This meant that by measuring the change in the temperature of the water inside my cans I could determine how much heat had left the water through the can. If I wanted to I could also calculate the thermal conductivity of the metal. I got ridiculous numbers for the thermal conductivity of my metal cans. After some thought I realized that there was another important process taking place that I had not taken into account. The metal was conducting the heat from the water to the air but until the air carried the heat away the water wouldn't cool down.
Air picks up heat by conduction but carries it away via convection.
This is a slow and not very efficient process. What I was measuring on the lab bench was the same thing that was taking place on the refrigerator. What I really needed to know now was how much heat could the air pick up from the metal in some period of time. I went back to work and reassesed my numbers. To my suprise there was not a lot of difference in the results from the different cans.