There are some interesting principles to note here. The freezing is accomplished by using a mixture of chopped ice and rock salt. Can you explain how this reduces the temperature?

Another interesting point is this: Have you ever seen a milk bottle on a cold winter morning with the paper cover or even the metal cap pushed up, the frozen milk standing high above the top of the bottle? What does this suggest to you in connection with the filling of the ice cream freezer?

It must be noted, too, that a larger amount of flavoring material is needed in a frozen dessert than in one that is not. The frozen custard, for instance, needs more vanilla than one prepared in the ordinary manner. Can you account for this?