"eastender" wrote in message
news:2013031521173976111-nospam@nospamcom...
On 2013-03-15 21:15:52 +0000, Alan Braggins said:

More seriously, was the lunch warm when it was put in and created a
partial
vacuum when it cooled? In which case put it in hot water for a while?
(Might even help if that wasn't the original problem.)

Yes it is for hot food.

That's certainly the problem.

I get the same problem with the marmalade and relish
I make myself. When I put the lids on the glass jars when
they are still stinking hot with the freshly made contents,
it can be a real bugger getting the lid off when you first
want to use it.

I just microwave the jar for a minute or so and that does
heat the contents up enough to allow you to get the lid off,
but that wont work in your case with the metal container.

Putting it in boiling water will.

Just let it cool down before screwing the lid tight next time.

Good plan - I'll try that. I can't believe the top is cross-threaded as
it's on square.

Yeah, its just the lower internal pressure effect.