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What’s The Difference Between PYREX And Pyrex?

There is a big difference between PYREX and pyrex even though they are spelt the same way — we're not talking about the capitalization. They appear on the glassware but there are consequences if they are spelt in uppercase or lowercase. What could be the difference between these terms and how can they affect safety in your kitchen? Keep reading to find out.

By Cookist

A great kitchen brand known for its longevity is the Pyrex brand. However, not too long ago, videos of dishes shattering became popular and it got us curious as to why the dishes were getting messed up that way.

It made us wonder if there was truly a difference between “PYREX” and “pyrex” as well as how a person can tell which one they have.

What Is Pyrex?


To understand what this is all about, we need to go back to the beginning. There are three basic types of glassware found in most home kitchens: soda-lime, tempered, and borosilicate.

Borosilicate glass is infused with boron trioxide which has a low thermal expansion. This means that, unlike normal glass, it won’t shatter when exposed to major temperature changes such as moving a dish from a fridge to an oven.

This is all thanks to the boron trioxide which makes glass resistant to temperature changes. Pyrex is a sub-group of borosilicate. Soda-lime glass is the most common type in kitchens as it is used for drinkware.

If the soda lime is untreated, it is more susceptible to breaking from extreme temperature changes. Tempered glass is the term used for soda-lime that has been heat-treated for durability.

What’s The Difference Between “PYREX” and “pyrex?” 

The two trademarks were used interchangeably in the past during the marketing of kitchenware products made of borosilicate and soda-lime glass. However, in recent times, Corning has licensed out the use of their PYREX (uppercase lettering) and pyrex (lowercase lettering) logos to other companies.

The lowercase pyrex is now mostly used for utensils sold in the US, South America, and Asia. PYREX is still available in Europe, Africa, and the Middle East.


Which Of Them Explodes?

In the past pyrex used to be made from borosilicate glass which does not break when exposed to major temperature changes. Pyrex eventually started using tempered glass because boron is a toxic substance and is very expensive to get rid of.

Still, even though tempered glass can withstand better thermal shock than regular glass, it is not as strong as borosilicate and this is what causes the shattering reaction people witnessed on TikTok.

If the logo on your utensil is lettered “PYREX”, it is most likely a product of borosilicate and thus safer. If it is lettered “pyrex" it is most likely made from soda-lime glass so be cautious if you’re doing any cooking over high heat.

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