May I See A Demonstration Of How Aluminum Foilkeeps Things Colder Than Plastic Wrap?

I don't think either one makes much of a difference when it comes to keeping something hot or cold - they are both just too thin to have any measurable effect.

That said...

I think that aluminium foil would be more effective in keeping something cold/hot because:
1.  It is thicker.  Thickness makes it harder for the outside temperature to penetrate and influence the temperature of the thing.

2. It is made of metal. Metal is a material that holds temperature. It slowly becomes room temperature, while plastic just loses heat/cold.


Get a piece of foil and a piece of plastic that are both the same width and length and at least 1 foot long. Fold each until it is very small but very thick AND the same size as the other. Press each material so that it is as compact and dense as possible (no air bubbles, empty spaces, gap, etc).


For a cold test:
Put both in the freezer at the same time and make sure they are right next to each other. Leave them in for 1 hour or overnight or 30minutes.
Take them out at the same time.
Put them right next to each other and see which one is coldest after 1 or 5 minutes.


For a heat test:
Drop them (at the same time) into a pot of water that was boiled but is now cooling, NOT boiling, (I have no idea if the plastic wrap will melt and stick to the bottom of the pot).     Remove both at the same time (using a ladel or a streiner or a seine or seive or salad tongs)  
put them right next to each other and see which one is warmest after 1 or 5 minutes