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Certain glass bakeware can explode when hot

December 7, 2010 12:00:00 AM PST
Glass bakeware, such as Pyrex and Anchor Hocking, are staples in many kitchens. The companies' marketing touts how versatile they are - good for ovens and freezers. While hundreds of millions of dishes are used safely each year, a year-long investigation finds that hot glassware can shatter unexpectedly. Patricia Szczcenia says three years ago on Thanksgiving she went to baste a ham that was roasting in a Pyrex dish, and was stunned at what happened next.

"It exploded. I mean all over the kitchen. I mean, there were glass shards from wall to wall," said Szczcenia.

Pyrex says it can't confirm the kind of glassware Szczcenia was using because she didn't send the shards to the company. Consumer Reports' Andrea Rock investigated her case, along with 151 other incidents involving glass bakeware that have been reported to the Consumer Product Safety Commission.

The issue seems to be a type of glass that's more environmentally-friendly to produce and less expensive.

"Pyrex has changed over the years. It used to be made of a type of glass called borosilicate. And so did Anchor Hocking bakeware. Now they're both made of a kind of glass called soda lime," said Rock.

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 brand new 13-by-9-inch bakeware from Pyrex and Anchor Hocking -- both made of soda lime glass -- as well as European-made Pyrex and Arcuisine Elegance bakeware made of borosilicate. All have warnings to avoid extreme temperature changes, and packaging on the American-made products contain a lot more cautions in small print.

"Our test was contrary to the instructions, but we 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," said Rock.

In Consumer Reports' tough lab tests, the glassware was filled with dry sand, which gets far hotter than food. It was put in a 450-degree oven for 80 minutes, then placed on a wet granite countertop - something you're not supposed to do.

Ten out of 10 times the soda lime glass broke. But in the same conditions, the European glassware did not break, though most did after baking at 500 degrees.

The American manufacturers say soda lime glass has advantages and is less likely to break when dropped or bumped.

"Our advice is follow directions carefully," said Rock.

You should use metal pans, if you want to avoid risk entirely.

Both 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 with your cookware, you can report the incident to the CPSC at (800) 638-2772 or info@cpsc.gov.

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