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Feb 26, 2008 10:36 pm US/Central
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Testing Pyrex: Experts Weigh In
CHICAGO (CBS) ―
CBS 2 has discovered more than 300 complaints from people who say they cooked with Pyrex and say their bakeware has shattered or even exploded in the kitchen. Is there a problem with Pyrex?
CBS 2 Investigator Pam Zekman reports that World Kitchen, the maker of Pyrex, says no.
World Kitchen says the complaints the 2 Investigators found are unsubstantiated and very limited compared to the 369 million pieces of Pyrex sold since it bought the brand from Corning 10 years ago. And the company commissioned a test to help prove the product is safe.
But first, here is what one consumer told CBS 2:
"It sounded like a shotgun went off. A loud explosion," said home cook Terry Rhoads.
That's how he describes what happened after he transferred a hot Pyrex pan from an oven to a countertop after melting butter to make cornbread.
"I looked down and that's when I saw about an inch and a half long piece of glass projecting out of the top of my foot," Rhoads said.
The 2 Investigators asked World Kitchen for the results of its own quality assurance and product testing. The company said those results are a trade secret.
But to satisfy our request World Kitchen said it hired a well-respected independent company, Exponent, to test how Pyrex reacts to what World Kitchen called "extreme induced thermal shock conditions."
To do it Exponent intentionally violated instructions on the label that comes with Pyrex products.
Those instructions say you should "avoid severe temperature changes. Do not add liquid to hot dish... place on cold or wet surfaces. And do not use any item... that is scratched."
In a report Exponent describes how it tested seven dishes taken from a 450-degree oven and placed on a wet towel to induce shock.
Three dishes did not break, even after water was poured on them.
Exponent severely scratched four other dishes with a sanding disk before heating them.
Two of those fractured when placed on the wet towel, but Exponent reported the "velocity and energy were very low" and the furthest a piece traveled was "about one foot."
World Kitchen says the Exponent test showed that "the damage from the forced breakage was not sufficient to cause injury."
Rhoads' experience was different.
"The velocity was high enough to embed that piece in my foot," he said.
He required surgery to repair a ruptured tendon in his left foot.
"It also went far further than one foot," Rhoads said. "It traveled eight or nine feet across the kitchen."
CBS2 asked glass experts with doctorate degrees in material science who specialize in glass to review the exponent report.
"I think there are some flaws in their testing procedure. First of all they tested very few specimens," said Stephen Freiman, Ph.D. "Secondly they tested empty Pyrex dishes," instead of dishes with something in them.
"It keeps the heat inside and allows the outside to cool and that's what generates the stresses that cause the fracture problem in the first place," he added.
As for placing the hot dish on a wet cloth, Prof. Richard C. Bradt, Ph.D. of the University of Alabama said, "The soft wet cloth will absorb the energy from the fracture process and then it cannot go in to propelling the shards across the room."
Another flaw according to the experts was scratching the dishes before heating them.
"There's not very much strain energy and the shards don't get propelled very far," Bradt said.
"In fact they made it almost impossible for any pieces to fly," said Prof. Jack Mecholsky, Ph.D., of the University of Florida. "They guaranteed that there would be low strength breaks."
Mecholsky has been hired as a consulting expert in a lawsuit against World Kitchen involving a product other than Pyrex. World Kitchen says this shows his views are biased. However his opinions are generally consistent with those of other experts CBS 2 consulted
World Kitchen did not accept the 2 Investigators' repeated requests for an on-camera interview. But, in a letter to CBS 2, the company said "changing these details would not result in glass fragments being projected much differently."
"One test is worth a thousand expert opinions," said Professor Sheldon Mostovoy, Ph.D. of the Illinois Institute of Technology.
Mostovoy wanted to do his own experiment before commenting on the Exponent test.
He followed Exponent's example by testing how Pyrex dishes reacted when subjected to extreme misuse.
In a report Mostovoy describes how he tested eight dishes in a 450-degree oven, like Exponent.
Like Exponent, he severely scratched one dish to demonstrate how that can lower its energy. He scribed it with a glass cutter before heating it and then placing it on a wet metal surface.
"The part just fell off. It didn't get thrown at all," Mostovoy said.
Unlike in Exponent's tests, all the dishes were placed on a hard surface instead of a cloth.
Two unscratched dishes placed on a dry metal surface did not fracture. Two other unscratched dishes placed on a wet metal surface did break but with little force.
Mostovoy then tested unscratched dishes filled with sand to simulate food left too long in the oven -- another potential abuse.
Two fractured, sending shards about three feet.
And when a third dish was placed on a wet granite tile, "It exploded. And it threw a piece somewhere on the order of six to eight feet away," Mostovoy said.
Even so, Mostovoy believes Pyrex is safe. But the instructions on the cook ware label are not adequate.
"It requires now a great deal of care on the part of a homemaker to be sure they follow the instructions to the letter," Mostovoy said.
But, he also believes the instructions don't adequately warn cooks about the danger of placing a hot dish on anything but a dry soft surface like potholders.
"I believe they should have it in big letters," he said.
World Kitchen criticized Mostovoy's test saying "it does not accurately demonstrate or depict the actual performance of bakeware used in American kitchens."
The company says Rhoads' mistake was placing a hot dish on a cold surface. But the instructions don't specifically say a countertop qualifies as cold.
A company spokesman told Rhoads it does not recommend preheating a Pyrex dish with just butter or oil inside; that could cause uneven hotspots and could cause dish failure.
But the instructions that come with Pyrex only warn "do not overheat oil or butter in microwave." The oven is not mentioned.
There are a lot of warnings that most people would not know how to follow," Mecholsky said.
Now, Terry and Julia Rhoads no longer cook with Pyrex.
"Our confidence is gone," they said.
World Kitchen defends the instructions on Pyrex as robust and specific and says the label adequately informs cooks about the kind of misuse that can lead to breakage. The company points to the most recent two years of data from the Consumer Product Safety Commission. It shows no emergency room treatment for injuries from shattered Pyrex.
A spokesperson for the CPSC told the 2 Investigators it does not consider Pyrex to be a safety hazard. The bottom line: the company says that Pyrex has an excellent safety record
So why are cooks still having some problems with Pyrex? Wednesday at 10 p.m., Pam Zekman will have a report on what our experts think is going on.
If you have something you'd like to share about an experience with Pyrex,
e-mail us.
Click here for a link to the Pyrex Web site.
Click here for a link the Consumer Product Safety Commission.
Read the first part of "A Problem With Pyrex"
here.
(© MMVIII, CBS Broadcasting Inc. All Rights Reserved.)
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