Some Questions About Pyrex and Corningware

[thock]

Thanks, all y'all. I had read the instructions (always do), but had heard some horror stories about people putting cold Pyrex in hot ovens and having it essentially disintegrate.

I STILL don't like the idea of non-borosilicate bakeware, but that's me.

[Darienne]

Consumer Reports this month (well, January 2011) has a very useful report on Pyrex: "Glass bakeware that shatters". There it is out in the open at last.

[emannths]

I once had a tempered glass shower door explode on me once. THAT was cool. The cracks instantly propagated though the pane, then it fell into the tub, where the little pieces continued to pop apart. It looked something like

, but more dramatic because it was in the freakin' shower. If you haven't experienced this, you're missing out on one of life's great thrills!

Anyway, my understanding is that when tempered glass breaks, it will shatter into these small little nuggets. Which makes it a pain to clean up, it also means that there are no sharp, jagged shards. So don't avoid it because you're worried that you're going to be sliced open by a baking dish.

[Darienne]

Anyway, my understanding is that when tempered glass breaks, it will shatter into these small little nuggets. Which makes it a pain to clean up, it also means that there are no sharp, jagged shards. So don't avoid it because you're worried that you're going to be sliced open by a baking dish.

On the contrary, although that is what the manufacturers claim, the Consumer Report article states that many of the dishes have indeed exploded into 'sharp shards that go flying'.

One consumer reported: 'Glass shards flew across the kitchen, including "multiple large glass fragments" and hundreds of "microscopic shards penetrated her face and eyes, causing serious injury and loss of vision"...'. p. 47, Consumer Reports, Jan 2011.

Scary as h*ll. Since I first learned about the change in glass composition in the Pyrex and other similar dishes, I have been buying old second hand pieces. Still you have to be careful with dishes which are scratched.

[andiesenji]

Andie,

Do you put your borosilicate glassware in a pre-heated oven? I haven't been, because I'm concerned that it will crack. However, I do remember my mother putting Corningware and Pyrex in a pre-heated oven.

Sorry, I missed this question last month.

I take Pyrex filled with stuff from the freezer, place it on a sheet pan and then into a pre-heated oven.

I do this routinely anyway, I simply don't put any vessel that is subject to breakage, whatever is in it, directly on an oven rack.

I don't do this to protect against heat shock but to prevent spill over and also because I once broke a pie plate when I stuck another pie plate in the oven a bit too forcefully.

I was not a happy camper cleaning up the debris from a pecan pie on the lower racks and on the floor of the oven and because some of the stuff had run through the holes in the sides I had to take that out and clean down around the burners.

As I said in my earlier post. I have glass baking dishes as well as stove top vessels that were made in the first half of the last century and they still function just fine.

I have an instruction card that was in a box with a Pyrex "Flameware" double boiler and it stresses that after removing from the stove top only place the hot pot on a folded towel, a wooden trivet or a cork hot pad. It specifically warned against setting the hot pot on an enamel counter or table top (common in those days), onto a tiled surface or into the sink, with or without water.

Frankly, I don't like the newer Pyrex made from soda glass. I think it scratches easier. I have one Pyrex 10 inch pie plate with the earliest Pyrex round logs on the bottom (dates it to 1919-1932) which has fewer scratches than some I purchased in the early '90s and it has been in constant use.

As a matter of fact, I just published a page about glass cookware and bakeware on my blog this morning and a photo of that pie plate is the first one on the page.

My blog page on this subject.

Edited December 9, 2010 by andiesenji (log)

[thock]

It was a year ago, last month, but that's ok.

Thanks for the info and the link to your blog post. I'll have to read it later. The spill prevention idea is a good one, and one I'll have to adopt because I'm a big klutz.

I agree that the newer stuff seems to scratch more easily. I have been picking up old(er) Pyrex at thrift stores and yard sales, but sometimes it's hard to determine what's "old enough." I've pretty much narrowed down that if it has the all-smalls "pyrex" on it, it's not old enough. But some of the all-caps PYREX might not be, either.

I wish shipping from Europe was cheaper. <sigh>

ETA: Do you happen to have a list of the marks and what years they were used somewhere on your blog?

Edited December 9, 2010 by thock (log)

[Dakki]

Collecting vintage glass bakeware is pretty hardcore.

I have a load of the stuff that I liberated from my mother. It was supposedly some of her wedding presents so that would date it to the early or mid 70s. Is this the good glass or no?

[andiesenji]

It was a year ago, last month, but that's ok.

Thanks for the info and the link to your blog post. I'll have to read it later. The spill prevention idea is a good one, and one I'll have to adopt because I'm a big klutz.

I agree that the newer stuff seems to scratch more easily. I have been picking up old(er) Pyrex at thrift stores and yard sales, but sometimes it's hard to determine what's "old enough." I've pretty much narrowed down that if it has the all-smalls "pyrex" on it, it's not old enough. But some of the all-caps PYREX might not be, either.

I wish shipping from Europe was cheaper. <sigh>

ETA: Do you happen to have a list of the marks and what years they were used somewhere on your blog?

The earliest Pyrex marks had a small circle with PYREX in all caps and with dollar signs above and below the R and around the top and bottom of the circle U.S. Reg. Pat.Off. No patent number yet.

Later pieces had pyrex in small case in a circle with a patent number and the logos have varied slightly over the years.

The early stove top stuff always had the flame logo and "Flameware" in the backstamp name.

Some history sources date the change over from borosilicate glass to soda-lime glass at Pyrex to 1988 and some to 1990 when the cooking products division was changed to World Kitchen.

Pyrex still manufactures laboratory glass using the same borosilicate formula that has been used for many decades.

Edited December 9, 2010 by andiesenji (log)

[thock]

Oh thanks! I have a selection of Pyrex and other brands of glassware. Here are some of them. Your post helped me to determine that some of them might be quite old.

The two lower ones in this photo are small, maybe 6" diameter. The one on the left says T.M. REG, but no numberThe one on the right is a Glasbake which says U.S.A. 464 (?) on the top and bottom. The upper right-hand one is one that has the PYREX in a circle with T.M. REG U.S. PAT. OFF. and 603 and B-N. No dollar signs, though. The upper left one has PYREX with the registered trademark symbol, 209 9 INCH, TRADE MARK, BB-9 above the PYREX, and below, MADE IN U.S.A., FOR OVEN BAKING ONLY.

The upper-left ones in this photo are deep casseroles, I think, 2 qt. Anchor Hocking Fire-King ovenware. The upper right one says PYREX in an ellipse with "de CORNING" under it on one handle, and on the other, FRANCE in another ellipse.

The loaf pan is a Fire-King 1 qt with T.M. REG. and MADE IN U.S.A. on it.

The oval casserole has PYREX CORNING NY USA on it. The rectangular pan has T.M. REG., PYREX, U.S. PAT. OFF in a circle, and one of the handles is chipped.

Thank you!

[Darienne]

October 2011 Consumer Reports update on glass measuring cups, bowls and baking dishes with the rather distressing title "Shattered Glass". It appears that the manufacturers, such as Pyrex and Anchor Hocking, are still blaming consumer misuse of the products upon all accidents.

[Katie Meadow]

I have my share of hardware store Pyrex: pie dish, standard 8 x 8 and 9 x 12, a loaf pan, measuring cups etc. Everything is at least 15 to possibly 40 years old. Two weeks ago we were having dinner and heard a scary noise. My trusty 2-qt pyrex measuring cup that was sitting quietly on its shelf simply cracked into three pieces with no help from anyone. There were no previously visible cracks or flaws in it that I'd noticed. This got heavy use, primarily as a mixing bowl. It was typically hand washed, drain dried and put away. I certainly hadn't used it any differently recently than I have in the last two decades. Poltergeists? I bought a new one; we'll see how long it lasts.

[Darienne]

I have my share of hardware store Pyrex: pie dish, standard 8 x 8 and 9 x 12, a loaf pan, measuring cups etc. Everything is at least 15 to possibly 40 years old. Two weeks ago we were having dinner and heard a scary noise. My trusty 2-qt pyrex measuring cup that was sitting quietly on its shelf simply cracked into three pieces with no help from anyone. There were no previously visible cracks or flaws in it that I'd noticed. This got heavy use, primarily as a mixing bowl. It was typically hand washed, drain dried and put away. I certainly hadn't used it any differently recently than I have in the last two decades. Poltergeists? I bought a new one; we'll see how long it lasts.

Very distressing. Gave me the early morning willies.

I would assume that the new one will not have any useful qualities of the older ones. If you read the Consumer Report issues, this current one and the earlier one, Jan 2011, you will get quite an insight into the situation.

Re-quoting from my earlier post from that Jan issue: 'Glass shards flew across the kitchen, including "multiple large glass fragments" and hundreds of "microscopic shards penetrated her face and eyes, causing serious injury and loss of vision"...'. p. 47

Aarrgghhh.

[mgaretz]

I haven't broken a clear glass item yet, but I have been in the kitchen when a Corelle item has broken (essentially the same tempered glass). They explode into thousands of tiny shards and few bigger pieces. The shards are needle sharp and go everywhere. So when one breaks it's a mess. The upside is that they are very durable, so I still use them.

[Lisa Shock]

I would like to mention that Duralex glassware is still tempered glass of high quality. I have manged to get some so-called 'used' Picardie items on amazon that were customer returns with damaged packaging but brand-new, unused merchandise at big discounts.

[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]

What's the practical difference between Corningware and Pyrex. Can some things be done with one and not the other, such as being used on a stove top or going from the refrigerator or freezer to the oven? Is one better for certain types of cooking, or cooking certain foods?

Edited January 14, 2012 by Shel_B (log)

[rotuts]

I recall corningware ( the white stuff ) can be used on top of the stove on a burner.

I know that pyrex can not. but check their web sites first. corningware may have different types. Im thinking of that white set with the glass lid thats been around since the begining of time.

[gfweb]

There's also more than one pyrex IIRC. Old pyrex is tougher than new pyrex I think I remember reading.

[Shel_B]

I alsoread that the new Pyrex is not as "tough" as the older Pyrex.

As for the Corningware, I'm thining about the white kind, as that's what I have.

[Porthos]

FWIW I never put my Corning Ware or Pyrex over an open flame, just in the oven.

[Shel_B]

CorningWare for the Stove Top

Problems with New Pyrex?

Edited January 14, 2012 by Shel_B (log)

[Jmahl]

Pyrex is tempered glass and can not tolerated rapid temperature changes. Corningware is a ceramic material - can tolerate rapid temperature changes. Both can go on the stove but pyrex needs a wire spacer if placed on an electric stove. Hope I have this right since the tech. folks on egullet hold you to a very high standard.