Exploding Pyrex?

[Xenodius]

Recently a friend of mine left some chicken in a 13x9 glass Pyrex dish in the oven (At 375 F) too long, and noticed smoke from the kitchen. They promptly ran into the kitchen and opened the oven, and in less than two seconds their kitchen was sprayed with a hail of glass and hot oil. The glass was even on the opposing countertop! (~8 feet away, and *higher* than the pans origin, obviously) I had never heard of such a thing, but did some reading and found this article:

http://www.consumeraffairs.com/news04/2006/03/pyrex_panic.html

Quite surprising, I thought Pyrex was adequate quality borosilicate glass for medium temperature lab-work... I guess I was wrong. Obviously the pan shattered due to the temperature difference when opening the oven-- the timing is unfortunate. But I thought Pyrex could withstand that.

Comments, input, explanations? This was baffling to me... (Under 400 degrees...!?)

[megalomania]

A crack, chip, or other imperfection can cause a very significant stress point in even the best glass. Pyrex dishes are still subject to the quality variations of any mass produced product. Nobody expects a brand new car to break down just after driving it off the lot, but it happens more than anyone would like.

[Dr. M]

I can attest to a similar experience. My lab recycles used glass beads used for cell lysis via acid-washing, rinsing until neutralized with ultra-pure water, and baking in an oven at 300 Celsius to fully dry and eliminate potential protease/DNAse/RNAse activity. We bake the glass beads in pyrex dishes, and the cheapest source for borosilicate dishes like this is commercial bake-ware.

Unfortunately, sometimes one forgets about his 'baked beads'; in this particular case, a technician who was leaving our lab for other employment put a dish in the back corner of the oven and neglected to tell anyone. Fast forward 3 weeks to my discovery of this dish while putting in a rack of glass pipettes to bake. Naturally, I removed the dish of beads and placed them on a wool pad (i.e. an autoclave glove) on a nearby stainless steel cart to cool.

What followed roughly 30 seconds later was the single loudest non-firearm/non-pyrotechnic 'BANG' I have ever heard. I had micro-fine shards of glass embedded in my shirt, and in my right forearm. Luckily, my face was far enough from the epicenter that I didn't have any eye damage - just glass in my goatee. What good fortune to have such a well-timed blink; there's no way it was sheer reaction time that saved me.

We found glass in places up to 20 feet away from the tray - definitely an 'educational' experience to say the least.

My thoughts have always been that baking for that long 'compartmentally normalized' certain regions of the dish to one state of tension/shear force, while doing the same to neighboring regions - creating massive stresses within the glass which overcame the threshold of integrity once the dish began to cool unevenly in the still air.

If only I'd have had a pair of polarized glasses, what a pattern I probably would have seen in that dish... right before it blew up in front of my face, that is.

[The_Duke]

On the subject of exploding glass; Prince Rupert's Drops (http://en.wikipedia.org/wiki/Prince_Rupert%27s_Drops)

[ChippedHammer]

Pyrex is not made of borosilicate glass anymore, I found this out firsthand when I dropped a old pyrex jug and replaced it with a new one which promptly exploded when I put it above my gas burner.

Apparently they are made out of soda-lime glass now.

[aliced25]

The problem is in part from the temperature differation, even borosillicate glass expands when heated (just less so than soda-lime glass). Thin walled borosillicate can cope with larger temperature differentiation than thick glass.

I found out the hard way when preparing phosphoric acids via a MW route, phosphoric acids absorb heat like you wouldn't believe (so does monoammonium phosphate). Unfortunately, whenever I have done this without using a pre-heated oven to place the hot glass in (and sometimes when I have), the glass has given a massive crack and sent razorsharp shrapnel everywhere within about a second.

Anything over 300C is too hot to allow for rapid cooling of even pyrex, I checked this with a couple of the older glassblowing publications and that is where I got the idea of putting it into a pre-heated oven instead...

PS Someone recently told me that Corning have lowered the specs of their borosillicate cookware. I find this hard to believe, but the reports are beginning to establish a pattern suggesting it is true.

[Charles Owlen Picket]

How does one tell the difference between the old and new glass materials without an accident?

[Gammaray1981]

Hold the edge in an acetylene flame? IIRC, good glass won't then bend after a few seconds, whereas cheaper/lesser glass may sag, or at least be malleable.

[SafetyLast]

Back in my kewl days I had an incident with an exploding pyrex measuring cup.
Like an idiot I was using it for boiling in, trying to make a saturated KCl solution for chlorate production. I added too much KCl and needed to add more water to dissolve it. I foolishly started to add a few ounces of cold water to the near boiling solution, then boom! glass shards and hot water all over. Luckily I was uninjured, but it was a waste of a nice piece of glass.

[genovese6314]

Has anyone ever looked at the Corning Ceramic cookware they are distributing now. I was in Walmart last night and saw a wide variety of glazed ceramic baking dishes. Wondering if they could make a crude crucible. Not to mention the $20 toaster oven I was eying up and the miniature slow cookers that look awfully like a nice flask bath.

*************

Use punctuation.

-Hinckleyforpresident

[hydraliskdragon]

Same, my new pyrex measuring cup exploded/shattered after using it for creating Acetone Peroxide. I had cleaned the cup and dried it. I put it into my storage container and in about 10 minutes, I heard an explosion and this is what I saw.