A Pyrex liquid measuring cup was one of the things I bought when I stocked my very first kitchen way back when. It stayed with me through my 20s and 30s—college, new jobs, cross-country moves, marriage, and beyond. Only last year did I finally replace it when the red measured markings had faded so much that they were no longer legible.
The Pyrex glass measuring cup is a staple in my kitchen, as it is for so many cooks. Beyond that, I use Pyrex casserole dishes, loaf pans, and pie pans often. I never paid much attention to the Pyrex logo, though, until I had to replace that measuring cup. While shopping around, I learned that there is a difference between PYREX with capital letters, pyrex with lowercase letters, and Pyrex with the capital “p.” I was as surprised as you might be—here are the differences.
Corning invented the brand Pyrex in 1915 and made all Pyrex products with borosilicate glass. This type of glass has an element called boron trioxide in it, which makes it highly resistant to major temperature changes, reducing the risk of it breaking.
Historically, Corning owned the trademark to the PYREX and pyrex logos and they were used interchangeably on all Pyrex branded products. Corning later licensed the use of the names PYREX and pyrex to two different companies who now produce the glass cookware.
You’ll now find cooking products labeled PYREX in Europe, Africa, and the Middle East, where they are still made with borosilicate glass. The label pyrex stayed stateside, and in the rest of North America, South America, and Asia, and the company that makes them no longer uses borosilicate glass. Instead, they are made with tempered soda-lime glass, which is heated and cooled in a manner that makes it more durable than regular glass under temperature fluctuations. While it’s still heat-resistant, it’s not quite as heat-resistant as borosilicate glass.
PYREX vs. pyrex: Which Is Safer?
Since PYREX is made with borosilicate glass, it is more heat-resistant and therefore less prone to breaking due to any sudden changes of temperature such as transferring a casserole from the refrigerator directly to the oven. That makes PYREX cookware safer than pyrex cookware, which runs a higher risk of exploding due to thermal shock—when the glass goes through an extreme temperature change that can cause it to fracture.
It's important to note that neither are 100% resistant to thermal shock.
How To Use Pyrex Cookware Safely
No matter if you own PYREX or pyrex cookware, it's important to care for them properly so that they don’t break. Follow these easy guidelines and Pyrex will be a long-lasting and safe staple in your kitchen for years to come.
Always avoid sudden drastic changes in temperature. Don’t pour boiling liquid into it. Let it cool down after pulling it from the oven before running cold water over it in the kitchen sink. Don’t put frozen or refrigerated casseroles or pies straight from the freezer into a hot oven and don’t put your cookware directly under the broiler. Also, store the baking dishes carefully to prevent microcracks in the glass, which can weaken them.
Pyrex: Brand name for cookware brand. pyrex: Lowercase indication of containers that should not be heated in the oven or microwave. These are most likely made of soda-lime glass. PYREX: Uppercase label on cookware that is made of borosilicate glass and can be heated in a microwave or oven.
The differences between Pyrex-branded glass products has also led to controversy regarding safety issues—in 2008, the U.S. Consumer Product Safety Commission reported it had received 66 complaints by users reporting that their Pyrex glassware had shattered over the prior ten years yet concluded that Pyrex glass ...
If the logo is in upper case lettering, PYREX, it's most likely made of borosilicate, and thus safer. The lowercase lettering is most likely made of soda-lime glass, so take extra care after any high-heat cooking.
To What temperature Is Pyrex Oven-Safe? Pyrex is oven-safe up to 425 degrees. However, direct contact with heating elements can cause the glass to shatter or break. Pyrex is not oven-safe when used under the broiler or in a toaster oven.
Glass is an inert material; it won't leach anything into food. Pyrex is basically a type of glass, and also hasn't ever been called out for any potential health problems. It's convenient for going from the oven to the fridge, but again, you can't really do much on the stovetop with it.
So, why did Pyrex make the change all those years ago? Two primary causes: increased air pollution regulations and a focus on reducing energy consumption. Soda lime glass is better for the environment, requires less energy to produce, and is more easily recyclable—making it the preferable choice.
Look for bakeware made from materials known for their non-toxic properties. Stainless steel, for example, is a durable and safe choice. Unlike nickel, it doesn't release harmful chemicals when heated, ensuring your baked goods stay pure. Also, pure ceramic bakeware and enameled cast iron are excellent options.
While Pyrex ovenware is a type of glass, it has been specially treated in the manufacturing process to withstand high temperatures, which makes it non-recyclable. Broken or chipped Pyrex should be disposed of carefully in the waste bin.
Ultimately, vintage Pyrex, made from borosilicate glass, is generally considered safe to use in the oven. Its robust composition makes it highly resistant to temperature changes and less prone to shattering, even when subjected to the high temperatures of an oven.
Pyrex itself does not contain lead, but the paint on older pieces often does. The amounts are small and it would basically be impossible to get “lead poisioning” from drinking from the item.
Because borosilicate is the most durable when it comes to withstanding temperature changes, it is generally considered the safest choice for glass bakeware.
Pyrex used to be made out of borosilicate, but now it's made of soda lime glass. Soda lime is less tough than borosilicate, although it is tough on impact. (But I think we all know not to hit glass superhard.) Borosilicate is what they use in laboratory glass and is tougher under any sudden temperature changes.
Knowing how to tell if Pyrex is vintage is an important skill. Start by looking for the Pyrex identification mark or logo. If it's all caps (PYREX), you likely have a vintage piece on your hands Then look at the pattern and shape to see if they match up with designs from decades past.
So What's the Difference? The short answer is: not that much! Both brands can go into the oven up to 425 degrees F (200 degrees C), recommend using trivets when moving from hot to cool surfaces, and come in a variety of shapes and sizes at affordable prices. It really just depends on which one you like more.
When did Pyrex change to soda-lime glass? Corning sold the Pyrex brand to World Kitchen in 1998, and they made the decision to switch from borosilicate to soda lime glass - but only in the United States. Pyrex brand made in other countries is still made of borosilicate.
Unfortunately when Corning, Inc. sold off the PYREX® trademark it became pyrex® in America and the new company started using Soda-Lime Glass instead of Borosilicate Glass. The company that bought the PYREX® trademark for European use continues to make Borosilicate Glass PYREX.
If it's all caps “PYREX,” it's vintage, made of borosilicate.If it's lower case “pyrex,” it's new, and it's soda lime. (In Europe, Pyrex is still made of borosilicate. So these recommendations only apply to Pyrex in the United States.)
When did Pyrex change to soda-lime glass? Corning sold the Pyrex brand to World Kitchen in 1998, and they made the decision to switch from borosilicate to soda lime glass - but only in the United States. Pyrex brand made in other countries is still made of borosilicate.
The brand switched its formula in the 1950s to the soda lime glass, but recently started reintroducing borosilicate glass. Although both glasses are heat-resistant, borosilicate glass does better with extreme temperatures, making the vintage Pyrex pieces highly coveted by collectors.
Introduction: My name is Geoffrey Lueilwitz, I am a zealous, encouraging, sparkling, enchanting, graceful, faithful, nice person who loves writing and wants to share my knowledge and understanding with you.
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