Ice is at 32°F in it's solid state.
When heat is added to ice the ice turns to water, but stays at 32°F until it's no longer ice.
When salt is added to ice it melts so rapidly that it uses some of it's own thermal energy to turn itself into water. When the ice gives up it's thermal energy it becomes colder and the ice and salt water mix can be as cold as 14° - 15° F.
The cream mixture inside the canister is warmer than the salt water ice mix, so it gives off it's heat to try to stabalize the temperatures between the two mixes, inside and outside of the canister, causing the ice to melt more and the yummy homemade ice cream to freeze more, until it's finally ready to cool someones tongue and tantalize the taste buds on the way to it's final resting spot where ice cream is intended to be.
copyright © 1998-2011 tomsvariety.com