On 08/22/2014 12:41 PM, Paul Drahn wrote:
....

As I recall reading a few years ago, today's Pyrex is not your
Grandmother's Pyrex. The company changed hands and today's Pyrex is no
longer tempered glass.

It's tempered glass all right, just not _borosilicate_ glass of the
original Corning products. The trademark has been licensed to several
manufacturers, a few of the smaller of which still do use borosilicate
glass but the primary one doesn't. World Kitchen iirc is the spinoff of
Corning that uses a clear tempered soda-lime glass instead because it's
less expensive. It also isn't as heat-stress resistant and there've
been some complaints...

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