=48. The Stones of Fireless Cookers.= The stones for fireless cookers are usually made of soapstone or some composite which will absorb considerable heat. They should be slightly smaller in diameter than the nest. They can only be used with safety in cookers which are metal-lined and insulated with material which will not ignite at a low temperature. Stones should not be put in home-made cookers which are not insulated with asbestos or other fireproof material. Hot stones can be used with safety in any of the commercial cookers which come fitted with them. [Illustration: FIG. 22. Section of fireless cooker.] The temperature in a fireless cooker is below boiling most of the time. It is, therefore, a device for simmering food, and should be used for cooking meats, fruits, vegetables and cereal dishes which require or are improved by long, slow cooking. Since the food has to be shut in a fireless cooker to keep in the heat, fireless cookery is a method of steaming of food. For this reason, it has a slightly different flavor from food baked in the oven, much as fried food differs from roasted food. Hot stones (Fig. 22) are put in most fireless cookers. The heat from these brown the food and give to the otherwise steamed food a flavor similar to that developed in baking, roasting and frying. =49. Heating the Stones.= Moisture given off by the cooking food is absorbed by the stones. They must be dried or heated very slowly to prevent this moisture from cracking them. When the stones have been removed from the cooker, wash them, because they absorb odors from the food. Keep them in some warm, dry place while they are not in use, such as in the warming oven of the cook stove or on a radiator. When wanted for use, they will then be dry enough to be placed over the gas-stove burner if it is not turned too high at first. Drying thus saves time when the stones are needed. =50. Care of the Cooker.= The cooker should be left open to air while not in use. As soon as the food and stones are removed from it, the moisture should be wiped out and the inside washed with soap and water, wiped dry and left to air. Such care is needed to prevent the cooker from taking on the odor of dishes previously cooked and transmitting some of them to those cooked later. =51. Other Devices Belonging to Cookers.= In most commercial cookers there are wire devices to raise the dishes of food from the stone (Fig. 23). This prevents scorching and boiling over when the stones are heated very hot. These devices are also used to hold a hot stone above the food to make a brown crust on it. Some cookers are furnished with valves, permitting the escape of steam when it becomes too abundant. The pressure of the steam automatically opens the valve. This device insures the cooking of certain vegetables, cereals or doughs without their becoming too soggy to be palatable (_A_, Fig. 23).