This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Set a bowl containing butter, cream or fruit in a saucer and cover the bowl with a moistened napkin, allowing the edges to hang in a larger saucer filled with water, and place the whole in the air out of the sun's rays. The article to be kept cool may also be placed in a pan with an earthenware crock turned over it and covered with a small towel or cloth, the edges of which extend into another outer pan partly filled with water.
The method can be applied on a larger scale by using a shallow galvanized pan which will contain many articles and more water. This manner of cooling is especially adapted to camping parties and will prevent sloppy butter, sour milk and spoiling fruit. The articles are also kept free from ants and flies. - Contributed by C. B. Hosford, Swansea, Ariz.