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Fascinating....and typical....
I've known this for a long time. In related news: Pyrex isn't what it used to be.
Yeah, well, I just learned about the change. You're the first person I've run into that knew about it.
Pyrex - Sure as hell isn't....have any pyrex from your folks or Grans...? KEEP IT.
I have old Pyrex and new Pyrex, European glass ovenware, etc. and don't see any difference. Pyrex refers to a glass that has a near-zero coefficient of expansion with temperature.

What differences are you observing?
I mean, I didn't know any of the details. But I remember noticing that the product basically stopped working, some time around 1990, give or take half a decade. I theorized that the company was reacting to feedback that the plastic film was too sticky, and difficult to work with. Which it was; but the replacement didn't work at all.
Ah, yeah. I rarely used the stuff during the time it changed in 2004. I only started using plastic wrap a lot again in 2012. The adhesive-coated PE used in all consumer plastic wraps today is shit compared to original PVDC Saran Wrap and its knockoffs.

Since PVDC wrap is still made for certain commercial uses. now I'm looking to find a source for it.
What happened with a Pyrex casserole dish bought in 1995....bluntly, we had one of my Husband's meals shatter-plode in his hands. We were damned lucky - nothing was hurt, not us, nor our two fur-kinder. But there went dinner.
Hmm. Something went wrong, then. Making zero coefficient-of-expansion glass is not rocket science. I use modern glass bakeware all the time, several times a week, and have never had a problem. There shouldn't be a problem.

I don't know what happened in your husband's case. Flaws are always possible. Uneven cooling can be a problem. I mean, hitting a Pyrex dish at 400F with cold water will likely shatter it, but that's not what you did. I dunno. I'd see it as an unlucky occurrence.
So did Grimm. After that is when he started his Stainless Steel pot collection....
....also, Calphalon collection. Little to none glass, even Pyrex.

I managed to hang on to the Pyrex measuring cups.
in general I don't like using glass for most things anyway. any baking I might use Pyrex for, I use earthenware. the times when having a transparent cooking vessel is beneficial are few indeed.
Earthenware sounds interesting. Never used it.

Baking things in glass and baking them in an aluminum pan give very different results.

I imagine earthenware is a bit less heat conductive than glass. The fact that glass baking dishes are transparent has never been of used to me. I've never even paid attention to it. Lol.
Not everything I bake is in earthenware - mostly just casseroles and things like that. I'll also use an earthenware pan for roasting if I don't need my largest roasting pan, which is anodized aluminum. Cakes and pies and such, those I bake in metal. But that does remind me - I have some glass pie pans which I'll use from time to time because they're larger, but I don't think they produce as good results as metal. I do have an earthenware pie pan, but I pretty much never use it anymore except for fancy tarts, since it's "prettier" than my other options.
I suspected something had happened, I also remember the original Saran Wrap and have found the new wraps (and the Cling Wraps from Glad etc.) to be inferior to nearly useless.
@John Douglas Porter note that Pyrex is not what it used to be, they changed the formula and what they sell now is not as sturdy and should not be taken from freezer to oven directly as it will shatter, it has to be taken from fridge to room temperature slowly up to baking temps as again it can crack or shatter (though less violently than from freezer). The new stuff is no longer Thermal shock proof:

https://www.wideopencountry.com/pyrex-isnt-thermal-shock-proof-anymore-and-heres-what-you-need-to-know/

I have a number of the older Pyrex pieces that were passed down to me in the 1980s, before the 1998 changeover.
Fascinating. Thanks for posting this.

Given my original career path almost 60 years ago (Astronomy) I built two telescopes and learned about Pyrex, etc. It's not harder nor more expensive to make than ordinary glass, just different. So I can't imagine why it would be abandoned.
The best I've found (and I'm not saying it's the best out there) is Glad's Press-n-Seal. It works ok as long as the surface is dry and smooth. I think I've found that it can leave a tiny bit of sticky residue in some cases. Definitely not ideal. But it does a pretty good job of sealing, when it works.
Hmm. Learning that modern plastic wrap is coated with a moisture activated adhesive has been useful in the restaurant. I can now get it to stick to things like aluminum pots that it doesn't want to stick to by simply wetting my finger and wiping it on the surface just before wrapping it.

My quest now is to find sources for PVDC film. I'm sure the time saved will be worth any higher cost. This isn't so important in the home but in a busy restaurant every second, every extra motion counts.
It was driven by California's Prop 65 and general concern about chlorinated polymers. They didn't want to put that big cancer warning on their plastic wrap.

Also, my deep dive into plastic wrap and ways to come up with PVDC wrap we could use in the restaurant have come up with zero. I found one company that makes it in China but no means to buy from them. Today it's all PE or PVC with lots of plasticizer, and an adhesive coating. That's how press-and-seal works.
It’s not harder nor more expensive to make than ordinary glass
I'm curious what you're basing that on. I've read the opposite. Do you really think the change wasn't driven, ultimately, by economics?
Interesting… but my question was about glass. You said:
It [borosilicate glass] is not harder nor more expensive to make than ordinary glass
That’s not consistent with the information I’ve found.
I admit I'm going on memory. I could be mistaken. I don't have time to delve into it at the moment but I will -- working 12 hour back-to-back shifts feeding the hungry masses. Hah.
Oh, and tonight I tried to get that shitty plastic wrap to stick to a pot that's coated with non-stick inside and out. Hah. Good luck with that. No trick worked.

PVDC sure was nice. It also has a much higher temperature rating than polyethylene. You could stretch it over a glass dish and stick it in a 350 degree (but not higher) oven.