Factless

You see since 1998 when Corning Glass spun off the Pyrex kitchenware division to World Kitchen company which no longer uses borosilicate glass, which is what gave Pyrex its thermal shock resistance.

This thermal shock resistance is one of the biggest factors the Pyrex brand became famous and synonymous with quality glassware, in both the lab and the kitchen.

Now World Kitchen uses regular soda-lime glass that is tempered for increased strength in their kitchenware glass products, which is not as shock resistant, as my father strikingly demonstrated for me the last time I was home to visit.

So, yet again another case of they don't make it like they use to. For the worst, as far as the customer or cook is concerned.