Weird issue with vacuum flask

bazzabear

bazzabear

bazzabear

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My daughter has one of these:

https://smile.amazon.co.uk/Pioneer-...06XGKFKVM/ref=cm_cr_arp_d_product_top?ie=UTF8

This lunch time, she had to be given a school lunch because neither she, nor any of the teachers, could get the top off.

Back home with it, and it seems that the food inside cooling has created such a strong negative pressure that as you unscrew it, it's sucking the lid back down across the thread - you can hear it banging across them.

So. Any theories on how to non-destructively get the lid off?
 
adolf hamster said:
heat it up?
Click to expand...

Ding ding ding.

If the goal is equalise internal pressure and since the base is stainless steel then I’d try sitting it in hot boiling water first, if that doesn’t work then put it direct on a gas hob on low heat. Using an oven mit to protect yourself and twist it when it warms up.

or the safe way is a pan, water, heat up pan, stick this thermos in it like you are melting chocolate.
 
Last edited:
Raymond Lin said:
Ding ding ding.

If the goal is equalise internal pressure and since the base is stainless steel then I’d try sitting it in hot boiling water first, if that doesn’t work then put it direct on a gas hob on low heat. Using an oven mit to protect yourself and twist it when it warms up.

or the safe way is a pan, water, heat up pan, stick this thermos in it like your melt chocolate.
Click to expand...
Might not very practical at a school lunch.
 
bazzabear said:
I guess, given that it's very purpose is to insulate the interior, it might need to be in the pan for quite a long time!
Click to expand...

If the contents have cooled enough to cause this issue in the first place, I’d suggest that the flask is probably failing in its purpose anyway.
 
Take the same flask every day and get free school lunches forever more? Duhh.
 
Rubber bands around the top and lower, for better grip.
Cut some strips off an old inner tube of suitable diameter and stretch them around.

theone8181 said:
Oh I see, small fire in a lunch box then:D. I've never thought of using a flash for that, I've always thought tea/coffee.
Click to expand...
Spaghetti is a popular one for flasks. Cooks in the flask, and is ready at lunchtime.
 
are you sure lids threaded plastic stopper is not rotating, independant of the stainless top - which might explain a noise.
 
I assume the flask doesn't really work effectively as a vacuum to keep the food inside hot then? Since the interior has sufficiently cooled to produce such negative pressure.

Could be a mixture of that and seals that are very good. Either way, sandwiches from here :p
 
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