Some Questions About Pyrex

[thock]

The problem with tempered glass, versus untempered borosilicate glass, is that it relies on heat treatment to temper it. From the reports of "exploding" glass, or catastrophic failure (in more ways than one), it seems the majority of cases (if not all) are of tempered glass that has failed in some way. This is leading many to wonder whether the heating and cooling cycles that these items have undergone may serve to de-temper the glass.

I looked at your link, however, and it looks like most of Duralex's products are meant to be eaten or drunk from, and not cooked with or used as a casserole. I wouldn't be afraid to use tempered glass as dinnerware, and in fact, I do use Corelle. I just prefer not to use tempered glass (if I can help it) in the oven.

Tracy

[Lisa Shock]

Agreed. I use the Duralex to drink from, not cook.

I have been phasing out all glass cookware from my kitchen and replacing it with various metal pans. I've come to the conclusion that if cooking in metal pans is good enough at school/work it should be good enough for my house. I have a few legacy corningware items and some ceramic ramekins that I am using with caution, but, that's it.

[dcarch]

Tempered glass is extremely durable, and unlikely to self-destruct.

All modern high-rise building curtain walls are clad in tempered glass. Trillions and trillions of acres of glass, subjected to heat, cold, wind ----. You seldom hear about glass shattering in a building.

Glass, being technically a liquid, heating in an oven can eventually de-temper or create uneven internal stresses.

dcarch

[pep.]

All modern high-rise building curtain walls are clad in tempered glass. Trillions and trillions of acres of glass, subjected to heat, cold, wind ----. You seldom hear about glass shattering in a building.

Subject to heat, yes, but not to oven temperatures.

[Shel_B]

I was gifted with a 9 x 13 Pyrex brand baking dish and I noticed that the glass on the bottom of the dish is slightly wavy and subtly undulating, and has some streaks running through it, not at all smooth like the older Pyrex dishes.  Might these imperfections cause problems, such as cracking or breakage?  I'm glad I didn't have to pay for this treasure ....

Edited December 29, 2014 by Shel_B (log)

[JoNorvelleWalker]

As I understand it, recent pyrex really isn't pyrex.  That is to say not borosilicate.  Nor for that matter is corning ware any longer pyroceram.  What is sold now is junk.  Treasure your antiques.  Corning, for culinary purposes, is on the dung heap of history.

 

Disclaimer:  I cooked my dinner tonight in pyroceram.

[Shel_B]

My understanding is the same as yours, likewise for Corningware.  I do so love my Corningware and older Pyrex.  If anything happened to those dishes I'd be very sad.

 

However, the question remains: will the imperfections in the new Pyrex dish contribute to problems of cracking, breakage, or ... ?

[Smithy]

The streaks are a surprise. Care to post a photo? I think the waviness is likely due to varying thickness - not ideal, but no more likely to fracture than the bends at corners and edges. On the other hand if the bottom is uniformly thick (you can check that with liquid) then you're looking at a variation in the index of refraction of that glass, meaning a contaminated or poorly mixed batch. I don't know how likely that is, but if that's the case I wouldn't expect the dish to hold up as well as it should.

[Shel_B]

Another Pyrex question: The instructions for my new Pyrex dish say to only put the dish in an oven preheated to the desired temperature.  Why is that?  For some items that I cook, the dish goes into a cold or cool oven and everything comes to temperature together.  Seemingly, that's unacceptable for these dishes.  Or is that unacceptable for any glass or ceramic dish?

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[weinoo]

I'd just return it.

[Martin Fisher]

It's due to the properties of the failure-prone junky tempered glass that's now used to make Pyrex rather than the traditional resilient borosilicate glass which was what made Pyrex, Pyrex.

The heat is all around more even in a pre-heated oven, which limits stress.

The Pyrex brand was destroyed when Corning, Inc. spun it off back in 1998.

 

That's "progress!"

[andiesenji]

I won't use the "new" Pyrex.  I have a lot of old Pyrex, Corning, Glasbake, Anchor Hocking, etc., amassed over the decades.

 

Recently I did have to buy a "new" glass loaf pan  so I found one of the amber "Visions" ones on etsy.  It can go from fridge to oven to table, which is not safe with the new Pyrex.

 

I have several things that start in a cold oven.

 

Also, I want stuff that is made in the U.S. 

 

Some of the Anchor Hocking - although it states on Amazon that it is made in U.S.A. - the box, on arrival says Made in China.  It was returned.

[Shel_B]

I won't use the "new" Pyrex.  I have a lot of old Pyrex, Corning, Glasbake, Anchor Hocking, etc., amassed over the decades.

 

Recently I did have to buy a "new" glass loaf pan  so I found one of the amber "Visions" ones on etsy.  It can go from fridge to oven to table, which is not safe with the new Pyrex.

 

I have several things that start in a cold oven.

 

Also, I want stuff that is made in the U.S. 

 

Some of the Anchor Hocking - although it states on Amazon that it is made in U.S.A. - the box, on arrival says Made in China.  It was returned.

 

Fortunately, there are several old, similar pieces here as well, and there's no need for me to bake or cook in the new Pyrex dish.  I'll use it for other purposes ... glad I didn't have to pay for it.

[Shel_B]

The streaks are a surprise. Care to post a photo?

 

Doesn't show up well at all....

[Smithy]

Doesn't show up well at all....

 

That's a shame, but not surprising.  How about more of a description?  Are the streaks opaque, like they might be very fine bubbles?  Are they colored?  Are they darker but still clear, like a finely-grained wave pattern going across your ripple pattern?  I'm fishing here...just trying to work out whether they might be impurities in the glass as opposed to uneven casting.

[Smithy]

I don't see the rationale for saying that the dishes must be put into a preheated oven. If they're especially heat-sensitive they should be brought up to temperature along with the oven, to minimize the temperature differential. Hmm.

[Martin Fisher]

When an oven is in the process of heating up...the heat is greater on the bottom part of the pan....that's uneven heat.

[weinoo]

Yeah, but isn't placing a pan on a preheated oven shelf subjecting that pan to instant temperature change?

 

I'd still return it.

Edited December 30, 2014 by weinoo (log)

[Thanks for the Crepes]

Shel_B,

 

There is much evidence that the new Pyrex and Corning Ware are not what they used to be.

 

With the vintage, I can put a refrigerated dish into a preheated oven to cook, and do it often successfully (for thirty years). I've never had reason to put them in a cold oven. I also have frozen stuff in them, and then thaw in the fridge before baking in a preheated oven. 

 

Even with the older stuff, the instructions say to avoid temperature shock. I hate to admit that I forgot that one time and ran cool water into a hot dish in the sink and it shattered, but didn't shoot shards of glass all over the kitchen and into my face like the new ones will do.

 

The reason the instructions call for a preheated oven is to minimize the manufacturer's and distributor's exposure to liability and secondarily to reduce your risk of injury.

 

The striations on your vessel indicate manufacturing defects, I think.

 

Good luck suing Chinese manufacturers. They sent boatloads of toxic Sheetrock to us that had to be removed and replaced at great cost, and I've yet to see any report of compensation. Go back on the American distributor; that's your only recourse. Or just throw it away, if you hate returning stuff, or use it for something else, like you said.

 

Google exploding Pyrex or Corning Ware and you'll find many examples, including several on this site, and one started by you, entitled "Glass Pie Plates" in September 2 years ago. It might have been your thread that led me to research it more widely, but I can't remember more specifically now.

 

Anyway, I remember a woman reporting a new Corning Ware casserole exploding on her when she opened her oven to check on it. She was wounded by the scalding glass shrapnel in the legs mostly. Apparently the explosion was from the cooler air from outside the oven contacting her casserole. The containment of the oven's roof limited it. I surely wouldn't want that to happen to anyone with a wall oven. That would be beyond horrible.

 

Return your piece, or just trash it. It's not worth an injury, perhaps a very severe one.

 

I'm lucky enough to own many Pyrex and Corning Ware pieces when they were made in USA that are marked so. I adore and rely on them.

 

But after reading about the new stuff that's available I'm not buying anything more unless it's vintage.

[Norm Matthews]

Just FYI, thermal shock breakage will occur to vintage Pyrex when using it directly on "modern" electric coil stoves.  Pyrex coffee pots and double boilers were designed to use on gas stoves and need to be elevated above more modern electric  stoves with a  wire coil designed for that purpose.  They can withstand uneven heat but not extreme and direct temperature variances.

[andiesenji]

Incidentally, Arc International, located in France, still produces excellent ovenware from borosilicate glass, much for the "industry" supplied to restaurants, hotels and etc., but occasionally you can find nice pieces on ebay at very reasonable prices.

 

I have several Arcoroc baking dishes that were widely available a decade or so ago and filled a niche that Pyrex and Corning had neglected for some years - pieces that were sturdy enough for general kitchen use but also attractive enough to be presented at table.

At one time Costco carried a full line of the glass ovenware, which is where I bought most of mine. 

 

They are thinner than the Pyrex but are stronger - I had one slip out of my hands when removing from the dishwasher and bounce on the floor without breaking!  Try that with Pyrex - not going to survive.

 

I also have Arcoroc jam jars that I use for baked custards, small souffles, etc. 

[Thanks for the Crepes]

I had a boyfriend/fiance (we never married, thankfully) who owned the amber set of Visions cookware.

 

We actually used them on the stovetop of our electric range with no problems. I loved being able to see what was going on inside the pots. I was really skeptical at first, but he assured me it'd be okay, and it was. This was before even tempered glass lids for stainless cookware were widely available. I really like those too.

 

Don't miss the ex, but I sure miss the Visions cookware. I wish they were still available in that quality. As the daughter of an engineer, I find it amazing that you can actually put a transparent GLASS pot on an electric coil and not have a disaster. I consider the old Visions line to be a major engineering feat, and I wouldn't believe it if I hadn't seen this with my own eyes.

 

I remember having a white ceramic looking coffee percolator in the 70's with the iconic trio of blue flowers. It was used on a gas stove. I can't remember the instructions or using it on an electric stove, but it always worked great.

 

I still have a Corning Ware pie plate with the white ceramic, blue flower design. I got that in 1986 at a "yard" (actually the top floor of the Masonic Lodge in Cary) type sale the Eastern Stars were having when I worked there. It still looks new, although I use it all the time.

 

The loss of American made Corning Ware and Pyrex is a great loss to anyone who cooks. I really feel sorry for the young cooks coming along now.

[Porthos]

So if I look at a piece of Pyrex and it says USA, it is still the old formula?

[andiesenji]

Pyrex stove top cookware was sold decades ago, along with a small wire "trivet" for use on electric stove tops with the flat metal coil.

They could be used on "hot plates" that had ceramic grooves that held wire coils because the glass did not come in direct contact with the metal coils.

I have several glass vacuum pots that came with that type of "stove" ...

 

I have a lot of very old Pyrex that still functions beautifully.

You can see several pieces on my blog - fry pans, double boilers (including one with wooden handles made during WWII) .

I also have a tea "kettle" still in the original box with the wire trivet.

It cost 9.95 in 1979 (still have the original receipt)

 

The other one, no box, I purchased in 1961 - it is a "Flameware" series "L"  (on the bottom, difficult to photograph)

and the one in the box is a series D1 - also Flameware.

 

Right on the stainless band it says do not use on electric range without grid and do not boil dry.

[andiesenji]

So if I look at a piece of Pyrex and it says USA, it is still the old formula?

Yes, if it says USA right on the piece itself.