Be Careful When You Use a Glass Baking Tray: The Difference Between Pyrex and PYREX That Many People Miss

Glass baking dishes are kitchen staples. They go from oven to table, look sturdy, and feel trustworthy. But there’s a little detail stamped on the bottom that many people overlook—the difference between “Pyrex” and “PYREX.” That tiny change in lettering can matter more than you think.

Understanding it can help you avoid cracked dishes, shattered glass, and kitchen accidents.

Why the Name Looks the Same—but Isn’t

At first glance, Pyrex and PYREX seem identical. For decades, people assumed they were made the same way and could be used interchangeably. In reality, the difference often comes down to the type of glass used, which affects how the dish reacts to heat.

Pyrex (Lowercase “e”)

Traditionally, Pyrex with a lowercase “e” was made from borosilicate glass. This type of glass is:

• Highly resistant to thermal shock

• Better at handling sudden temperature changes

• Commonly found in older or European-made cookware

Borosilicate glass expands and contracts slowly, making it safer when moving between hot and cool environments.

PYREX (All Caps)

In many regions—especially in the U.S.—PYREX in all capital letters is often made from tempered soda-lime glass. This glass is:

• Stronger against drops and impacts

• Less resistant to sudden temperature changes

• More likely to shatter if exposed to rapid heat shifts

Tempered soda-lime glass is durable, but it doesn’t tolerate thermal shock as well as borosilicate.

Why This Difference Matters in the Kitchen

Most glass-baking accidents don’t happen from normal use—they happen during temperature changes, such as: