Are Vintage Pyrex Dishes Microwave-Safe? Here's How To Check

One of our favorite kitchen-design trends for 2025 is retro decor with its eclectic warmth and nostalgia. It's a popular approach lately, which is why vintage Pyrex is currently very in demand. People are scouring flea markets, vintage shops, and online resale sites for hardy pans, cups, dishes, and more, often with country-chic patterns. The thing about vintage kitchenware is that once you've got it, you actually want to use it. And when companies are over 100 years old like Pyrex is, there are bound to be formulation changes, plus you don't get a handy guide when you buy things secondhand. That's why it pays to brush up on the history of vintage cookware — it's an issue of safety. For example, is vintage Pyrex microwave-safe?

Pyrex made in recently will have a stamp on the bottom marketing them microwave-safe, vintage Pyrex won't have that. But in general, Pyrex's whole claim to fame is how heat-resistant it is. We know it's not dangerous to put Pyrex in the oven; Pyrex is suited for the heat of the microwave, too. Of course, there are no guarantees with anything vintage. We can't know how well things were treated before we bought them. You're always taking a chance when you microwave Pyrex — it should be fine, but be aware. That said, if your Pyrex has metal in its pattern — some have lovely gold-leaf touches — it's a microwave no-go, as that could cause fire.

Pyrex was founded in 1915, produced by Corning Glass Works. Borosilicate glass, which is resistant to heat and extreme temperature shifts, was invented in the late 1800s in Germany. Corning perfected its own borosilicate process, and an employee's wife happened to use a borosilicate jar for baking, giving Corning the idea to launch a cookware line with the revolutionary material. As patents expired over the years, Corning had to keep developing tweaked recipes for their glass. One solution was to use tempered soda-lime glass. Soda-lime is the glass we see everywhere in everything — it's cheaper than borosilicate — and tempering is heat-treating it for durability. In 1998, Corning licensed Pyrex to Corelle Brands, and ever since, Pyrex has been made from tempered glass. It can be less heat-resistant than borosilicate and is definitely not as resistant to sudden temperature changes — that's why today's Pyrex needs to be at room temperature before going into the oven.

To figure out what your Pyrex is made from, no matter its age, look at how Pyrex is written on it. If it's all lowercase, "pyrex," it's likely tempered glass — Corning sold this trademark so it can be made by other companies. If it's all uppercase, "PYREX," it's the brand's own borosilicate glass. The former may very well not fare so great in the microwave, whereas the latter should be fine — it's also more likely to be vintage.