I bet you’ve been using these your whole life without knowing it: in non-USA thermoses, the lid releases pressure before becoming mechanically free. You’d hear a “pop” and then the lid has to be twisted slightly further before it can be removed.
replyNot all safety features have to be obvious/obtrusive.
I see no hole in the metal anywhere on the inside. The only non-metal part that touches the inside is a rubber(?) gasket/ring thingy that sits above the thread and is squeezed by the lid, which I take out to clean and there's only metal under there as well. How would this work? Did I get the exceptional model that doesn't have one and just didn't look at other models closely enough?
replyHuh. I’d imagined the threading in the cap could be made this way
reply