A typical thermos is double-walled, with a vacuum gap between the two walls for insulation. My idea is to add a third wall, so there are two gaps, but instead of a second vacuum gap, the inner gap is filled with that stuff they use in those ice packs that you can re-use. All you do is stick it in the freezer the night before, and the stuff in the inner gap freezes into ice (ice-like, anyway) to encase the contents in ice to trap heat better. The outer vacuum-gap is still there to help keep the inner layer frozen longer. Yes, this will be slightly bulkier than most thermoses (thermosi...?) but it'll keep it colder longer.

Note: I didn't have much time to research this (I'm using my friend's computer) so if this is baked, I aplologize and will make necessary adjustments next time I visit.
-- 21 Quest, Mar 18 2007

Hot cubes http://www.halfbake...om/idea/Hot_20cubes
[xaviergisz, Mar 18 2007]

[+]

The only obvious potential problem I can see is that such material might expand or contract a lot with temperature change. After all, they do almost always come in those flexible bags. But I guess that if the walls are strong enough to survive a vacuum, they could probably handle slight pressure changes from the ice pak stuff too.

The other concern, of course, is expense vs. usefulness. My vacuum thermos keeps stuff cold for many hours on end. More than that doesn't seem terribly necessary. But maybe for some people!
-- Smurfsahoy, Mar 18 2007


I was thinking to maybe not fill the gap completely with the liquid, you know, leave just enough room for expansion. Thanks for the input, and welcome to the hb!
-- 21 Quest, Mar 18 2007


or you could add ice cubes (or hot cubes) into the liquid in a normal thermos.
-- xaviergisz, Mar 18 2007


I occurs to me that the "third layer" doesn't actually need to be an entire layer. Instead, you could incorporate it into just the cap. So, you only need to put the cap in the refrigerator or on the stovetop.

Each thermos bottle could be supplied with two caps, so while you're using one of them the other can be waiting ready in the refrigerator. You can also instantly "convert" the thermos bottle into a traditional one using a normal cap.
-- IJK, Mar 18 2007


Or make an "ice"-pack that slides in through the neck of a standard thermos. It would add cold, so to speak, without diluting your drink. Hmm, make it soft so it doesn't break the glass.
-- baconbrain, Mar 18 2007



random, halfbakery