Some Questions About Pyrex

weinoo · December 31, 2014

This is interesting...

Older clear-glass Pyrex manufactured by Corning before 1998, Arc International's Pyrex products, and Pyrex laboratory glassware is made of borosilicate glass. According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 4.0% boron, 54.0% oxygen, 2.8% sodium, 1.1% aluminium, 37.7% silicon, and 0.3% potassium.[9][10]

According to glass supplier Pulles and Hannique, borosilicate Pyrex is made of Corning 7740 glass, and is equivalent in formulation to Schott Glass 8830 glass sold under the "Duran" brand name.[11] The composition of both Corning 7740 and Schott 8830 is given as 80.6% SiO2, 12.6% B2O3, 4.2% Na2O, 2.2% Al2O3, 0.04% Fe2O3, 0.1% CaO, 0.05% MgO, and 0.1% Cl.

Pyrex glass cookware manufactured by World Kitchen is made of tempered soda-lime glass instead of borosilicate.[12] World Kitchen justified this change by stating that soda-lime glass was cheaper to produce, is the most common form of glass used in bakeware in the US, and that it also had higher mechanical strength than borosilicate—making it more resistant to breakage when dropped, which it believed to be the most common cause of breakage in glass bakeware. Unlike borosilicate, it is not as heat resistant, leading to an increase in breakage from heat stress. European Pyrex is still made from borosillicate.[5][13][14]

WIKI.

sueveid · January 13, 2015

So if I look at a piece of Pyrex and it says USA, it is still the old formula?

Yes, if it says USA right on the piece itself.

The "pyrex", made of soda lime glass, by World Kitchens is not made in China. It is made in the US at the old Corning Charlerois, PA. Pyrex plant which they bought. It is all usually still marked in some form "USA" so this is not reliable. WK actually claims that Pyrex was made of soda lime glass since the 40s and it is true that some was made of soda lime glass. It was all the opaque, mostly white type and all made at the Charlerois plant. The clear colorless, borosilicate Pyrex was made in other plants. Evidently the plants are specific to the type of glass. The problem with the soda lime is that it will only tolerate about a 100F difference of temperature within the piece of glass. Borosilicate tolerates about 300F. Pyroceram, the old Corningware tolerates 8-900F difference within the piece. Corningware was also bought from Corning by World Kitchens and now is stoneware, made in China. They did in 2009 start manufacturing pyroceram again, in France but it is prohibitively expensive. It is easy to find the real stuff on the secondary market and often in pristine condition. There is also another Corningware, SimplyLite, vitrelle glass made in Corning NY but it may have been DC'd

There are some ways to tell the difference between the old and new Pyrex, but all you can do is reduce the risk of shattering not elininate it.

I would not use anything in the oven or with heat.-

--marked "pyrex". lowercase--This is the newer trademark and if you look at the http://www.pyrex.com/ website, the borosilicate glass is still trademarked "PYREX" and the soda lime is "pyrex". Clear colorless "PYREX" is most likely borosilicate. Some of the newer "pyrex" dishes have really big handles which cool more rapidly and increase the chance the dish will shatter.

--anything opaque. These are vintage and marked marked "PYREX" too and mostly are white. They are soda lime glass

--anything needle cut-I have a cute little pie pan but the needle cutting damages the integrity of the glass This would be on a vintage PYREX piece.

--anything with visible damage, nicks or cuts Glass can bruise and shatter without warning.

--avoid thicker pieces, with bluish or green coloring This is a little more subtle and there is a bluish clear early "PYREX" marked flameware that can be used on gas or electric elements with a trivet.

http://en.wikipedia.org/wiki/Pyrex#mediaviewer/File:Pyrex_and_PYREX.jpg

I decided to replace my PYREX with pyroceram where I could. There is Corningware,Arcoflam, Narumi, Pyrosil, Pyroflam and the old Visions line made of Calexium. The pyroceram is smooth on the bottom. The stoneware is thicker and has a bump round the edge. The stoneware says no stovetop or broiler. http://cookinwluv.blogspot.com/2011/07/blue-cornflower-corningware.html

I don't like pyroceram on the stovetop because it doesn't cook evenly but it is great for bakeware. The only problem is you can't see through it. Corning tried to address the poor heat conduction by making the "Rangetopper" line that has metal on the bottom.

Another Pyrex question: The instructions for my new Pyrex dish say to only put the dish in an oven preheated to the desired temperature. Why is that? For some items that I cook, the dish goes into a cold or cool oven and everything comes to temperature together. Seemingly, that's unacceptable for these dishes. Or is that unacceptable for any glass or ceramic dish?

I think this is to avoid the exposure of the heat from the element coming on for preheat.

Lisa Shock · August 6, 2017

Do an internet search for "exploding pyrex". I had a pyrex measuring cup explode in my hand while measuring cold water, nothing hot was involved, about a decade ago. I have gotten rid of almost all all the glass bakeware in my kitchen, just some Duralex custard cups remain, and almost all of the ceramics (just holding on to a couple of vintage items with sentimental value). Honestly, I use my copper clad stainless pots and pans, plus my beloved wok and cast iron, for almost everything and for baking I use professional sheet pans and hotel pans.

Edited August 7, 2017 by Lisa Shock
forgot to add cast iron (log)

Thanks for the Crepes · August 7, 2017

I think the exploding Pyrex is a problem with the later manufactured stuff after they switched from borosilicate glass to tempered soda lime glass. I have a bunch of pieces that I bought years ago and have never had a problem with them, but there is definitely a problem with the newer stuff, which you could not pay me to accept.

@Lisa Shock, was your measuring cup of recent manufacture? That is so scary, and I am seriously wondering how that could happen.

I've had several glazed stoneware pieces that are marked "oven proof" (they aren't) fail, but they usually just crack into two or three pieces, ruining your food, of course. I got rid of them because the oven proof part was most of the appeal.

A live in boyfriend had a set of Visions pots and pans. This was in the late 80's to early 90's. I liked them because you can see inside as to what's going on with the food. I can't recall an undue problem cleaning them and I do remember missing them when he moved out enough to invest in some cookware with tempered glass lids so I could see my food cooking again. We used the Visions on the stove top with no problem, but that was then and this is now. I would not even consider soda lime glass for kitchen ware, but if you can find the vintage borosilicate, you will be fine, I think.

Lisa Shock · August 7, 2017

The cup was purchased in 1997, right after a move. It exploded in 2007, in front of witnesses. It was in the cupboard, I pulled it out and was putting water from the tap into it and it just exploded. I did not knock it on the sink or anything.

I know about the 2 types of glass, and drink from Duralex cups. What worries me are baked goods and savory foods that people regularly cut into while still in the pan. I looked at my Pyrex pan from 1984, which had seen many a lasagna cut inside it, and realized that there was a huge network of scratches - any of which could cause failure. At least a SS hotel pan won't break because it got scratched.

Between the French oven that came with my copper-clad pans, my cast iron Dutch oven, and a variety of hotel pans, I realized that I have a lot of good options for baking the savory foods I generally bake like: baked beans, lasagna, macaroni casseroles, scalloped potatoes, enchiladas, etc. (I love making frittatas in cast iron skillets!) I do have dedicated pans (sheet pans, cake pans) for pastry, breads and other bakery items -once again, I don't really need anything glass or ceramic beyond the occasional custard or souffle cup.

I guess that I also realized that I simply owned a lot of pans, far beyond my stove's capacity, and I really did not need that many. I also realized that I had a lot of glass mixing bowls, but was limited with how I could use them -I was nervous about whipping cream or eggs. At the same time, I also own a good collection of steel bowls in various sizes (for several of them I have as many as 4 of the same size) and I realized I could easily just use the steel bowls if I purchased a couple more. The steel bowls stack nicely and don't weigh very much.

Nowadays, I don't worry about dropping pans when moving them around. And, I can grab bowls quickly and easily.

Thanks for the Crepes · August 7, 2017

9 minutes ago, Lisa Shock said:

The cup was purchased in 1997

That is not old enough, but still shocking that it could have happened with a cup at room temp from a cabinet! If I did not know and respect you so much, that would be hard to believe, but I do know, trust and respect you, so it happened. That soda lime glass cheat cost cut is horrible and no way to sue Chinese companies for injuries or losses. Brought to you by businessmen/women who poisoned their countrymen's babies with formula tainted with melamine. Some of the responsible parties were eventually executed, but that did not bring the babies back to life.

Here's a link to how the good and useful cookware became extremely dangerous.

I "love" 9_9 the statement that there has never been a recall on their products. They also rest on their laurels of past performance of decades, which is true, but things have changed and not for the better for the consumer. That is because the political climate here in USA and many other places is so friendly to business that even people who are severely injured by their lower than crap products nowadays have a hard time suing. Please don't buy soda lime glass. It is dangerous in your kitchen!

pastrygirl · August 7, 2017

7 hours ago, Thanks for the Crepes said:

That soda lime glass cheat cost cut is horrible and no way to sue Chinese companies for injuries or losses. Brought to you by businessmen/women who poisoned their countrymen's babies with formula tainted with melamine.

I don't think it is fair to blame (or try to sue) the factory if Pyrex changed the formula and the factory was delivering product made to Pyrex's specifications. If someone at the factory independently substituted a different/cheaper ingredient or process without consulting the parent company, that's a different story than if Pyrex simply decided to change the formula and the new formula sucks.

Toliver · August 7, 2017

This discussion has become a burr under my saddle, so to speak. Every where I go now on the internet, I am deluged with photos/ads of that horrible "Visions" cookware that I linked to in my earlier post.

Grrrr.

JoNorvelleWalker · August 7, 2017

9 hours ago, Thanks for the Crepes said:

That is not old enough, but still shocking that it could have happened with a cup at room temp from a cabinet! If I did not know and respect you so much, that would be hard to believe, but I do know, trust and respect you, so it happened. That soda lime glass cheat cost cut is horrible and no way to sue Chinese companies for injuries or losses. Brought to you by businessmen/women who poisoned their countrymen's babies with formula tainted with melamine. Some of the responsible parties were eventually executed, but that did not bring the babies back to life.

Here's a link to how the good and useful cookware became extremely dangerous.

I "love" the statement that there has never been a recall on their products. They also rest on their laurels of past performance of decades, which is true, but things have changed and not for the better for the consumer. That is because the political climate here in USA and many other places is so friendly to business that even people who are severely injured by their lower than crap products nowadays have a hard time suing. Please don't buy soda lime glass. It is dangerous in your kitchen!

Here is a picture from Wikipedia that illustrates the difference:

https://en.wikipedia.org/wiki/Pyrex#/media/File:Pyrex_and_PYREX.jpg

I believe all my measuring cups are borosilicate. My three newest say "Corning NY USA". My older ones no longer say much of anything at all.

**ElsieD** · August 7, 2017

1 hour ago, JoNorvelleWalker said:

Here is a picture from Wikipedia that illustrates the difference:

https://en.wikipedia.org/wiki/Pyrex#/media/File:Pyrex_and_PYREX.jpg

I believe all my measuring cups are borosilicate. My three newest say "Corning NY USA". My older ones no longer say much of anything at all.

So clear Pyrex good, blue Pyrex bad?

Porthos · August 7, 2017

Bold Block Letters logo: Good, rounded: lettering bad.

I have very littel glass in my kitchen; if I were single there would be even less.

lindag · August 8, 2017

I have a set of the blue cornflower Pyrex made for microwave use that I got for my first microwave in the mid 70s

I'm still using it and have only had to find a new lid for the little skillet (that I found on eBay).

I've actually I've used it on the stovetop but only under very low heat.

Edited August 8, 2017 by lindag (log)

JoNorvelleWalker · August 8, 2017

5 hours ago, ElsieD said:

So clear Pyrex good, blue Pyrex bad?

Apparently...and the French made Pyrex is said to still be borosilicate.

boilsover · August 8, 2017

On 8/2/2017 at 9:05 AM, Toliver said:

Corning makes a "Visions" line of cookware, but I can't recommend it for stove-top use.

My mom had this (click) sauce pan and tried using it to make something simple like gravy. It always, without fail, burned at the bottom.

Good luck with your search.

This is funny. Visions is THE worst cookware ever, IME. At IHHS last year, even the people making it admitted to me how atrocious it is.

To the OP: No cookware on the market is unsafe (at least from a poison-in-your-food standpoint). If you dine out, you are already regularly eating food cooked in bare aluminum. And you are getting dramatically more aluminum from your toothpastes and antiperspirants, among myriad other products.

boilsover · August 8, 2017

On 8/5/2017 at 9:36 PM, Lisa Shock said:

Do an internet search for "exploding pyrex". I had a pyrex measuring cup explode in my hand while measuring cold water, nothing hot was involved, about a decade ago. I have gotten rid of almost all all the glass bakeware in my kitchen, just some Duralex custard cups remain, and almost all of the ceramics (just holding on to a couple of vintage items with sentimental value). Honestly, I use my copper clad stainless pots and pans, plus my beloved wok and cast iron, for almost everything and for baking I use professional sheet pans and hotel pans.

I agree with you 100% about Pyrex (yes, all years, both borosilicate and soda lime glass) being an unreasonable safety risk. However, it is a different animal than pyroceram, from which Visions is made. IMO, Visions is much safer in terms of breakage, but words escape me to describe how horrible it is to cook in.

JoNorvelleWalker · August 8, 2017

40 minutes ago, boilsover said:

I agree with you 100% about Pyrex (yes, all years, both borosilicate and soda lime glass) being an unreasonable safety risk. However, it is a different animal than pyroceram, from which Visions is made. IMO, Visions is much safer in terms of breakage, but words escape me to describe how horrible it is to cook in.

I recently gave the last of my Visions away. Good riddance, horrible cookware. However Visions is not -- never to be confused with -- Pyroceram. Please.

boilsover · August 8, 2017

1 minute ago, JoNorvelleWalker said:

However Visions is not -- never to be confused with -- Pyroceram. Please.

Umm...unless you know more than the manufacturer does... "Why is Visions so light and clear and yet able to handle such extreme changes in temperature? Because it’s made of a revolutionary glass ceramic material called Pyroceram " See, http://www.worldkitchen.com/en/blog/blog-Visions-the-visions-story.html

Lisa Shock · August 8, 2017

4 hours ago, lindag said:

I have a set of the blue cornflower Pyrex made for microwave use that I got for my first microwave in the mid 70s

I'm still using it and have only had to find a new lid for the little skillet (that I found on eBay).

I've actually I've used it on the stovetop but only under very low heat.

I believe you are referring to CorningWare, not Pyrex. Pyrex is clear, CorningWare is white and often has patterns on it like the blue cornflower.

JoNorvelleWalker · August 8, 2017

45 minutes ago, boilsover said:

Umm...unless you know more than the manufacturer does... "Why is Visions so light and clear and yet able to handle such extreme changes in temperature? Because it’s made of a revolutionary glass ceramic material called Pyroceram " See, http://www.worldkitchen.com/en/blog/blog-Visions-the-visions-story.html

And they call soda-lime glass Pyrex.

lindag · August 8, 2017

8 hours ago, Lisa Shock said:

I believe you are referring to CorningWare, not Pyrex. Pyrex is clear, CorningWare is white and often has patterns on it like the blue cornflower.

Ah yes, you are correct....duh.

boilsover · August 8, 2017

8 hours ago, JoNorvelleWalker said:

And they call soda-lime glass Pyrex.

The full story of what is/has been called Pyrex is long and boring. Suffice it to say, at least in USA, Pyrex could always have been either soda lime or borosilicate--the US plants made both, although now all Pyrex under the World Kitchen license is soda lime. So if you're buying new in USA, it's soda lime, and it's still Pyrex. If you're buying vintage, you need some expertise to tell which it is. If you want borosilicate, you can buy the European manufacture. In both cases, it's a safety hazard, but soda lime more so.

Edited August 8, 2017 by boilsover (log)

Porthos · August 8, 2017

@boilsover I am having trouble finding any information about pre-1998 Pyrex that used soda lime glass. Do you have any links handy for me to peruse?

boilsover · August 9, 2017

6 hours ago, Porthos said:

@boilsover I am having trouble finding any information about pre-1998 Pyrex that used soda lime glass. Do you have any links handy for me to peruse?

Handy? No. But I believe it was discussed at length here: https://www.chowhound.com/post/consumer-reports-investigates-exploding-pyrex-751340

Corning had two plants, the epoymous one at Corning, and the other at Charleroi, PA. While the latter has been making Pyrex since the 1930s, the Corning plant is no longer in operation. It's my understanding that the Charleroi plant made both soda lime and borosilicate until the early 1990s, and which time it dropped borosilicate manufacture. This predates World Kitchens license of Pyrex from Corning in 1998. IIRC.

Here's a source, quoting Corning and WK people, that Charleroi has been making soda lime Pyrex for 60 years: http://www.snopes.com/food/warnings/pyrex.asp#BDYHoeyAKzyLdaaE.99

Edited August 9, 2017 by boilsover (log)

Porthos · August 9, 2017

@boilsover Thank you.

lindag · August 25, 2017

Reading though this thread made me think back to the set of Pyrex bowls in Mom's kitchen in the 50s.

Her signature dessert was made-from-scratch banana pudding put together in that big 'ol yellow bowl!

il_570xN.1239912950_3rzi.jpg

Edited August 25, 2017 by lindag (log)

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