The principle is the same one that I used years ago when we made homemade ice cream. When you add salt to a ice and water mixture, the salt lowers the freezing point of the water, meaning it gets colder than it normally could. Agitating the can of soda makes the whole cooling process go faster.
- Fill a container with water and add ice to it. (I used a 50/50 mix of ice and water, and performed my experiment in a six-cup measuring cup since I was only chilling one can of soda.)
- Add a handful of salt to the ice. (Rock salt would probably have worked better, but all we had in the garage was something called "ice melt"; I didn't know if it would have the same effect. I used table salt, and it did the trick.)
- Place your drink in the ice water solution and rapidly stir it around. (My hands were already cold, so I used a wooden spoon for this step.)
- Wait two minutes, then test.