04-14-2013, 05:55 AM
You only have to seal the outside surface. if that could be made air-tight, the interior would remain at the same density, even after the air inside had cooled.
A cold hot air balloon, or a partial vacuum balloon, would be the result, assuming the foam could resist compression.
A cold hot air balloon, or a partial vacuum balloon, would be the result, assuming the foam could resist compression.