Definitely plastic wrap .. Alum foil would contain the "cold" ambient temperature inside the capsule and prevent ambient warm temps from the room to penetrate.
will ice melt faster wrapped in aluminum foil or plastic wrap?
Aluminum foil.
Foil is a much better thermal conductor than plastic. Wrapping it in plastic will insulate it. And inhibit heat flowing to the lower temperature of the ice.
If you can ever get this site to load, it's got the answer:
www.answers.com/Q/Will_ice_melt_faster_on_plastic_wrap_or_al
I thinkthe plastic wraped ice will melt faster