Weird issue with vacuum flask

[bazzabear]

I don't think it's worth the price of the gas to keep a pan of water at near boiling for an hour.

Given that even when we've opened it, we'll only be throwing it away anyway I guess.

But I do agree with your point and I did dry it off before trying to open, but it obviously hadn't been heated enough (and that was a good twenty minutes on the hob). I was about to put it back in the pan when my wife and I agreed there was no point.

 

[Raymond Lin]

Ah - You didn't specify fixed. I just presumed the bowl had hot water poured into it from a kettle or something, whereupon it'd start cooling rather unhelpfully... which is why I suggested what you pretty much just confirmed!

TL;DR - Yeah, what you said... which is what I said... but not what she said.

Fixed, alas Sous Vide...which is what you do in sous vide?

 

[Raymond Lin]

I don't think it's worth the price of the gas to keep a pan of water at near boiling for an hour.

Given that even when we've opened it, we'll only be throwing it away anyway I guess.

But I do agree with your point and I did dry it off before trying to open, but it obviously hadn't been heated enough (and that was a good twenty minutes on the hob). I was about to put it back in the pan when my wife and I agreed there was no point.

Lol, I would have done it to prove my theory works (or not)

 

[bazzabear]

I won't pretend I wasn't tempted. Wifey seemed to think I was about to make it explode in my face though. (Fnar)

 

[PermaChanged]

Insulate me as much as u like, insulate my girlfriend and u gone 2 far.

 

[Raymond Lin]

I won't pretend I wasn't tempted. Wifey seemed to think I was about to make it explode in my face though. (Fnar)

In theory, if you warm it in water, it would only go back up to max 95c ish, it wouldn't get to 100c.

What did you put in there anyway? was it straight from the pan? or was it cooled a tiny bit?

 

[Blackjack Davy]

Um, dont' do it up so tight next time? In the meantime stick the cap in a vice and wrench the sucker off

That being said the 1/2 litre ones don't retain heat too well since heat loss contraction seems to be the issue here the 1ltr ones should be good for at least 6 hours whether you still want to drink the coffee after its been stewing that amount of time is another matter

 

[ttaskmaster]

Fixed, alas Sous Vide...which is what you do in sous vide?

Kind of, but not usually at 95ºC.
Sous Vide is 'under vacuum' and generally low temperatures for several hours... Something like 50ºC for 7-8hrs. This is just about getting heat through the insulation and into the inner compartment enough that it reverses the suction. The vacuum part is not necessary in this case and the low temperatures just mean it'd take much longer, if it even worked at all. A blow torch or a heat gun could, in theory, do just as good a job.

 

[Raymond Lin]

Kind of, but not usually at 95ºC.
Sous Vide is 'under vacuum' and generally low temperatures for several hours... Something like 50ºC for 7-8hrs. This is just about getting heat through the insulation and into the inner compartment enough that it reverses the suction. The vacuum part is not necessary in this case and the low temperatures just mean it'd take much longer, if it even worked at all. A blow torch or a heat gun could, in theory, do just as good a job.

The method of sous vide, keeping it at a constant temp....the method, not the specific of temp.

anyway, side tracking here.

 

[bazzabear]

Um, dont' do it up so tight next time? In the meantime stick the cap in a vice and wrench the sucker off

If you read the thread you'd see that:

1) It isn't done up too tight, that isn't the cause of it not coming off.
2) Putting it in grips hasn't worked. You certainly could grip it hard enough so it wouldn't slip - but you'd destroy it in the process.

 

[bazzabear]

What did you put in there anyway? was it straight from the pan? or was it cooled a tiny bit?

It wasn't what you'd call haute cuisine! Super noodles.

And I suspect my wife put them in as hot as she possibly could, to try to maximise how warm they would still be 5 hours later.

 

[Danm54]

Did you try standing it upside down in the boiling water? Heating the lid/threads of the lid would help more than heating the bottom of the flask.

 

[Luke]

Return it to Amazon, contents included.

 

[theone8181]

Surely by now even the best thermos must have hit equilibrium so have you managed to just pop it apart?

 

[div0]

Drill the lid, release the pressure, declare yourself victorious, then bin.

 

[d_brennen]

Return it to Amazon, contents included.

I like this idea, especially if OP didn't get it from Amazon in the first place.

 

[bazzabear]

Surely by now even the best thermos must have hit equilibrium so have you managed to just pop it apart?

Equilibrium in temperature you mean? But the issue isn't a temperature differential, it's a pressure differential, caused by the interior cooling.

if I took it to space, it'd open really easily.

 

[bazzabear]

Drill the lid, release the pressure, declare yourself victorious, then bin.

I have told the missus I could solve it in a moment with a drill.

 

[theone8181]

Equilibrium in temperature you mean? But the issue isn't a temperature differential, it's a pressure differential, caused by the interior cooling.

if I took it to space, it'd open really easily.

But there shouldn't be a pressure difference once it's cooled as the hot contents will not be hot anymore? Or is that the problem, in which case its not kept it warm till lunch so why bother with the flask?

 

[bazzabear]

But there shouldn't be a pressure difference once it's cooled as the hot contents will not be hot anymore? Or is that the problem, in which case its not kept it warm till lunch so why bother with the flask?

I'm not getting you.

When the flask was sealed, the pressure was equal with the outside. The contents have then cooled and therefore the pressure within the flask has reduced. It's the cooling which has caused the pressure differential - it doesn't get rid of it.