Fire King vs Pyrex

If you’ve ever browsed vintage kitchenware, you’ve probably seen the names Fire-King and Pyrex. But what’s the difference?
Both were kitchen staples in the mid-20th century, but here’s how they differ:
Pyrex was born first, launched by Corning in 1915. Early Pyrex was made of borosilicate glass, famous for withstanding extreme temperature changes—perfect for moving from oven to fridge without cracking. Later Pyrex (especially modern) switched to soda-lime glass, which is less resistant to thermal shock but cheaper to produce.
Fire-King, made by Anchor Hocking, came along in 1942. It used soda-lime glass from the start, but what it lacked in chemistry class, it made up for in charm with unique colors like jadeite and peach luster, or sweet floral decals like Primrose and Fleurette.
Want a quick trick to spot vintage Pyrex? Look for the all-caps PYREX mark; those are the early borosilicate pieces!
Meanwhile, Fire-King jadeite has a fan club all its own—especially after Martha Stewart showed it off in the '90s, turning humble diner mugs into must-have collectibles.