Date: Tue Oct 27 18:35:04 2009
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Subject: Re: Microwave pirex warning
I thought it was on tap-l, but now I think my older sister pointed
this out about pyrex:
PYREX isn't the pyrex is used to be. In order to reduce costs, the
Chinese, after purchasing the copyright modified the glass formula.
The new formula had defects which show up in microwave ovens in the
form of catastrophic failure. The new stuff has a "K" molded into the
glass (at least some of it does), and that means it is a time bomb
waiting to happen.
I understand this was snopes reviewed. Karl
Quoting "Zani, Gerald" :
> I agree with Bill.
> The plate was manufactured quickly. It was cooled quickly after it was
> formed and was never annealed.
> It was highly stressed, like a Prince Rupert's drop. The uneven heating
> in the uwave released the stress and caused a complete shattering into
> small bits. - jz
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Behalf Of Bill McNairy
> Sent: Tuesday, October 27, 2009 7:51 AM
> To: email@example.com
> Subject: Re: [tap-l] Microwave
> Many popcorn bags have 'heating' pads on the bottom surface (conductive
> inserts) that appear to heat the oil more evenly. If not present, then
> at least the 'congealed' oil will be at the bottom. As with conventional
> electrical poppers that use oil, this goop must be heated to the point
> where the water pressure in the corn kernels will exceed the
> constraining limit of the hull-- and the corn pops, with the superheated
> water quickly converting to steam that 'inflates' the corn starches into
> most delicious theater food.
> If the plate was unable to withstand the large stresses of localized
> heating of the oil to high temperatures near the center, and normal room
> temperatures further out, then the stresses could cause the plate to
> 'pop' into many pieces. Same thing would happen if the plate were
> uniformly heated in an oven, then placed in a sink and cold water were
> then poured over its center.
> Was the plate labeled 'microwave safe'?
> Pyrex would not have done this (unless it had a structural flaw).
> Robert T McQuaid wrote:
>> October 27, 2009
>> Subject: Microwave
>> My son has often heated macaroni by putting it on a
>> plate in a microwave oven. He has also cooked popcorn
>> in the microwave by putting in a pre-packaged bag.
>> Recently he changed the popcorn procedure by putting a
>> plate under the bag. At the point where the popping was
>> nearly complete the plate shattered. Not into a few
>> large pieces, but lots of small ones, none more than 5
>> per cent of the original size.
>> What happened to cause the plate to shatter?
>> Robert T McQuaid
>> Mattawa Ontario Canada
> Dr. William McNairy
> Phone: (919) 660-2689 FAX: (919) 660-2525
> Department of Physics, Duke University
> Room 184 Box 90305
> Science Drive Durham, NC 27708-0305
From firstname.lastname@example.org Tue Oct 27 18:35:04 2009