In article >,
"john hamilton" > wrote:

> Knowing that its just not easy to get an airtight seal, the suspicion is
> that it might draw the air out but; it will creep back in again anyway.

You could answer that question readily enough. Does the unit have a
vacuum relief valve that you activate in order to get the lid open
again? If not, then I'd say your suspicion is correct.

Do you really need to post this to six groups? (My newsreader won't even
allow me to respond to that many, so I beheaded two of them.)