What’s the Difference Between PYREX and pyrex?

There is a big difference between PYREX and pyrex, even though they look almost identical — and no, we’re not just talking about capitalization. The lettering on your glassware may seem minor, but it can have significant safety implications in your kitchen. So, what’s the actual difference between these two terms, and how can it affect your cookware’s performance? Keep reading to find out.

By Editorial Team
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A Trusted Kitchen Brand

Pyrex has long been known as a trusted name in kitchen glassware, celebrated for its durability and heat resistance. However, in recent years, videos of glass dishes unexpectedly shattering have gone viral, prompting many to ask: What changed?

Is there truly a difference between “PYREX” and “pyrex”? And more importantly, how can you tell which one you own?

What Is Pyrex?

To understand the difference, let’s take a step back and explore the types of glass commonly used in kitchenware: borosilicate, soda-lime, and tempered glass.

Borosilicate glass contains boron trioxide, a compound that dramatically reduces thermal expansion. This means borosilicate glass can withstand rapid temperature changes—like moving from the fridge straight to a hot oven—without shattering. Pyrex was originally made from borosilicate glass.

In contrast, soda-lime glass is the most common glass used in drinkware and other household items. It’s not as resistant to thermal shock, especially if untreated. When soda-lime glass is heat-treated, it becomes tempered glass, which is stronger and more durable—but still not as heat-resistant as borosilicate.