A Warning that Pyrex Glass Cookware Can Explode- Mostly Fiction!


Summary of eRumor:


The eRumor talks about what it describes as “exploding Pyrex.”  It says that the popular ovenware has been unsafe ever since the Corning Company sold the Pyrex brand to a company named World Kitchen.  It also claims that the product became inferior because it was now made of soda lime glass instead of borosilicate glass.  One final claim is that World Kitchen is not an American company.

The Truth:

We don’t know who the original author is of this email or his or her motives, but there is a lot said about Pyrex and the company that makes Pyrex that is incorrect.

Pyrex is one of the most widely used products in American households and has been used safely for decades.

According to World Kitchen, the makers of Pyrex, there has never been a recall of Pyrex or any concern about its safety on the part of the Consumer Product Safety Commission.

Like all glassware, Pyrex needs to be used according to instructions.  At the time of our investigation we found on the Pyrex website an advisory to consumers not to subject the product to extreme temperature changes, such as putting a Pyrex dish directly on a burner, under a broiler, adding liquid to a hot dish or placing a hot dish on a cold or wet surface.  Under those circumstances the glass can break.

The claim that the current makers of Pyrex abandoned borosilicate glass in favor or poorer quality soda lime glass is false.

World Kitchen told TruthOrFiction.com that Pyrex has been made from heat-strengthened soda lime glass for about 60 years and that the switch was first made by Corning, not World Kitchen.  The company added, “Consumers should know that soda lime glass, such as that used to make PYREX glass bakeware, is significantly more resistant to breaking on impact than borosilicate glass and comparably resistant to breakage caused by severe temperature changes.”

It is also false that World Kitchen is not a U.S. company.  It is an American firm and Pyrex is manufactured in the U.S.A..

Posted instructions from the Pyrex website


Any glass bakeware product can break if it is not used properly. For that reason, we want to remind consumers to review the PYREX® Safety and Usage Instructions provided with our products. While not a substitute for reviewing the entire Safety and Usage Instructions, set forth below are selected highlights.


NEVER use on top of the stove, under a broiler, in a toaster oven, or place over oven vent or pilot light. AVOID severe hot to cold temperature changes, including:

DO NOT add liquid to hot dish. DO NOT place hot dish or glass cover in sink. DO NOT immerse hot dish in water. DO NOT place hot dish on cold or wet surfaces. Handle hot ovenware and glass covers with dry potholder. ALWAYS add a small amount of liquid to the vessel prior to baking foods that release liquids while cooking. DO NOT overheat oil or butter in microwave. Use minimum amount of cooking time. DO NOT use or repair any item that is chipped, cracked or scratched.



To loosen baked-on-food, allow glass to cool, then soak. If scouring is necessary, use only plastic or nylon cleaning pads with nonabrasive cleansers.

WARNING: Failure to follow these instructions can cause immediate or later breakage which can result in personal injury or property damage.

Posted 10/20/09   Updated 11/21/13

A real example of the eRumor as it has appeared on the Internet:

About 5:30 PM there was a loud bang from the oven. Sylvia opened the oven door and the Pyrex dish had shattered into a million pieces. The roast beef (our first in many months) was peppered with small shards of very sharp glass. Normally,I am quick to inform Sylvia she did something stupid. However, this time she was nowhere near the stove when it blew. I shoveled the glass and the now mashed potatoes into a bucket with two putty knives. I then sucked the remains with the shop vac. I let everything cool down and then scrubbed the oven with Simple Green and some hot soapy water. It took over an hour to clean up the goo. Upon completion I ran the oven empty to see if the temperature controller was working okay. I suspected the oven got too hot and the dish simply blew. This was not the case however. The oven came up to temperature and cycled normally. We threw a disgusting frozen pizza in the oven and it cooked okay.

What is going on?

I Googled exploding Pyrex dishes and got ten million hits.
Exploding Pyrex is very common.

Here is the story.

A long, long time ago in a country we all know and love was a company named Corning. They made Pryex dishes. The material they used is called borosilicate glass. This stuff is indestructible. But like everything else, the Bottom Liners had a great idea: sell the technology to another company. The Chinese discovered that using soda lime glass was almost as good as borosilicate glass and a lot cheaper. Today, Wal-Mart is the largest distributor of Pryex products. Corning not only sold the technology to a company called World Kitchen, they also sold the rights to the original Pyrex logo. Seamless. The consumer will never know.

Now it seems people are getting hurt using soda lime Pyrex. We were lucky because the dish broke while the oven was closed and the damage was limited to the oven cavity. Others have been less fortunate. Some dishes explode when they are lifted from the heating rack in the oven with devastating results. Some people are heavily scarred. World Kitchen is in denial. They say that the dishes are another brand, not theirs. Contrary to their denials the victims usually have more than one of these dishes and the Pryex logo is clearly visible.

If you buy a Pryex dish beware. The label on the front says oven safe, freezer safe, microwave safe. The instructions on the back tell another story. You cannot move a soda lime Pyrex dish from the freezer to the oven and expect it to survive. The fine print goes on and on about what you are not allowed to do with the Pyrex dish. The fine print has prevented World Kitchen from being sued becaus e they have warned the consumer that their Pyrex dishes are junk from the get go. And they are the same price as the original Corning dishes. What a bunch of losers we all are for buying this crap.

What to do?

If you own borosilicate Pryex dishe s no fear. They have to be more than 25 years old to be sure they are indeed Corning dishes. I am not sure if the old Pryex dishes have anything stamped in them that indicates they are made by Corning. You may continue to use the soda lime dishes for holding stuff. Just do not attempt to roast or microwave with them as the hazard is very clear.

The reason the soda lime dishes let go is that over time they develop micro-cracks. Once a few micro-cracks are present and once some liquid finds its way into the cracks you have the bomb situation. The liquid is like shoving a crowbar in the dish and pulling it apart. Super heated liquids expand rapidly and it is the super heated liquids that force the soda lime glass to shatter into tens of thousands of shards.

Since Corning no longer makes Pyrex and Sylvia proudly holds a large collection of the soda lime Pyrex, we decided that one bomb in the kitchen is enough. The Pyrex dishes will go bye-bye in this week’s trash. I do not know what we will use for cake and pie dishes going forward . If you have some suggestions we are listening.

I strongly urge you not to use the soda lime Pyrex for the oven, stovetop or microwave. The slightest invisible crack is all it takes to have a mess and a possible injury.

As to World Kitchen: them and their cheap dishes. In case you are wondering: World Kitchen is not a USA company.