Dear consuelo: A long time ago I read in a book that Mexicans used to cool drinking water by storing it in a large unglazed ceramic container, which leaked enough water so that the outside was constantly wet. The evaporation of the outside water cooled the container. I believe the name for the container was "olla". When I was on the troopship, our drinking water was made by evaporation and condensation of sea water, and the bubblers delivered very warm water. I covered my canteen with a sock, which I wet when filling the canteen. Evaporation would get rid of the warmth, though I could never get it really cool. Would you call a canteen like that an "olla"? I did, because I didn't know any other word.