Pyrex Revisited...

[mattl]

I recall there was a discussion on Pyrex here some years ago, came across this article today in Gizmodo

 

Interesting read, take a look.

 

One interesting tidbit near the end of the article is this:

 

<blockquote>
What does seem crystal clear on a scientific level is that borosilicate glass is less prone to thermal shock that soda lime glass. It’s also not hard to find, especially if you can live without the Pyrex logo being stamped on the bottom of your pan. Heck, Amazon Basics sells a pair of borosilicate glass pans for $15. The equivalent Pyrex-branded set made of tempered soda-lime glass costs $22. And according to experts, the Pyrex glass can explode into small pieces. Uncommon as these explosions may be, they sound bad.

 

</blockquote>
So I guess you can still get a good quality product today, it just wont say "Pyrex" on it....

 

 

The Pyrex Glass Controversy That Just Won't Die

Clear glass Pyrex cookware is practically an American icon. With its pleasing heft and remarkable resilience, these famous clear pans have been essential

gizmodo.com

 

[earthling177]

Well, there are multiple angles to look at this, and it's not cut and dry.

My own mother was a home ec teacher, and she always told us to never put pyrex on wet surfaces or even cold granite countertops, for example. This was during the 60's and 70's, when it was supposedly still made with borosilicate.

It's also true that things that are *still* made with borosilicate glass continue to explode even in situations where they shouldn't -- for example, Bodum Santos (now called Bodum Pebo) is a vacuum pot made out of borosilicate glass, and in the past few years they modified the instructions from "use a wire heat 'diffuser' if you use an electric coil burner" to telling people to use it also with a gas stove, and if you look at Amazon, there's a lot of people complaining about their vacuum pots exploding and the pictures show a gas stove.

It's also true that in Chemistry labs, sure, they often use a bunsen burner with test tubes directly (but with a very low flame), but when one is using a beaker or other large flasks, one usually uses a heat diffuser between the bunsen burner and the flask.

I do believe that tempered soda glass is way more likely to break than borosilicate or other heat-resistant glasses, but it still happens even with the proper glasses, because they are less resistant to mechanical shocks, so any nicks or scratches can weaken them to thermal shocks -- someone (Panthera, perhaps?) a few years ago described something along the lines of someone experienced a shattered Visions pot, for example.

One needs to be careful with such vessels.

 

[foraloysius]

I did a bit online shopping. So far I only found Pyrex products made of borosilicate glass available on this side of the big pond.

 

[combo52]

Pyrex Type Glass

I never heat anything in Pyrex type glass, in fact I hardly own any Pyrex, Why ? with stuff that can break so easily if heated or handled improperly when there is so much Corning-ware around, I probably have several hundred pieces if Corning-ware cook ware that I use in the ovens and microwaves and occasionally on the stove top.

 

John

 

[kate1]

I have had far too many pirex dishes shatter on me over the years. I always blamed myself for doing something wrong because they broke after being taken out of the oven, I thought I wasn’t letting them cool down slowly enough. I finally had one literally explode IN the oven and I was done. It was a deep dish blueberry pie and it was the biggest mess (and I think most expensive because that was a lot of fresh blueberries) I have ever had to clean up. Some of these dishes were vintage ones I inherited from my grandmother too so I don’t think borosilicate is actually that much superior, though I am certain it’s at least better than the soda lime because that’s what exploded inside my oven, the borosilicate ones only ever shattered outside of the oven.

 

[mattl]

I don't know.  I'm still using Pyrex that was my mother's, Odds are some of it is from the 40's and 50's.  Only thing that has ever broken was a Visions pot I really liked but I hit I just right with a mixing spoon or something.  I can tell my older pie plates as they are less greenish, or clearer is the best way to describe them.  I have some newer Anchor Hocking that have a definite green cast to them.  Really don't know what type of glass they are made from.

 

[kb0nes]

It all comes down to the coefficient of thermal expansion of the material. All glasses are equally "heat resisting" as they all melt at more or less the same temperature. It is when glass is exposed to gradients of temperature causing part of it to expand or contract that internal stresses build causing breakage. Don't set any piece of oven-hot glass on a wet washcloth or you risk breakage no matter what it is made of.

Borosilicate glass is QUITE different from other glasses as its coefficient of thermal expansion is 1/2 to 1/3 that of other common glasses. This is the reason that lab glassware can endure the thermal shock that it does. Note that lab glass is generally pretty thin which is an advantage when dealing with temperature extremes, thin glass probably won't hold up as well in a home environment though due to handling.

The fact that the word Pyrex appears on a piece of home kitchenware DOESN'T mean it is borosilicate! Even back when the Pyrex name was owned by Corning there were pieces that were still tempered Soda Lime glass. Now that it is a World Kitchens name the use of borosilicate at all is over.

As long as the heating is uniform and the piece isn't allowed to have serious temperature differential anywhere across the piece any glass will survive just fine. But for safe home kitchen use the choice of Corning Pyroceram is the wise choice, you won't hurt this material no matter what you do with it. Visions was mentioned also and this material is quite different from borosilicate glass also, it is far more comparable to corning pyroceram.

I'm with John on the Pyrex in general, measuring cups and a couple of mixing bowls are about the only Pyrex I own and I don't heat it any of it. Corning pyroceram is DIRT cheap in the thrift stores and a much better in the oven.

The following video is fun to watch. Note that while they call the piece they are using Pyrex, it isn't borosilicate