=119. Insulation of Refrigerators.= The more complete the insulation of a refrigerator, the more efficient it will be. Different kinds of material, as well as dead-air spaces, are used for this purpose. The top, as well as the bottom, must be insulated. Materials which are likely to crack or settle down and leave uninsulated spaces should not be used. Because sawdust settles, it is not satisfactory. There are felts, papers and other materials which are good. If the refrigerator is not water-tight and the insulating material absorbs water, it will lose its efficiency for insulation. =120. Circulation in Refrigerators.= The better the circulation in a refrigerator, the more efficient it will be. The air in the refrigerator must be free to circulate over the ice. As it cools, it should drop to the bottom of the ice box. When it warms, it will rise and be displaced by fresh falling cold air. It should be free to rise to the top of the refrigerator and from there pass into the ice chamber and over the ice to be cooled again (Fig. 57). When the ice always melts unevenly and in the same relative place--that is, more on the side or bottom--it indicates poor circulation in the refrigerator. =121. Drip from Melting Ice.= There should be a pan under the ice to catch the drip from the melting ice, and a drip pipe to carry it out of the refrigerator (Fig. 57). If the drip pipe passes into a pan set under the refrigerator, the pan should be emptied so that it will not overflow. The water in the pan should not be allowed to become stagnant. If this pipe passes to a drain, it should not be attached to the drain, but drip into it. The small amount of fresh air passing up the drip pipe from the room is advantageous. Because some air does flow thru here, the drip pipe and the drain pipe must be clean and free from gases and odors. The drip pipe should be straight and free from places in which dirt may collect. It must be removable, so that it can be cleaned. The doors of the refrigerator must shut so tightly that frost or dew will not form about their edges on a hot day. =122. Arrangement of Food in the Ice Box.= Ice boxes are usually cooler at the bottom than at the top. Do not put food in the ice chamber because this necessitates opening the door and wastes ice. Do not put papers or flat boxes on the shelves which will interfere with the circulation of air in the refrigerator.