|Michael Gilligan||09/06/2022 06:58:31|
20289 forum posts
I am posting this in ‘Scientific Instruments’ … but it may be of interest in other areas.
I was shocked to read this note by a respected contributor to the microbehunter forum :
[quote] I have been doing a bit of research on glass in order to solve this riddle and came across a class action lawsuit vs. World Kitchen (Corelle), over exploding pyrex bakewear. It seems that PYREX labwear is still made by Corning but Corelle /World Kitchen was spun off in 1998 as a consumer products division and they make the kitchen stuff. PYREX was originally borosilicate glass but since the spinoff and a bit before, pyrex bakewear has been made from tempered soda lime glass. The borosilicate products are PYREX with all upper case letters, the soda lime pyrex are lower case. There is another differerence too. The colour. A pyrex measuring cup has a decided blue tint when looking horizontally through it's bottom. A PYREX cup bottom is clear. There have been some pretty nasty shatters. [/quote]
Edit: __ i expect there is much more to the story; but this seems a good pace to start:
Edited By Michael Gilligan on 09/06/2022 07:10:25
|170 forum posts|
I have personal experience of a Pyrex jug exploding in a cupboard, probably about five years ago. It had not been used that day and there were no unusual circumstances, extreme weather, etc. and nobody was in the kitchen at the time. It truly exploded, distributing shards of glass throughout the cupboard among the other china and glassware. Fortunately, most of our Pyrex was acquired before the change but the jug had been a more recent purchase.
I remember finding much online comment about the phenomenon at the time and have not bought Pyrex branded items since.
|Mark Rand||09/06/2022 08:59:42|
|1314 forum posts|
This has been the case for a number of years. In the UK and EU, you'll find PYREX borosilicade kitchenware. In the US you'll find pyrex tempered soda lime kitchenware.
1484 forum posts
Have found that recent purchases of “Pyrex” oven dishes develops chips very easily and is no comparison to older traditional Pyrex oven ware. I assume that the chips are probably the first stage of the process whereby the item lets go by exploding! Dave W
|Frances IoM||09/06/2022 09:52:31|
|1283 forum posts|
|A quick kitchen survey showed most of my small stock Pyrex to be old bought in the 70s when I set up my first house but one measuring jug is PYREX(R) made by Corning in USA but "not for Lab or stovetop use" - this was a charity shop purchase some years ago to replace a broken one thus it seems Mark's US tempered glass bears the PYREX marker.|
Edited By Frances IoM on 09/06/2022 09:52:52
8898 forum posts
One of my favourite hobby-horses is criticising the trust folk have in Trade and Brand names, which just labels with no solid connection to who owns the company, where the product is made, what it's made of, or a specification.
Brands often build a star reputation by performing better than the competition due to a temporary technical advantage only to find other producers catch up later and pinch all the profits. In the rough and tumble of commerce, very often all that's left of a once successful company is the brand - everything else good about them is long gone. Brands are often bought from the receiver so their reputation can be used to boost sales of less satisfactory products, perhaps nothing to do with the original product.
But it seems consumers want to believe in brand-names despite their unreliable history. In this example, it seems consumers have assumed lower-case 'pyrex' is the same as mixed case 'Pyrex' and that both must be made of borosilicate glass. Nope! There's no particular reason why they should.
Buying anything, I suggest looking beyond the brand-name, ideally finding a specification and what the current reputation is. Reputations go up as well as down, and the best available at the moment may be a newcomer, or a tarnished name back on the up.
Buying cookware, better I think to look for 'borosilicate', which is a real material, rather a trade-name which could be mere advertising. There is plenty of borosilicate cookware on the market.
No idea what the pros and cons of using tempered glass to make oven-ware are, though it's a useful material for other purposes. Might not be a dodgy as it's presented. Michael's class-action document is interesting, but doesn't quote many real-life examples. I'd expect thousands of injuries if a product sold by the million by a major US supplier really was dangerous. Maybe the application is based on a few rare examples going pop with doing much actual harm.
Anyone else had a car window shatter spontaneously? The cause is often temperature change acting on a stress raiser due to slight chip, and as the glass is pre-tensioned to break into a multitude of small blunt fragments rather than sharp shards, it can let go spectacularly. When it happened to me I described it as an explosion, but as explosions go it was tiny - a pop like a balloon and a scattering of glass granules, hardly any energy in it, and nothing like a hand-grenade!
Could be compensation culture. Have you had an accident that wasn't your fault?
|Mick B1||09/06/2022 12:22:24|
|2224 forum posts|
I'd agree - the integrity of brands has been steadily eroded since about the '70s and very many of them now represent little or nothing more than an exercise in badge-engineering of generic products. Witness the 'Moore & Wrong' debate of a couple of years back - and conversely the respect now generally accorded to genuine Mitutoyo, when in the '70s they were regarded by many as cheapie, low-grade instruments.
I sometimes get YouGov surveys about brands of anything from actual solid products to financial and insurance services, fashion, football and gambling. It seems there's a drive from company marketing departments to support brand preference among customers for anything at all, even though most of us know most of them are now worth little or nothing as assurances of quality.
I have one example to cite on the brand at issue here. A couple of years ago we bought a new 'Pyrex' (don't remember the character cases) measuring jug, which just over a year ago shattered to fragments when dropped from about knee-height onto a vinyl floor. Previous experience would suggest it should've bounced without damage.
Edited By Mick B1 on 09/06/2022 12:25:23
|Nicholas Wheeler 1||09/06/2022 12:51:02|
|958 forum posts|
That's common for toughened glass whatever the application. Although it's usually caused by impact damage(stones thrown up the lawnmower breaking patio door sealed units) they can, and do, just break. But because toughened glass shatters into thousands of tiny pieces, it's often not obvious what the cause was.
One of the churches where I ring has the ringing chamber separated from the rest of the church with a glass wall that is three massive pieces of glass. Each one is two sheets of toughened glass laminated together, and the centre one shows where the fault occurred with the damage radiating from it, all because every piece is still stuck to the plastic between the sheets. We're still waiting for the replacement, as there is a row about who will pay for it to be fitted, even though the warranty covers the cost of the glass.
|Martin W||09/06/2022 13:30:19|
|921 forum posts|
For an energetic fragmentation of glass the Prince Rupert Drops are an excellent example. They will survive the impact of a bullet or hammer blow to the bulbous part of the drip/drop but fracture the tale end the disintegration is explosive, wiki gives a description here and from Popular Mechanics an article with photos of the effect of a bullet hitting a drop and also at the end a slow motion film showing a drop exploding.
|170 forum posts|
I'm always very sceptical about such things when reported in the media, but did indeed find many similar incidents when I looked for them. The most surprising part of my incident was that there was no physical or thermal shock involved. The jug had been sitting quietly in the cupboard for many hours, there was nobody in the kitchen at the time, and it just spontaneously exploded. We heard the noise of shattering glass from another room and were unabe to find the source at first. When I eventually opened the cupboard there were bits of jug everywhere.
I read somewhere that the change from borosilicate to tempered soda glass was due to the latter's better resistance to physical shock, which is apparently the most common reason for breakage.
|2567 forum posts|
Some of my glass kitchenware is marked "JAJ"; I found this online:
JAJ Pyrex dates back to 1922. JAJ is actually short for J A Joblings, a Sunderland based glass company who had fallen on hard times. However, Ernest Jobling Purser, a new recruit to the family business heard of a technique developed in America for manufacturing glassware which would not shatter or crack in the oven.
Of course, it may yet crack in the cupboard!
|Michael Gilligan||09/06/2022 22:49:38|
20289 forum posts
I think the con [nice ambiguous word] is pretty clear from the quoted research:
” Dr. Bradt’s findings demonstrated that borosilicate glass can withstand a 333-degree Fahrenheit change in temperature (hereinafter expressed symbolically, e.g. 333°F) before fracturing while soda lime silicate glass can withstand a temperature change of only 99°F before fracturing. “
Methinks 1919 was a better year for integrity:
Edited By Michael Gilligan on 09/06/2022 22:56:06
|Michael Gilligan||10/06/2022 00:07:06|
20289 forum posts
In case anyone is interested … here’s a link to the full patent document :
|Grindstone Cowboy||10/06/2022 00:52:38|
|894 forum posts|
I recall seeing a photo - probably dating from the 1960s - of a Pyrex bowl stood on a block of ice, with molten metal of some sort (I'm fairly sure the caption said iron) being poured into it. The claim was that it could withstand this without cracking. I am a bit sceptical about it.
|Peter Greene 🇨🇦||10/06/2022 01:29:18|
|559 forum posts|
My guess would be Tin-Lead Solder
|Nicholas Farr||10/06/2022 09:00:42|
3421 forum posts
Hi, the first I remember of PYREX was the craze for smoked mugs and cups, I had a mug back in the 70's but I still have two PYREX saucers and here's one with a Arcoroc cup with some morning coffee. Arcoroc France is tempered glass though.
1919 was a good year for me (no I'm not that old) as it was the year my mother was born.
SOD, I've only ever experienced a shattered windscreen once and it was like instant blindness, a stone whipped up by a car going in the opposite direction, it hit the bottom off side corner of my screen, but the most surprising thing was that it shattered from the opposite side and came across like a curtain been drawn, very scary.
|john carruthers||11/06/2022 13:56:42|
616 forum posts
quick and dirty test for Pyrex, it has the same refractive index as many vegetable oils.
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