In recent days I’ve spent a lot of time browsing social media to pass the long hours at the hospital with a family member. In doing so, I came across a ‘pyrex bashing’ which in turn brought back an old memory. Some years ago, I had prepared a casserole dish ahead using a glass baking dish. When it was time to bake it for serving, I brought it out of the refrigerator and popped it into a cold oven. As the oven came to temperature, I heard a loud pop and cracking sound. Sure enough, the baking dish had cracked and split. This was a baking dish I had used for several years and probably had done the same with it many times. So what happened to my trusted “Pyrex” and why bash Pyrex?
I have no intention of bashing Pyrex or any other brand of glass kitchenware. Rather, I would advocate to be a conscious consumer, know what one has, and use it properly. Pyrex has been a trusted household name for decades and is often used as the word to refer to glass kitchenware and bakeware used for cooking and baking whether it is the Pyrex, Anchor Hocking, Bake King, or any other brand. Pyrex was valued for years for its sturdiness and ability to withstand rapid, dramatic temperature changes that typically shatter normal glassware. With changes in manufacturing, that old-fashioned reliability has changed.
Pyrex (trademarked as PYREX) is a brand introduced by Corning Inc in 1915 for a line of clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware. It was later expanded to include clear and opal ware products made of soda-lime glass. In 1998, Corning sold the Pyrex brand name to World Kitchen LLC. World Kitchen stopped the manufacture of borosilicate glass and changed to less expensive, tempered soda-lime glass for kitchenware sold in the United States. Tempered soda-lime glass does not handle heat as well as borosilicate glass but does withstand breakage when dropped better. With some caution, tempered soda-lime glass withstands thermal shocks reasonably well. (To be fair, Anchor Hocking and Bake King products are also made from tempered soda-lime glass.)
I have a mix of Pyrex glass kitchenware that has accumulated over the years and the one that cracked was newer. How can you tell whether you have a newer or older form of Pyrex? Here’s what to look for:
PYREX® (all UPPER CASE LETTERS plus, in the USA, a trademark notice comprising a capital R in a circle = low-thermal-expansion borosilicate glass either clear or opaque originally made by Corning Inc.
pyrex® (all lower case letters plus a trademark notice comprising a capital R in a circle) = clear tempered high-thermal-expansion soda-lime glass kitchenware made by World Kitchen.
PYREX (all UPPER CASE LETTERS in an encircled oval with no trademark notice with European country noted) = European license for use on borosilicate glass products manufactured by International Cookware.
So, in short, if glass kitchenware made from borosilicate glass is important to you, look for the trademark in ALL UPPERCASE LETTERS. You will need to scour estate auctions, thrift stores, antique stores, or purchase in Europe to acquire it. I’m glad that I still have some of the PYREX® pieces.
If you are resigned to using the modern-day tempered soda-lime kitchenware, some precautions are necessary. In 2010, Consumer Reports tested some Pyrex and found that taking the newer glass out of a hot oven and placing it on a wet granite countertop yielded poor results with the glass shattering almost instantly. As a result of its investigation, Consumer Reports called on the Consumer Products Safety Commission (CPSC) to look into the problem of shattering bakeware.
Further, Consumer Reports issued ten precautions to consumers to minimize the chances of the glassware shattering:
- Always place hot glassware on a dry, cloth potholder or towel.
- Never use glassware for stovetop cooking or under a broiler.
- Always allow the oven to fully preheat before placing the glassware in the oven.
- Always cover the bottom of the dish with liquid before cooking meat or vegetables.
- Don’t add liquid to hot glassware.
- If you’re using the dish in a microwave, do not use browning elements, and avoid overheating oil and butter.
- Do not take dishes directly from the freezer to the oven or vice versa.
- Never place hot glassware directly on a countertop (or smooth top), metal surface, on a damp towel, in the sink, or on a cold or wet surface.
- Inspect your dishes for chips, cracks, and scratches. Discard dishes with such damage.
- To avoid risks associated with glass dishes, consider using metal bakeware for conventional and convection ovens.
As always, it is the consumer’s responsibility to read and save the manufacturer’s instructions for handling the product safely and then follow through. If it’s too late for those instructions, check the label on the glassware for the designations given above to determine the glass content; and if it is an Anchor Hocking or Bake King product, know that it is a tempered soda-lime product. If in doubt, the precautions issued by Consumer Reports will suffice for all.
5 thoughts on “Glass Kitchenware Cautions”
Soba is traditional Japanese cuisine and Soba is a traditionally made with 100% buckwheat flour. Soba is like roughly as thick as spaghetti, and prepared in various hot and cold dishes.
“ PYREX® (all UPPER CASE LETTERS plus, in the USA, a trademark notice comprising a capital R in a circle = low-thermal-expansion borosilicate glass either clear or opaque originally made by Corning Inc.”
The opaque glass was never borosilicate. The old trademark, “PYREX” was used on clear bakeware that was made of borosilicate. These were produced in borosilicate plants. Corning also used It on opaque soda lime glass products that they started making when they purchased the soda lime glass factory in Charleroi, Pa in 1936. This is why World Kitchen can say Pyrex as a general term was made in both ways.
World Kitchen bought the Charleroi soda lime plant and the “pyrex” trademark and started making clear bakeware in that plant. Corning still uses the “PYREX” trademark on borosilicate labware.
For someone wanting the old borosilicate PYREX, they should avoid opaque PYREX.
Very informative article. Thanks for sharing the tips for preventing glass kitchenware cautions and buying guidelines for PYREX glass.