Aluminum Homemade Boat Why Does This Recipe For Homemade Ice Cream Require Aluminum Foil?

Why does this recipe for homemade ice cream require aluminum foil? - aluminum homemade boat

I have ice cream with the following recipe, which was very creamy and smooth. It was more like ice cream ice cream, but it is still not soft contact lenses:
http://www.foodnetwork.com/food/recipes/recipe/0, FOOD_9936_21180, 00.html

I was very lucky that I happen to have a piece of paper on hand, but. Normally, if I'm missing something - like an ice machine or coffee cans ... So I asked myself if I'm stuck without a film, but the desire to suddenly this ice does not touch me 10 minutes the pan line results to ruin? Why do I need the line of the pan with aluminum?

I would like the waste of ingredients at the right time if they avoid taking the line.
Any ideas would be greatly appreciated. Thank you. =)