Pyrex and Anchor Hocking glassware have changed over the years. They used to be made of a type of glass called borosilicate. Now they're made of a kind of glass called soda lime. Consumer Reports tested both kinds of glass in its lab to see how they compare in extreme conditions likely to cause breakage.
The tests included new 13x9-inch bakeware from Pyrex and Anchor Hocking. European-made Pyrex and Arcuisine Elegance, made of borosilicate, were also in the tests. All have warnings to avoid extreme temperature changes, and packaging on the American-made products contains a lot more cautions in small print. The test was contrary to the instructions, but Consumer Reports set the bar high because people may not be aware of the instructions and dishes that are scratched or damaged may be more susceptible to shattering.
In Consumer Reports' very tough lab tests, the glassware was filled with dry sand, which gets far hotter than food. It was put in a 450° F oven for 80 minutes, then placed on a wet granite countertop, something you're not supposed to do. Ten out of ten times, the soda lime glass broke. But in the same conditions, the European glassware did not break, though most did after baking at 500° F.
The American manufacturers say soda lime glass has advantages and is less likely to break when it's dropped or bumped.
Consumer Reports' advice is to follow directions carefully. And use metal pans, if you want to avoid risk entirely.
Anchor Hocking and World Kitchen, which makes Pyrex in the U.S., say the number of breakage complaints they get from consumers involves a very tiny fraction of the hundreds of millions of pieces of glassware in American homes. But Consumer Reports says there are enough cases to warrant further investigation by the Consumer Product Safety Commission. If you have a problem, report the incident to the CPSC at 800-638-2772.
Consumer Reports' complete investigation of shattered bakeware is available at: www.consumerreports.org/cro/magazine-archive/2011/january/home-garden/glass-cookware/glass-cookware/index.htm.
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