A Pyrex liquid measuring cup is one of those things most people have in their kitchen, and many of those measuring cups date back to the 1950s. What most people don’t notice about the glass measuring cups with the red markings is the logo. There’s actually a difference between PYREX with capital letters and pyrex with lowercase letters. Corning invented the brand Pyrex in 1915 and made all Pyrex products — casserole dishes, loaf pans, pie pans — with borosilicate glass. This type of glass has an element called boron trioxide in it, which makes it highly resistant to major temperature changes, reducing the risk of breaking. Products labeled PYREX in Europe, Africa, and the Middle East are still made with borosilicate glass, but products made in the rest of North America, South America, and Asia are no longer made with borosilicate glass. They are made with tempered soda-lime glass, which is heated and cooled in a manner that makes it more durable than regular glass under temperature fluctuations. Pyrex products made with soda-lime glass now contain the logo in small letters. While soda-lime glass is still heat-resistant, it’s not quite as heat-resistant as borosilicate glass. Since PYREX is made with borosilicate glass and is more heat-resistant, it's less prone to breaking due to any sudden changes of temperature such as transferring a casserole from the refrigerator directly to the oven. That makes PYREX cookware safer than pyrex cookware, which runs a higher risk of exploding due to thermal shock (when the glass goes through an extreme temperature change that can cause it to fracture). Regardless of whether you own PYREX or pyrex cookware, it's important to care for them properly so that they don’t break.
- • Always avoid sudden drastic changes in temperature.
- • Don’t pour boiling liquid into it.
- • Let it cool down after pulling it from the oven before running cold water over it in the kitchen sink.
- • Don’t put frozen or refrigerated casseroles or pies straight from the freezer into a hot oven.
- • Don’t put your cookware directly under the broiler.
- • Always store the baking dishes carefully to prevent micro-cracks in the glass, which can weaken them.
