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.

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.

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).

In Germany borosilicate glass is called colloquially "Jenaer Glass" named after the city of Jena.

https://en.m.wikipedia.org/wiki/Jena_glass

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.

“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.

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

The article is written like a low-grade blog spam, and yet it is corning.com.

They reference events out of order, etc.

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

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?

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.

What a bunch of borons

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.

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.....