Start with a little history: Originally developed by Corning Inc. in 1915, PYREX (in uppercase) was made of borosilicate glass, a heat-resistant material that was ideal for use in the lab and kitchen.
Over time, owners and manufacturers have changed. Today, in the United States, most “pyrex” (tiny) glasses sold in stores are made of soda-lime glass, not borosilicate glass.
Borosilicate glass (PYREX) is more resistant to thermal shock, which means it is less likely to break when transferred from the freezer to the oven. Soda-lime glass (Pyrex), although cheaper to produce, is more sensitive to sudden temperature variations.
Serving and storage tips:
Use the original PYREX (borosilicate) for high-temperature applications such as baking or rotisserie, especially after transfer from a cool place.
Use modern pyrex (soda-lime) for cooking at room or moderate temperature, such as casseroles or storage containers.
Never expose the glasses (PYREX or pyrex) to direct heat from a stove or sudden changes in temperature.
