Unmitigated food disaster

[john south]

After preparing and partially boiling vegetables and meat, they were then put in a large glass bowl and it was placed on top of a gas hob to bring them to the boil. That was prior to placing it in the oven to make an oven casserole.

This practice has been done by me quite a few times before. I've always assumed that a Pyrex bowl can be placed on a gas ring and the contents boiled, because someone I know has Pyrex glass saucepans, that they use to boil things in.

However the wife doesn't think that these glass bowls should undergo this kind of treatment on top of the gas rings.

Today using a smoky dark coloured glass bowl which I don't think I've used before, but I really thought it was an oven proofed bowl. It suddenly completely collapsed into pieces as I placed it in the oven. What a mess.........

My question is not whether this was really an oven proofed glass dish, since i guess we will never know for sure.

But is the wife right in saying this is a very *risky* procedure, putting a pyrex glass bowl over a gas ring to boil things? Even though i always start on the minimum heat so as to minimize any strains on the glass. So would you think that this is safe to do, or not? Thanks.

[Andy Cap]

IANAE but apart from a specific glass saucepan, I 'wouldn't have dreamt of putting a Pyrex bowl directly on a gas hob. We regularly use ceramic ovenproof dishes, but again, I would not have considered putting them directly on the hob. Just my two-penneth FWIW.

[Julie Bove]

I'm with your wife on this one!

[Andrew Gabriel]

Pyrex doesn't imply a particular type of glass. Originally it was borosilicate glass, but it's now just used as a well-known trade name to sell various different types of glass. Different companies use the name differently in different parts of the world.

Borosilicate glass tends to be used for higher temperature applications, although I don't know what glass saucepans are made of.

Even soda-lime glass (used for most glass applications) shouldn't melt in an ordinary domestic oven. Sometimes it's toughened - did it break like a toughened windscreen shattering?

[Steve Firth]

Andrew Gabriel wrote: [snip]

Please don't feed the troll.

[MuddyMike]

Obviously not!

Mike

[Peter Parry]

[Bernard Peek]

Au contraire mon ami. We know about it's oven-proof status. What we don't know is whether it was designed to be so.

I wouldn't do it. The type of glass pan that can be put on direct heat is a comparatively new invention. Pyrex has existed a lot longer than that.

[BartC]

Even minimum heat involves a naked gas flame so would be very hot (try holding your finger over it!). And being more localised might result in even more stresses.

Trying using a microwave oven instead. Or a different vessel.

[Steve Firth]

borosilicate, not soda glass. And the "undetermined" claim that Corning swapped to soda glass in the 1990s is way out. Corning themselves changed to soda glass in the 1940s. Europe stayed with borosilicate because Corning licences production to J A Jobling who had some integrity.

[Adrian]

Steve Firth gurgled happily, sounding much like they were saying:

They did say that...

...the company's products now vended in the North American market are fashioned of tempered soda lime glass, a cheaper material. (The borosilicate glass version is still sold in Europe.)

They said that, too...

...the brand's current owner, World Kitchen, claims that changeover began back in the 1940s and long antedates Corning's 1998 sale of the brand: The Charleroi [Pennsylvania] plant has produced PYREX glass products out of a heat-strengthened (tempered) soda lime glass for about 60 years, first by our predecessor Corning Incorporated...

[therustyone]

Yellow glass pans (not ordinary pyrex) ere very common in the 90's and I still have a yellow glass frying pan in use. They are now retro items for collectors on eBay.

[Reentrant]

Maybe, but glass test-tubes and conical flasks have been used over Bunsen burners for a very long time.

[Man at B&Q]

[Man at B&Q]

Your point being....?

[Tim Streater]

Relatively thin glass though. And I don't think you heat them up empty. Or do you? - I heated a mixture of flowers of sulphur and potassium permanganate in a test tube once on a little burner at home. Nothing much happened for a while, then there was a "thunk" and all the mixture shot out as a plug, through the window I'd left open just in case.

[Lino expert]

Sorry to go off topic, and not wanting to hijack the thread, but why did you do it? Was it to try to cut down on the time it would be in the oven?

[Michael Chare]

You should get an induction hob. They are idiot proof in that respect!

As students we learnt that pinching half pint jugs from the bar to make coffee in was a waste of time. Though I recall someone having one that did last for some time.

[Andy Dingley]

I almost tagged that with [[WP:AGF]] and I don't share the "troll" sentiment at all.

However AFAIK, Pyrex is borosilicate and should resist most attempts at domestic heating, anything else that doesn't have specific labels is assumed to be soda-lime and I wouldn't even think about heating it.

[The Natural Philosopher]

The key is the expansion rate. If one part is much hotter than another, as can happen with gas when the bit with water in stays at 100C but eh bit above water goes higher, thermal expansion can crack the top off in a neat ring.

Pyrex is a low thermal coefficient of expansion glass. That's all.

So you can pour boiling water into it and it wont crack.