Pyrex is supposed to be tough stuff, capable of withstanding extreme temperature changes, like a trip from the freezer to the oven. And that was true with old Pyrex, made from thermal-stress resistant borosilicate glass. But starting in 1994, Corning began licensing the name Pyrex to other manufacturers, which, today, make Pyrex brand cookware with a different chemical formulation—soda lime silicate glass. A report in the Bulletin of the American Ceramic Society says the new glass doesn't have the heat-protection powers of the old stuff. So why use it? Apparently, the manufacturers say soda lime silicate glass provides better protection against breaking when dropped. The report didn't test that, but this could just be an example of chemical trade-offs. Listen to Scientific American's podcast about this news. Or read the full report. (Via Christopher Mims)

21 Responses to “Time to start coveting vintage Pyrex”

  1. Joe Matise says:

    Not sure this really qualifies as news, this has been fairly well known for a couple of decades now… If my memory serves, Consumer Reports did a test a few years back to see how the new stuff did, and it did better than other brands in heat exchange but nothing like the borosilicate glass.

  2. Another great article talking about the trade-offs here- http://www.howtospotapsychopath.com/2012/02/09/is-pyrex-pyrex/

  3. “Time to start coveting…?”

    I never stopped…

  4. Robert Bosworth says:

    I made jello a few years back.  Poured the boiling red mixture into a pyrex container (I was pretty sure that what “Pyrex” was for?) and it exploded.  I’m still periodically finding sticky red goo behind cabinets or behind things hanging on my kitchen wall.  I found glass 15 feet away.  Haven’t bought another pyrex product since.

    • Gyrofrog says:

      But have you bought Jell-O since?

    • franko says:

      fwiw, don’t put it under the broiler, either. that’s how i ended up with molten, exploding tofu.

    • LinkMan says:

      My mother once exploded one of our pyrex casserole dishes.  She put it right under the broiler (with a very nice piece of fish).

      She went to pull it out of the oven a few minutes later and BOOM!   Tiny bits of glass everywhere.

      It did say “no stovetop, no broiler” on the dish itself, though.

      • Restless says:

        We had a Pyrex dish with a casserole in the oven at 350 degrees F.  It exploded.  In fact, it splintered; when I was trying to clean it up I had a pile of splinters shoving up under my fingernails, bamboo-torture style.

        I, too, refuse to buy any Pyrex anymore.  It’s all metal, all the time at my house now.

        • Daniel Saraga says:

          I think the trick is to not put it in a situation where it would experience extreme temperature variations in very short periods of time. E.g., a casserole stays warm from the oven to the stovetop, and its surface keeps the dish warm; an eggplant or a couple potatoes rolling around don’t provide the surface coverage for the dish, so the cool air surrounds the entire dish and cools it too quickly. crack. 

  5. Tom Williams says:

    those of us who make our own backyard wood fired pizza oven covet the old pyrex for its ability to be used in very very hot oven, as a substance to have light shining thru it it illuminate the oven.

  6. Atvaark says:

    I believe that in Europe, Pyrex objects are still made out of borosilicate.

    • esobocinski says:

      I’ve read that too. In Europe, Pyrex is licensed to Arc International, which chose to use the original Corning formula. In the US, Pyrex is licensed to World Kitchen which, as you might predict from the name, is committed to a cheaper imported product.

  7. KWillets says:

    This is pretty well-known.  The real borosilicate is used in things like wood stove doors and telescope mirrors.  I think those glass electric cooktops use it as well, and possibly some oven doors, but Pyrex stopped being Pyrex a long time ago.

  8. RJ says:

    You can still buy borosilicate lab glassware. A lot of it comes out of China, these days. If you check eBay, you can also easily get real Pyrex and Kimax stuff.

  9. arsphenamine says:

    Pyrex may be dead but borosilicate glassware not only survives but thrives.
    A search on “borosilicate glassware -pyrex” is all it takes.

  10. I fancy the not-quite labware from Catamount.  The gravy separator/strainer is especially indispensable.

  11. Ipo says:

    Apparently, the manufacturers say soda lime silicate glass provides better protection against breaking when dropped.
    I expect for glassware to break when dropped. 
    I don’t expect it to turn into 400 °F sharp shrapnel, or I wouldn’t be using it. 

  12. Church says:

    Wouldn’t this be a trademark violation? After all, preventing consumer confusion is supposed to be the point of trademarks.

    • Coderjoe says:

       I suppose it depends on who is doing the confusing. Since the trademark holder is licensing the name out, it is okay by the law.

  13. ntsteflonnts says:

    That’s why I always insist on Schott Duran for my thermoglass needs.

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