Have you ever heard of Pyrex baking dishes breaking for no apparent reason? My son had one "spontaneously" explode earlier this year, and I have wondered about it ever since. Well, this morning while cruising the news sites I ran across this article and found my likely answer:
Kitchen calamity: Reports of shattering cookware on the rise
In an apparent cost cutting measure World Kitchens, the current owner of the Pyrex brand changed the composition of the glass in their products. They are no longer using Borosilicate Glass in their bakeware, now it's a Soda-Lime-Silicate composition. They also are not alone in making this move. Anchor Hocking has also made this switch, and even has a page on their site explaining the difference with some cautions.
I'm no glass expert, but I do know that most all glass labware is still made from Borosilicate glass. If the Soda-Lime-Silicate product was "just as good" why wouldn't it go straight from kitchen to lab products? We all know the answer, because it is inferior. Here's a page on glass types from Rutgers University, Topics in Materials Science. The takeaway is these statements:
...addition of borates allows one to use less alkali (such as soda and potash) in the glass which is often desirable, as alkali fluxes significantly decrease mechanical strength...
Emphasis by the diarist, and
The addition of borates also contributes significantly to the chemical durability (as in the case of sodium vapor lamp encasements) and reduced thermal expansion (in the case of Pyrex glassware).
Emphasis again by the diarist
So, if you are cooking with Pyrex or Anchor Hocking glassware, be aware that it isn't your Grandma's Pyrex, and you better be careful!
Action: At the World Kitchens site above there is a contact link. I sent them a message indicating I will never buy a Pyrex product again. Going the way of the cheap is not a good business move, and if enough people express their displeasure, maybe we can make them change.