One should keep the following in mind in using the ordinary fireless cooker:
1. Have the food heated thoroughly before placing in the fireless cooker. (This direction does not apply to an electrical fireless cooker.) If the foods are small, as cereals, 5 minutes' boiling is usually sufficient cooking on the range; if large in size, as a piece of beef, 30 minutes is required to heat it through.
2. After heating, place the covered kettle containing the food into the cooker immediately. It is well to have the cooker near the range so as to waste but little heat while getting the food into the cooker.
3. The kettle should be well filled. A small quantity of food should not be placed in a large kettle. It is possible, however, to fill the large kettle almost full of boiling water, then rest a wire rack on the rim of the kettle and place a small pan containing the food in the wire rack. Or place the food in a pan with sloping sides and broad rim, such as a "pudding pan," which may be set in the large kettle so as to rest on the rim.
4. Do not open the cooker to "see how the food is getting along." If the box is opened, the food must be removed at once. The food may, however, be reheated and returned to the cooker. It is sometimes necessary to follow this plan, where food requires very long cooking.
5. The length of time a food must be left in the fireless cooker varies with the kind of food and style of cooker. In many of the homemade boxes, the water does not remain hot enough for cooking after 12 hours; in some, for not more than 8 hours. If foods require longer cooking than this, they should be removed and reheated as mentioned above. Food should never be allowed to become cool in a fireless cooker.
6. After using any type of fireless cooker, let the lid remain wide open for 2 or 3 hours. Except when in use do not close it tightly.
Every thrifty housekeeper should possess and use a fireless cooker. As has been mentioned, it saves fuel, prevents the strong odor of food permeating all parts of the house, lessens work and care in cooking, prevents burning and scorching, and provides workers and picnickers with warm lunches. A fireless cooker can be made satisfactorily at home with little expenditure of effort and money. It has been found that paper crumpled so as to afford considerable air space is a satisfactory non-conducting material for a fireless cooker. Detailed directions for making a fireless cooker are given in United States Department of Agriculture, Farmers' Bulletin 771, "Homemade Fireless Cookers and Their Use" and in several popular books.