The glass lid to our large stock pot just exploded - literally. Any theories as to how or why?
Asked by
hearkat (
22922
)
December 21st, 2013
This is a stainless steel pot with a glass lid that is roughly 20 years old. For a good 15 of those years it went unused because I had move home with my mother post-divorce and we shared most of her kitchen items. However, we’ve been in our home for over three years now, and is is our largest pot that gets frequent use. In the past month alone, it has been used every weekend to make stocks.
My fiancé put the chicken, veggies, herbs, and water in the pot over an hour ago and brought it to a boil the way he always does. He then turned down the heat and let the liquid come down to a simmer before putting the lid on – when he did put on the lid, it was at an angle to allow for ventilation. The metal rim around the glass had some dings in it, so it wouldn’t form a tight seal even it it had been put on flat. After about a half-hour, the glass exploded up and out, all around the pot. Unfortunately, enough glass didn’t clear the pot and fell inside, so we’ve lost everything.
We can’t imagine what might have caused this, so we thought the brilliant physics and engineering and cooking Jellies of Fluther might have some ideas. I’ll post it in Social, so we can still have some fun with it.
Observing members:
0
Composing members:
0
13 Answers
My guess is repeated changes of temperature over a prolonged period of time: putting it in a cold place after use, and bringing it out of that cold place and putting it straight onto the stove. Each time you do that the glass will expand and contract too quickly causing micro-fractures that eventually weaken it until it does what just happened.
@downtide: We keep the pot in the kitchen island – a couple feet from the oven/stove, and the kitchen is the second warmest room in the house (the bedroom above it being the warmest), so the temperature changes haven’t been that extreme… and besides, isn’t cooking glass supposed to be tempered for that reason? Also, wouldn’t micro-fractures cause the glass to collapse into the pot, rather than exploding up and out?
It may have been dropped and slightly damaged/cracked. It may have been subjected to too many and too rapid temperature changes.
@kritiper: As with my reply to downtide, it seems to me that if there were unseen damage, it would have collapsed. I’m not saying that your theories are not possible, it just seemed odd how it exploded.
Aw, I’m sorry… all that work down the drain. I would guess it’s just old age setting in(the lid ,not you!)and there was probably microscopic damage accumulated over many years of use. Exploding- that’s kind of weird. I suppose, though, it’s in a metal rim, so there is some stress on it, and you say the rim had dings in it, so the stress would no longer be even all the way around, as it presumably was when new… so, eventually, boom!
Tempered glass has huge built-in stresses. The outer surfaces of the glass are under compression (trying to expand) while the interior of the glass is under tension (trying to shrink). This contrast is what keeps the glass from breaking under extreme conditions, but it also means that when it does fail, it does so in spectacular fashion as all of those stresses unwind.
What caused the failure in your case is hard to say. Anything that manages to introduce a flaw into the compressed “skin” of the glass can set things off. I’ve had tempered glass tumblers seemingly spontaneously shatter in a million pieces in my hand.
Hmmmm… I was imagining that there would be a more ‘spectacular’ (to use @thorninmud‘s word) explanation, such as the solstice happened just as the water came to a boil or something. Oh well, I guess I’ll just chalk it up to old age, then. sigh
The moon is in the 7th house and Jupiter aligns with Mars…
And peace will guide the plaaanets….
… and LooooOOOOVE will steer the stars!
Glass is inherently unstable – it is actually a solidified liquid, and, given enough time, acts like a liquid even though it appears hard.
As a liquid, it has thin areas and thick areas; it sounds like a weak area finally “blew”.
If there was a micro crack in it, and that crack got filled with steam, and the steam expanded rapidly, that would cause it to explode outwards rather than just collapsing into the pot.
Answer this question 
Composing members:
0
