Keeping your cool
Did you ever wonder how people kept food fresh in the days before refrigeration? On hot summer days, perishable foods could be kept fresh using evaporative coolers.
Evaporative coolers take advantage of the fact that when water evaporates, it cools the surrounding air. First, the cooler is soaked in water. The water permeates the unglazed clay. Next, it is placed over a perishable food or bottle of liquid (usually milk). As the water evaporates, the air trapped inside the container is cooled.