On Thu, 06 Jul 2006 16:41:41 GMT, cavelamb
wrote:

I think the wet ice is acting as insulation to protect the food stuff from
the dry ice - depending on how close stuff is to the dry stuff.

That is exactly the right way to use dry ice in a cooler box.
Otherwise there are problems with things that come in direct contact
such as beverage cans which will quick freeze and rupture.

The one exception is carboard juice boxes which don't seem to mind
being frozen, and actually make an excellent ice substitute if frozen
in advance.