex in US used to be made of borosilicate glass, now the Pyrex bakeware you see are made with soda lime glass. The Pyrex lab glassware are still made with borosilicate glass.

          http://www.amazon.com/PYREX-Brand-432...

          In short borosilicate glass has a very low thermal expansion coefficient which is why scientists have little problem using these borosilicate lab glassware for chemical reactions. Not to say they will never break, but they are resistant to thermal shock. Soda lime glass is not. Therefore you hear all these US Pyrex bakeware breaking.

          I kept saying US Pyrex, because European Pyrex are still made with borosilicate glass.

          1. re: Chemicalkinetics

            Thank you very much for the explanation and link.

            1. re: Chemicalkinetics

              What what about impact? Cast iron sink, marble pastry board, granite counters... there are lots of unforgiving surfaces in a kitchen. Which type of glass is less fragile when it comes to being dropped or hit?

              1. re: KansasKate

                Great question, and I assume you actual know the answer as well. :)

                That is World Kitchen (maker of US Pyrex) major defense. Although soda lime glass is worse than borosilicate in term of thermal shock resistance, soda lime glass is better in term of physical impact resistance.

                1. re: Chemicalkinetics

                  Huh?

                  I'm a glass artist, and I work with both soda-lime (104 coe) and boro. I've never heard of, nor experienced this claim of soda-lime glass having more impact resistance than borosilicate.

                  Not saying it's not true, but I've been melting glass for years, and in my experience, boro is the tougher glass in pretty much all applications involving impact. Most of my experience is with "accidental concrete floor droppage" or "fling-age", mind you.....not exactly peer-reviewed science:)

                  1. re: SherBel

                    The soda lime glass in Pyrex products have been strengthened/tempered after forming to increase their impact resistance. That does not mean that it the glass has been toughened to be more impact resistant than borosilicate, but that the performance of their glass may be different than the performance of the soda-lime glass that you work with.

                    Anecdotal evidence aside, I would imagine that their bean counters and insurance adjusters ran the numbers of liability from injury of borosilicate breaking from impact vs tempered soda-lime breaking from thermal expansion, and the numbers (after factoring in cost of re-tooling the production line and differences of ongoing cost of materials) came out in favour of continuing use of soda-lime.

                  2. re: Chemicalkinetics

                    Count me as someone who would much prefer thermal sturdiness.

                    I would be much more upset if my Mac and cheese exploded in my hands when I took it out of the oven than if I clumsily dropped a glass casserole dish onto my hard floor.

            2. Agreed about the older stuff, I have pieces of pyrex, mainly older oval casseroles that have been my go-to bakeware for over 20 years. I don't plan to quit using it because of an article in Consumer Reports, whom I love, but they're far from infallible.

              1 Reply
              1. re: EWSflash

                +1 - Mine are about 38 years old and still going strong.

              2. I have two pyrex baking dishes; one is 40 years old, the other about 25 years old in which have oven baked thousands of meals and baked goods and have microwaved an equal number of times. Perhaps it's because they're made with the old glass recipe, but there is no way I'm ditching them. Last year I replaced all my plastic storage containers with pyrex. They go from freezer to microwave to dishwasher repeatedly without incident. I just don't put them near wet or cold surfaces when hot. So far, very good.

                1 Reply
                1. re: Ambimom

                  I feel exactly the same way; my pan has got to have 20+ years on it, and is my go-to dish used many times per week. But I guess I ought to respect it more, since it looks like replacing it may be hard!