A refrigerator is an artificially cooled cabinet for storage of perishable foods. Cooling occurs when the refrigerant, preferably a substance with a low boiling point, is forced to change from a liquid to a gas by the application of pressure or heat. As the liquid evaporates, it draws heat from its surroundings, thus chilling food. The gas is then caused to reliquify either by being passed outside the

cabinet to a condenser, where it is able to expand and give off heat to the surrounding air, or by gravity. This cycle operates continuously. The basic principles of both methods of refrigeration— compression and (heat) absorption—were established in the nineteenth century and applied in commercial contexts such as brewing and shipment of meat. Refrigerators on a smaller scale, suitable for household use, did not appear until the early twentieth century.

Before domestic refrigerators became available, for many households the only way to keep food cool was by storing it in a naturally cool place, such as a cellar or a larder. A more effective method was to pack blocks of ice around food. Ice became more widespread as a commercial commodity in Europe, Canada, and the United States during the nineteenth century. By 1900, department stores were stocking ice boxes, which were well-insulated wooden cabinets with one compartment for ice, another for food, and a tray to collect water when the ice began to melt. 1930s Electrolux electric refrigerator, sold in Britain through the General Electric Company .