Quickest way to boil a kettle, in a car?

[charles]

but - the steel ones don't break if you drop them ;-))

[NY]

Couldn't they use a non-conducting (plastic) ring to join the inner and outer skins, or would there be problems keeping this air-tight to maintain the vacuum?

Alternatively, I wonder why there aren't vacuum flasks which are all-plastic (eliminating the need for a plastic-steel joint at the neck).

[Robin]

When I've broken a flask I've never seen a steel neck connector left over among all the glass. Once upon a time maybe. But not for many years now. See eg

Is there a plastic at a reasonable price with the rigidity necessary to sustain a partial vacuum?

PS

When I buy a Thermos with the space in the stopper for sugar etc I cut a piece of Kingspan etc to be a tight friction fit it. I've not measured the effect on heat loss but it certainly stops the top of the stopper getting so warm.