Being exposed on all sides, the water will freeze in from one hour to three hours. A bucket of hot water poured into the space between the tanks will loosen the cakes of ice, each weighing 200 pounds. Four tons of ice will last the average family a year. The cakes may be packed away in the icehouse as they are frozen. CHAPTER XXVI HOME COLD-PACK CANNING To save vegetables and fruits by canning is a patriotic duty. The war makes the need for food conservation more imperative than at any time in history. America is mainly responsible for the food supply of the world. In this way the abundance of the summer may be made to supply the needs of the winter. By the modern cold-pack method it is as easy to can vegetables as to can fruits. Some authorities say it is easier. At any rate, it is more useful. In the cold-pack method of canning, sterilization does away with the danger of spoilage by fermentation or "working." Sterilization consists in raising the temperature of the filled jar or can to a germ-killing point and holding it there until bacterial life is destroyed. The word "container" is used to designate either the tin can or the glass jar. Single-period cold-pack canning, as distinguished from old-fashioned preserving, offers a saving in time, labor, and expense, and satisfactory results. As the foodstuffs are placed in the containers before sterilization, they are cold and may be handled quickly and easily. Then the sterilization period is frequently short. This is time-saving. Finally, no rich preservatives, such as thick syrups or heavily spiced solutions, are required. Fruits may be put up in thin syrups. Vegetables require only salt for flavoring and water to fill the container. Another advantage of this method is that it is practicable to put up food in small quantities. It pays to put up even a single container. Thus, when there is a small surplus of some garden crop, or something left over from the order from the grocer's, one can take the short time necessary to place this food in a container and store it for future use. This is true household efficiency--the kind which, if practiced on a national scale, will conserve our war food supply and will, after the war, cut heavily into the high cost of living. There are five principal methods of canning: (1) the cold-pack, single-period method; (2) the intermittent, or fractional sterilization method; (3) the cold-water method; (4) the open kettle or hot-pack method; and (5) the vacuum-seal method. Of these the one worked out on scientific lines by leading experts and used by many commercial canners is so much the best method for home canning, because of its simplicity and effectiveness, that it is recommended by the National Emergency Food Commission and the details are explained in their manual.