They Sure Don't Make Pyrex Like They Used To

[JBeukema]

Most people probably don’t think of Corning as a crime fighting company, but when it sold its Pyrex brand to World Kitchen in 1998, the company accidentally made the illegal manufacture of crack cocaine more difficult—a fascinating example of unintended consequences.
Ordinary glass shatters if it’s heated too quickly: Pour boiling water into a common flintglass tumbler, and it’s likely to fall apart seconds later. The glass on the inside expands when it gets hot, putting stress on the cold glass on the outside. When the stress gets too great, it cracks.
Pyrex, which originally was always borosilicate glass, solved this problem by adding boron to the silica (quartz), the main ingredient in all glass. Boron changes the atomic structure of glass so it stays roughly the same size regardless of its temperature. Little thermal expansion means little stress. Thus borosilicate glass withstands heat not because it’s stronger, but because it doesn’t need to be stronger.

Video: They Sure Don't Make Pyrex Like They Used To | Popular Science