During ordinary cooking there is a great loss of heat, due to radiation from the cooking utensil and escaping steam. If, however, this heat could be retained, the food would continue to cook in the absence of fire. This is what occurs in the hay-box. Hay, being a poor conductor of heat, will, if closely packed around a kettle of boiling food, maintain, for a number of hours, a sufficiently high temperature to continue the cooking process. The familiar practice of using newspapers or carpet in keeping ice from melting depends upon the same principle. In both cases a material which is a poor conductor of heat, when interposed between the surrounding air and articles which are either colder or hotter than the air, being found to preserve their temperature. Other materials than hay or papers will act in the same way; such, for instance, as excelsior, sawdust, wool, mineral wool, and others. A vacuum will have the same effect as insulating materials. The “Thermos Bottle” and similar inventions, which are glass bottles surrounded by a vacuum and contained in metal cases, will keep foods hot or cold for many hours. If heated with a little boiling water before boiling food is poured in they will even cook some foods satisfactorily. A vacuum is expensive, as it is difficult to obtain, and therefore the ordinary fireless cooker is better suited to every-day use; but if one of these bottles is at hand it may be utilized in cases of illness or on journeys or in other unusual circumstances, when a cooker is not available.
The general trend of recent scientific investigation seems to indicate more and more clearly that the prevalent idea that all food must be cooked at a high temperature, such as that of boiling water (212 degrees Fahrenheit), is a mistaken one. Experiments have shown that starches are made thoroughly digestible at temperatures varying from 149 degrees to 185 degrees Fahrenheit. Cellulose, the woody fibre of vegetable foods, becomes perfectly softened at a temperature considerably below 212 degrees, while albuminous materials, of which all animal and many vegetable foods are largely composed, are not only well-cooked at a low temperature, but are decidedly more easily digestible than when cooked at the higher temperatures of boiling or baking.
SPECIAL ADVANTAGES OF THE FIRELESS COOKER
First, its economy, not only of fuel and of space on the stove, but of effort, of utensils, and also of food materials and flavour. It has been stated that 90 per cent. of the fuel used in ordinary cooking will be saved by the hay-box. This percentage will vary with different housekeepers, as some understand the economy of fuel much better than others, but there is no doubt that it is very great when the cooker is used. This is especially true when the fuel is gas, kerosene, gasolene, or denatured alcohol (possibly the coming fuel for common use). Where a wood fire or, particularly, where a coal fire must be maintained, the fuel saved by the cooker will manifestly be less than with such fuels as can be readily extinguished when their use is over, but even in such cases there is some economy of fuel. One must use the cooker to realize the saving in work that it means. Think what it is to have a method of cooking involving no necessity for remaining in the kitchen to keep up a fire or watch the food! As most hay-box cooking takes a considerable length of time, and many articles are not specially injured by overcooking, this means that foods can often be placed in the box and left for hours, while the housekeeper is enabled to go out for a day’s work, or to occupy her time in other ways, with a mind free from all care of the meal that is cooking. The user of a hay-box will soon find, too, that utensils are not so hard to wash after lying in hay as when food has been dried or burned on, and as the scraping and scouring given to ordinary utensils wears them out very fast, there is here also a considerable economy of utensils. There is found to be a very great saving of food materials on account of “left-over” foods and others that might be utilized, if the long cooking which they require to make them palatable did not involve such expense in the way of fuel as to offset the advantage of using them, such as in the case of soup stock, tougher cuts of meat, etc. Special attention is paid in this book to the preparation of a variety of cheap foods and “left-overs.”
The absence of heat and odours in the kitchen is another of the advantages of this cookery. On the hottest summer days a cooker will not increase the heat of the room, while even in a living-room, onions, turnips, cabbage, and such ill-smelling foods could be cooked with no suspicion of the fact on the part of the family or visitors. The fact that a cooker can also be made attractive in appearance, and used in rooms not ordinarily used for cooking, is of interest to some people who are not able to command even the ordinary amenities of housekeeping life.
In the matter of flavour there is a distinct gain in fireless cookery. Many are familiar, by experience or hearsay, with the specially delicious flavour of food cooked in primitive ways, such as burying the saucepan in a hole in the ground, of clambakes, or of cooking food by dropping heated stones into the mixture, in which cases the closely covered food is slowly cooked at a low temperature. The praises given to such cookery are often ascribed to the “hunger-sauce” that usually accompanies outdoor cookery, but not with entire justice, for there is a real difference in flavour.
As it has been well proved that tasteless food is less easily or thoroughly digested than food which has a good flavour, owing, probably, to the fact that high-flavoured food stimulates the flow of digestive juices, the advantage lies in this respect also with hay-box food over much of the ordinary food served.
The bearing of fireless cookery upon the servant-problem might well fill a chapter by itself. Any woman who uses this device for a year can become eloquent upon this subject. When cooking no longer ties one to the kitchen, is no longer a labour that monopolizes one’s time, dishevels one’s person, and exasperates the temper, the cook may go. We shall save her wages, her food, her room, and her waste, and have more to spend in ways that bring a more satisfactory return.
DIRECTIONS FOR MAKING A HAY-BOX OR FIRELESS COOKER
The box may be an unpainted one such as can be obtained for a few cents from any store where one of suitable size and shape is used, or it may be a handsome hardwood chest, or even an old trunk. In selecting it, choose one made of sufficiently heavy boards to admit of having hinges and a hasp put on it. If it is to be used in a dining-room, or where attractive appearance is to be desired, it may be covered with chintz or denim, or a coat of paint, if not made of finished hard wood. An old ice-box, one that has a hinged lid at the top, has been utilized for this purpose with success. A barrel makes an excellent hay-box, especially for very large kettles, but the cover cannot easily be hinged and must, therefore, be weighted to hold it down tight. In size the box should be from two to five inches larger in every dimension than the kettle it contains. The kettle is, therefore, the first thing to be secured, and full directions for choosing it are given on [page 13]. The next point to consider is the packing material. When this has been chosen, the directions for packing the box, given on [page 15], will tell how much space must be allowed for insulation and, consequently, of what size the box must be. If it is so large as to admit of more insulation than that absolutely required, there is no objection, only a possible gain. If it is intended to pack the box with more than one utensil this will also have a bearing upon its size. Allow nearly, or quite, double the insulation between the utensils that is provided on the other sides, otherwise there may be difficulty in removing one utensil while the other is still cooking.