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eppur_se_muova's Journal
Posted by eppur_se_muova in General Discussion
Tue Jan 18th 2011, 02:36 PM
Just read this article this morning while waiting in the doctor's office. Short version: "Pyrex" made in the USA is no longer borosilicate glass, which has a low coefficient of thermal expansion and is therefore much less prone to break on rapid heating or cooling (lab glassware is mostly borosilicate). Pyrex made in Europe is borosilicate. CR lab tests showed the American products were more likely to shatter due to thermal shock under conditions likely to be encountered in a normal kitchen, and recommended the Consumer Products Safety Commission (CPSC) investigate the issue.

Corning sold its U.S. Pyrex production to World Kitchen in 1998, but may have stopped using borosilicate before that date -- it is not clear, and the companies involved make contradictory statements. Apparently borosilicate (which melts at higher temps) would have required more pollution controls, so mfgrs turned to lower-melting soda-lime glass, the cheapest kind, instead, and use heat-tempering to produce a stronger product, but not one with the same heat resistance as borosilicate.

I foolishly thought that Pyrex was an identifier specifically for borosilicate glass; apparently it is just a brand name, and can be applied to whatever its owner wishes.

"The baking dish just exploded as my daughter was about to touch it, sending pieces of glass and hot juices from the ham flying everywhere," says Szczcenia, 63. "We had splash burns on our arms and the tops of our legs, and my 3-year-old granddaughter stepped on a piece of glass before I could get her out of the kitchen. I can't begin to tell you how scary it was."

She filed a report with the Consumer Product Safety Commission and contacted the manufacturer. The company said it is possible that she had not followed the bakeware's instructions and that it could not confirm that the product was Pyrex because she had not sent the shards for the company to examine. Szczcenia says she has no doubt the dish that shattered was Pyrex because she'd just purchased it for her daughter a few weeks earlier, and as a loyal Pyrex customer for 30 years, she always looked for that label.

"I loved my old Pyrex, and I certainly know how to use it properly," she says, "but it seems like the only correct instructions for this new Pyrex would be not to use the dish near heat at all."
***
In recent years, news reports and Internet postings about glass bakeware unexpectedly shattering have some consumers worried about safety and confused about instructions. Packaging may prominently say freezer-safe and oven-safe. But consumers might not be aware of warnings which can appear on the back of a label in type this small with cautions about preheating the oven, cooling, use of liquids in the pan, and more.
***
more: http://www.consumerreports.org/cro/magazin...

I first became aware of this issue through this posting on DU (I think there might have been a couple of others at about the same time). Note that this is about Corning Ware, not Pyrex, but the issue of an inferior product being sold under an established, trusted brand name is the same:
http://www.democraticunderground.com/discu...

My sister bought a lot of Corning Ware through Craigslist at about the same time, and after comparison with my Mom's cookware, we found that some of the older dishes are marked "for range and microwave" while the very oldest (pre-microwave) are unmarked. Some of the newer pieces in our kitchens are labeled for stovetop use, but not microwave. Others have only the Corning Ware mark, and one includes the word "Pyroceram". Probably best not to assume it is microwave- or broiler-safe if it is not clearly marked as such, at least if it is newer.

Here are some posts by DUers who experienced these problems first hand:

http://www.democraticunderground.com/discu...

http://www.democraticunderground.com/discu...

http://www.democraticunderground.com/discu...




ETA: a Googlon for other sources/citations ...
http://www.google.com/search?q=consumer+re...



ETAA: wikis (needing cleanup/citations):
http://en.wikipedia.org/wiki/Borosilicate_...
http://en.wikipedia.org/wiki/Tempered_glas...
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