Sponge cooling is an uncommon practice that allows for the air to become more humidified during the proofing phase of baking. This method can also be called evaporative cooling. Proofing is when the dough rises due to the yeast activating with sugars in the bread. This is the process where dough can nearly double or triple in size based upon the ingredients used. Once proofed, the dough will go into the oven where it can be baked. Evaporative cooling occurs when outside air is brought through a fan, over water in a container to raise the temperature of the water and create humidity. Because the liquid in the water tank has lower kinetic energy the liquid evaporates into the air and energy is absorbed. This is similar to the human body sweating. In the wet sponge method, the same principle is applied using sponges half submerged in water and a pan instead of a water tank. Once the cool air travels over the sponges, the temperature is either colder or hotter depending on the outside air. When the air needs to be cool and less humid, ice water is used. When the air needs to be warm and more humid, hot water is used.