I used to worry about this but there's not a meaningful difference if you have any care for the tools and basic precautions. Borosilicate glass also tends to be more dangerous when it breaks. I've broken far more pieces of glassware due to mechanical reasons than thermal reasons.
Pyrex doesn't have a maximum temperature limit in a kitchen environment if you are careful. Preheating the oven is the #1 way to prevent issues. If you put a piece of glassware in an electric oven without preheating it, you can create massive temperature deltas between top/bottom. I can get an iron skillet beyond 700F in my electric oven if I leave it in there while it's preheating for a set point of just 450F. If the heating element has direct line-of-sight to the cookware, you always need to be wary of radiative heating effects.
Preheating the oven can also increase the risk of thermal shock shattering the glass. The maximum tolerated temperature change for soda-lime glass is only ~60C.
Not being able to put it under a broiler is a huge disadvantage for nicely finishing dishes like a lasagna.
Wow, I had never even considered that the pre-heating phase could potentially get things hotter than the normal cycling, but yeah that makes sense. It’s just broiling from another direction.
I think my oven might cycle the bottom element even when pre-heating, possibly to prevent this.
That's because a French company now owned by a US Private Equity firm, Arc International Cookware, owns the license for Europe, and as they have some pride, continue to make it with borosilicate.
It's available in the US under the "Arcuisine" brand.
I watched a video recently that dove deep into this as well[1]. It turns out there's not an easy way to figure out if it's borosilicate other than if it has "made in France" on it or if you know it was purchased in Europe. AFAICT, you can't really buy borosilicate Pyrex in the US.
The video does also show off a cool "mineral oil test" to tell the difference, but probably is only effective if you had something to compare it against.
My takeaway though was that I need to thrift some Corningware, though!
It's a non destructive test. Quote from the video (with funny youtube transcription spelling errors):
"Without getting too technical, the gist is if you put the mineral oil in a vessel made of boroilic and then dip another glass made of boroilicate into it, that glass will seem to disappear while others will not. So I filled a vintage what I think is made of borosilicate Pyrex vessel with mineral oil. Then it dipped in a vintage what I think is made of boro silicut loaf pan and it seemed to disappear right before my eyes. Eureka I thought the experiment works well until I dipped a new Pyrex piece lowercase that I know is not made of borocyic and it disappeared too. Once again, another spokesman at the Cording Museum of Glass that I reached out to said that even the mineral test isn't a sure thing. According to Brady Spalling, he says in order for glass to quote unquote disappear in oil, the glass being submerged must have a similar refractory index, which allows light to pass through both without significantly bending. Mineral oil and borosyic do have similar refractory indexes. So what you've heard is correct. This method is often used to quickly ascertain whether a glass object is borosyicate.
However, variability of glass recipes makes it difficult to rely solely upon this method. In short, it may work and it may not."
Relevant video from Ann Reardon's How To Cook That about exploding Pyrex (and the difference between all capitals and all lowercase): https://www.youtube.com/watch?v=YVbkDAw4aJs
Turned out that distinction isn't too reliable when it comes to determining whether a product used soda lime glass or borosilicate glass instead.
So there are three : PYREX borosilicate glass lab equipment, pyrex soda-lime glass cookware, and Pyrex borosilicate glass cookware made in France. Another childhood illusion shattered.....
If you're curious the only brand I could find easily purchasable in the USA that uses borosilicate glass is oxo. Their are some other results if you do a search on amazon, but I'm not very convinced those are really borosilicate glass.
You can relatively easily check this before buying, just look for the tint (usually best seen on the edges of the glass). Blueish = borosilicate, greenish = soda lime.
I remember when I was doing A-level chemistry at school circa 1970 we were told always to check that any glassware we were heating up a lot (or might be very exothermic) had the PYREX symbol on it, otherwise bad things could happen. A bit later, almost everything was PYREX.
> when I was doing A-level chemistry at school circa 1970 we were told always to check that any glassware we were heating up a lot (or might be very exothermic) had the PYREX symbol on it, otherwise bad things could happen
Speaking of "very exothermic" ... decades ago a lab colleague of mine once entirely blew out both (glass) sides of his fume cupboard while attempting to melt "ice" with a heat gun. Of course the "ice" that had formed in his flask during the previous reaction turned out not to be ice. The flask itself was later found in lots of very very tiny pieces.
It was the loudest bang I've ever heard, happily he sustained only very minor injuries, with hindsight a minor miracle.
He references this FAQ from the Corning Museum of Glass (CMOG):
> The short answer is that the change from upper to lower case signified a re-branding of the trademark Pyrex® in the late 1970s but is not a conclusive way to determine, historically, what type of glass formulation the product is made from.
Has anyone written a better explainer about the difference? Corning's entry isn't that helpful. Particularly interested in the safety issues and practicality in terms of kitchen use.
Also, I'm told that IKEA's "MIXTUR" line of glassware is more Pyrex-like than actual Pyrex. Is that true?
Pyrex was the brand for Corning's borosilicate glass products, which is an almost all-around superior substitute for regular soda-lime glass. Better acid resistance, lower thermal expansion, higher softening/melting temperature, etc.
Some marketing geniuses somewhere concluded that consumers wouldn't notice, and created the line of products that carry the confusing "pyrex" branding but aren't borosilicate based but just thicker or something.
And now they have to have this page to explain the differences.
It's some evil genius market segmentation on behalf of Pyrex management.
This sort of thing subverts the usefulness of trademarks. You buy from a traditionally upright company, but they just bait-and-switch you on the strength of their trademark and you might as well have bought any product labelled as pyrex.
This is why I like the concept of an "origin mark" that links to a full record of the whole supply chain for the product. Companies already have that information, exposing it makes buyers able to make [more] rational decisions and then capitalism can actually work to improve products.
That said, using the same trademark for different products in this way should invalidate the trademark (maybe UK TMA1994 S3 can be used in this way??).
I refuse to enter into joinder with this discussion, but for the record:
The all-caps name, PYREX, is the de jure, natural bakeware, created of the land (borosilicate). It has inherent, unalienable rights to withstand thermal shock. It is a true vessel.
The lowercase name, Pyrex, is the corporate fiction, the STRAWMAN created under the maritime law of commerce. It is a mere vessel in name only, subject to the whims and defects of its corporate creators. By purchasing it, you are unknowingly consenting to be governed by their rules of catastrophic failure.
Do not be deceived by their fraudulent conveyance. I do not consent to being a party to this contract. I am a free man, traveling upon the land with my original, common-law PYREX.
“World Kitchen in 2000, recognized that the cookware didn't need to be quite as strong, and — to make it accessible to the average customer — it needed to be more affordable.”
Some pretty strong bullshit vibes from this section. Feels a lot more like they decided to make the product worse because they knew the brand name would be enough. I doubt price is a significant factor compared to durability for the average home cook.
There are a few other downsides to borosilicate vs soda lime in a home kitchen (I still have euro and vintage only); if borosilicate breaks it is somewhat more dangerous.
Funny to me because just last week I week I wanted to buy a glass jug, and as a natural born procrastinator I just had to google products from Pyrex. Apparently the European products are still made of borosilicate glass in France. In the end I bought one from Anchor Hocking because it has markings etched in and a few people complain their Pyrex markings disappear. I did buy some dishes from Pyrex and they say borosilicate glass on the packaging (made in France).
I have a 25 year-old European glass bowl. PYREX is etched quite subtly on the underside. I bought another one about five years ago. The word PYREX now appears in relief inside the bowl. So a spoon catches on it. It is more readable but less usable. I won't be buying any more.
I used to worry about this but there's not a meaningful difference if you have any care for the tools and basic precautions. Borosilicate glass also tends to be more dangerous when it breaks. I've broken far more pieces of glassware due to mechanical reasons than thermal reasons.
Pyrex doesn't have a maximum temperature limit in a kitchen environment if you are careful. Preheating the oven is the #1 way to prevent issues. If you put a piece of glassware in an electric oven without preheating it, you can create massive temperature deltas between top/bottom. I can get an iron skillet beyond 700F in my electric oven if I leave it in there while it's preheating for a set point of just 450F. If the heating element has direct line-of-sight to the cookware, you always need to be wary of radiative heating effects.
Preheating the oven can also increase the risk of thermal shock shattering the glass. The maximum tolerated temperature change for soda-lime glass is only ~60C.
Not being able to put it under a broiler is a huge disadvantage for nicely finishing dishes like a lasagna.
I have had this happen. Mac and cheese into the preheated oven, boom. Glass shards all over the dishes on the lower rack. Almost ruined Thanksgiving.
Wow, I had never even considered that the pre-heating phase could potentially get things hotter than the normal cycling, but yeah that makes sense. It’s just broiling from another direction.
I think my oven might cycle the bottom element even when pre-heating, possibly to prevent this.
Just a note: The second “Pyrex” in the title should be all lowercase (“pyrex”).
Since the article is discussing the branding, this is relevant, as they use “Pyrex” in the article, to refer to “PYREX.”
In the UK PYREX cookware is always borosilicate. So it was a bit confusing to hear americans say how shit their "pyrex" glassware is.
Mind you, most of our oven proof glass is decent enough to be put in the oven and then dumped on a cold surface.
That's because a French company now owned by a US Private Equity firm, Arc International Cookware, owns the license for Europe, and as they have some pride, continue to make it with borosilicate.
It's available in the US under the "Arcuisine" brand.
I wonder if exploding cookware would get a British safety kitemark ?
More like a military rating.
Bake toward Enemy.
If you're interested in learning more about zero-expansion materials, Huygens Optics has a great video series on youtube: https://www.youtube.com/watch?v=qi8jmEbWsxU
I watched a video recently that dove deep into this as well[1]. It turns out there's not an easy way to figure out if it's borosilicate other than if it has "made in France" on it or if you know it was purchased in Europe. AFAICT, you can't really buy borosilicate Pyrex in the US.
The video does also show off a cool "mineral oil test" to tell the difference, but probably is only effective if you had something to compare it against.
My takeaway though was that I need to thrift some Corningware, though!
1: https://youtube.com/watch?v=2DKasz4xFC0
Mineral oil test bookmark: https://youtu.be/2DKasz4xFC0?feature=shared&t=873
It's a non destructive test. Quote from the video (with funny youtube transcription spelling errors):
"Without getting too technical, the gist is if you put the mineral oil in a vessel made of boroilic and then dip another glass made of boroilicate into it, that glass will seem to disappear while others will not. So I filled a vintage what I think is made of borosilicate Pyrex vessel with mineral oil. Then it dipped in a vintage what I think is made of boro silicut loaf pan and it seemed to disappear right before my eyes. Eureka I thought the experiment works well until I dipped a new Pyrex piece lowercase that I know is not made of borocyic and it disappeared too. Once again, another spokesman at the Cording Museum of Glass that I reached out to said that even the mineral test isn't a sure thing. According to Brady Spalling, he says in order for glass to quote unquote disappear in oil, the glass being submerged must have a similar refractory index, which allows light to pass through both without significantly bending. Mineral oil and borosyic do have similar refractory indexes. So what you've heard is correct. This method is often used to quickly ascertain whether a glass object is borosyicate. However, variability of glass recipes makes it difficult to rely solely upon this method. In short, it may work and it may not."
Soda-lime glass has a greenish hue (look at it sideways). Borosilicate is blueish.
Relevant video from Ann Reardon's How To Cook That about exploding Pyrex (and the difference between all capitals and all lowercase): https://www.youtube.com/watch?v=YVbkDAw4aJs
Turned out that distinction isn't too reliable when it comes to determining whether a product used soda lime glass or borosilicate glass instead.
So there are three : PYREX borosilicate glass lab equipment, pyrex soda-lime glass cookware, and Pyrex borosilicate glass cookware made in France. Another childhood illusion shattered.....
If you're curious the only brand I could find easily purchasable in the USA that uses borosilicate glass is oxo. Their are some other results if you do a search on amazon, but I'm not very convinced those are really borosilicate glass.
If you want borosilicate Pyrex, go to church bazaars and yard sales. The old stuff is better anyway.
pretty sure marinex is borosilicate too
You can relatively easily check this before buying, just look for the tint (usually best seen on the edges of the glass). Blueish = borosilicate, greenish = soda lime.
Don’t forget glowing green for uranium.
https://en.m.wikipedia.org/wiki/Uranium_glass
In Germany borosilicate glass is called colloquially "Jenaer Glass" named after the city of Jena.
https://en.m.wikipedia.org/wiki/Jena_glass
Probably because Schott glassworks was originally established in Jena as a sister company to Carl Zeiss.
Same in Romania, we probably got the name from you. We just call it "iena".
I remember when I was doing A-level chemistry at school circa 1970 we were told always to check that any glassware we were heating up a lot (or might be very exothermic) had the PYREX symbol on it, otherwise bad things could happen. A bit later, almost everything was PYREX.
> when I was doing A-level chemistry at school circa 1970 we were told always to check that any glassware we were heating up a lot (or might be very exothermic) had the PYREX symbol on it, otherwise bad things could happen
Speaking of "very exothermic" ... decades ago a lab colleague of mine once entirely blew out both (glass) sides of his fume cupboard while attempting to melt "ice" with a heat gun. Of course the "ice" that had formed in his flask during the previous reaction turned out not to be ice. The flask itself was later found in lots of very very tiny pieces.
It was the loudest bang I've ever heard, happily he sustained only very minor injuries, with hindsight a minor miracle.
There should really be a reality show about chemists.
There is loads of stuff on utube featuring idiots blowing things (and themselves) up with highly unstable compounds.
A recent video from the I Want To Cook channel on the topic:
* https://www.youtube.com/watch?v=2DKasz4xFC0
He references this FAQ from the Corning Museum of Glass (CMOG):
> The short answer is that the change from upper to lower case signified a re-branding of the trademark Pyrex® in the late 1970s but is not a conclusive way to determine, historically, what type of glass formulation the product is made from.
* https://libanswers.cmog.org/faq/398431
Has anyone written a better explainer about the difference? Corning's entry isn't that helpful. Particularly interested in the safety issues and practicality in terms of kitchen use.
Also, I'm told that IKEA's "MIXTUR" line of glassware is more Pyrex-like than actual Pyrex. Is that true?
Pyrex was the brand for Corning's borosilicate glass products, which is an almost all-around superior substitute for regular soda-lime glass. Better acid resistance, lower thermal expansion, higher softening/melting temperature, etc.
Some marketing geniuses somewhere concluded that consumers wouldn't notice, and created the line of products that carry the confusing "pyrex" branding but aren't borosilicate based but just thicker or something.
And now they have to have this page to explain the differences.
It’s borosilicate which is the original Pyrex.
The article is written like a low-grade blog spam, and yet it is corning.com.
They reference events out of order, etc.
And, when it’s supposed to be all about PYREX versus pyrex, they immediately start talking about Pyrex.
The article is atrocious.
It's some evil genius market segmentation on behalf of Pyrex management.
This sort of thing subverts the usefulness of trademarks. You buy from a traditionally upright company, but they just bait-and-switch you on the strength of their trademark and you might as well have bought any product labelled as pyrex.
This is why I like the concept of an "origin mark" that links to a full record of the whole supply chain for the product. Companies already have that information, exposing it makes buyers able to make [more] rational decisions and then capitalism can actually work to improve products.
That said, using the same trademark for different products in this way should invalidate the trademark (maybe UK TMA1994 S3 can be used in this way??).
What a bunch of borons
Okay... PYREX is borosilicate, pyrex is soda-glass. What about Pyrex? (Where only the first letter is capitalized.)
I won't lie. This is shitty marketing.
Im kind of sure making difference between "PYREX" and "pyrex" is illegal here.
Are these new python package managers?
I read the title and thought it was about C++ iterop.
Seeing the title I thought about the python type-checker Pyre
Don't give them any ideas.
I refuse to enter into joinder with this discussion, but for the record:
The all-caps name, PYREX, is the de jure, natural bakeware, created of the land (borosilicate). It has inherent, unalienable rights to withstand thermal shock. It is a true vessel.
The lowercase name, Pyrex, is the corporate fiction, the STRAWMAN created under the maritime law of commerce. It is a mere vessel in name only, subject to the whims and defects of its corporate creators. By purchasing it, you are unknowingly consenting to be governed by their rules of catastrophic failure.
Do not be deceived by their fraudulent conveyance. I do not consent to being a party to this contract. I am a free man, traveling upon the land with my original, common-law PYREX.
TYRANNOSAURUS PYREX will always win over lierex.
“World Kitchen in 2000, recognized that the cookware didn't need to be quite as strong, and — to make it accessible to the average customer — it needed to be more affordable.”
Some pretty strong bullshit vibes from this section. Feels a lot more like they decided to make the product worse because they knew the brand name would be enough. I doubt price is a significant factor compared to durability for the average home cook.
There are a few other downsides to borosilicate vs soda lime in a home kitchen (I still have euro and vintage only); if borosilicate breaks it is somewhat more dangerous.
Funny to me because just last week I week I wanted to buy a glass jug, and as a natural born procrastinator I just had to google products from Pyrex. Apparently the European products are still made of borosilicate glass in France. In the end I bought one from Anchor Hocking because it has markings etched in and a few people complain their Pyrex markings disappear. I did buy some dishes from Pyrex and they say borosilicate glass on the packaging (made in France).
I have a 25 year-old European glass bowl. PYREX is etched quite subtly on the underside. I bought another one about five years ago. The word PYREX now appears in relief inside the bowl. So a spoon catches on it. It is more readable but less usable. I won't be buying any more.
Essentially PYREX got enshittified into pyrex.