Voltage, amperage, and watt or kilowatt are the terms in common use. If you read the circulars that advertise electric cooking apparatus, you will find the request to state the voltage of your electric current in ordering a piece of apparatus. Or again, the number of watts used per hour is given, with the catalogue number and the size of an electric stove.

The cost of electricity per kilowatt (usually from ten to fifteen cents) varies in different localities.

The great advantage of electricity is that little heat is lost in radiation, and that the degree of heat is well under control. There are also no products of combustion present, and this is the only source of heat for cooking of which this is true. Both gas and kerosene vitiate the air to some extent.

=Cooking apparatus.=--The wastefulness of cooking operations, past and present, is due largely to the defects of the apparatus used. The open fireplace for wood, and the open grate for coal, are two arrangements that permit most of the heat to pa.s.s up the chimney, and into the room. See Frontispiece and Fig. 14. In Fig. 14 there is ill.u.s.trated at the right a brick oven with a flue opening into the chimney. This was one of the earliest inventions for saving fuel and heat. This oven was lined with brick or stone, and the fire of wood was built in it, and allowed to remain until it had burned out. The coals and ashes were removed, and when the brick had cooled somewhat cakes and pies were put in to bake.

This oven retained its heat for twenty-four hours, and beans put in Sat.u.r.day afternoon were taken out hot for the Sunday morning breakfast.

The method was clumsy, but a good heat saver.

[Ill.u.s.tration: FIG. 14.--A colonial fireplace. _Courtesy of the Historical Society, Ipswich, Ma.s.s._]

Figure 15 is an American stove, early nineteenth century, wood the fuel; and from this form, modified for using coal, has developed the modern American coal range (Fig. 18). Even the latest types are very wasteful of heat. Stoves like that shown in Fig. 19 have been devised for use with gas. Even with these only a small percentage of the heat generated is available for cooking.

[Ill.u.s.tration: FIG. 15.--An early American stove, 1823. _Courtesy of the Bryson Library._]

The ideal system is that which gives the largest possible percentage of its heat for cooking, and puts the degree of heat under quick control with the greatest saving of fuel, and of labor in operating. This does not mean that the stove which gives the most intense heat is the best, although some stoves seem to be constructed with that as the aim.

Let us consider some of the methods of saving heat, and study different kinds of apparatus with this knowledge in mind.

We recall the fact, first, that some substances are good conductors of heat, and others poor.[7] If you hold a metal poker in your hand, and place the other end in red hot coals, you will realize that metal is a rapid conductor of heat. If the poker has a wooden handle, the heat of the coals does not readily reach your hand, for the wood is a poor conductor.

Moreover, this good conductor is a poor holder of heat, the heat radiating rapidly from it into the surrounding air, but the poor conductor, once thoroughly heated, cools off slowly.

You can think of many ill.u.s.trations from your daily life. Why do you prefer a woolen blanket on a cool night, rather than a linen sheet, merely? Why do you use a cloth holder in ironing? What is the principle of a hot water bottle? Air is a poor conductor. Can you think of an ill.u.s.tration of this? What is the principle of a thermos bottle?

It is not difficult to see how these facts apply in our cooking apparatus.

From an oven with metal sides heat is lost by radiation. In a double oven, with an air s.p.a.ce between the inner and outer part, some heat is saved. If the outer cover is of some non-conducting material, even less radiation takes place. This is the principle of the oven devised by Mr. Edward Atkinson. Here the inner oven is of sheet iron, and the outer covering of a non-conducting material, some composition with wood pulp or paper as the basis. If in this way heat can be trapped, as it were, in an oven, it will follow that less heat will have to be supplied, and we can use a smaller amount of fuel. This is the case in the Atkinson oven (Fig. 16), where the source of heat is either a kerosene lamp, or a small Bunsen burner of the rose type, which uses only a small amount of gas.

[Ill.u.s.tration: FIG. 16.--The Atkinson cooker.]

Another ill.u.s.tration of the conserving of heat by the prevention of radiation is in the _fireless cooker_. This is a method used in Sweden in simple form, and adapted and improved to suit modern needs. Heat is supplied in the first place by gas or kerosene, and the water in the vessel containing the food is raised to the boiling point, and held there in some cases for a few minutes. The vessel is then placed in the "cooker," which is a box with thick walls of some non-conducting material, and the heat already present is sufficient to finish the cooking process, since the radiation is very slow. In some cookers a heated stone is introduced to raise the temperature slightly. Both of these devices are excellent for the long, slow cooking that seems to mellow the food material and develop the flavors that do not result from rapid cooking.

At the same time, we need rapid processes, such as broiling and toasting, which give characteristic flavors. To meet this double need, a new type of gas stove has been made. See Fig. 17.

[Ill.u.s.tration: FIG. 17.--Construction of the duplex gas range. _Courtesy of Domestic Equipment Co._]

This is a gas stove, where the oven has thick walls of a non-conducting material. The oven is heated, for a short time only, the gas flame being cut off when the oven has reached the desired temperature. At the left is an attachment where rapid cooking may be accomplished when desired, and there is a device at (1) with the same principle as the fireless cooker, or the tea "cosey." This cover is dropped over the kettle when the boiling point is reached, the flame is turned out, and the heat in the water finishes the process. There is no good reason why stoves embodying this same principle should not be used with kerosene, and with the electric current. Improved stoves of this type will be constructed, and certainly will tend toward great economy of fuel.

One method of saving fuel is by the use of a _steam cooker_, which consists of a series of compartments, one above another, containing several kinds of food, all to be cooked over the same burner, either gas or kerosene, or on one section of the top of the coal range when s.p.a.ce is being used for the wash boiler or irons.

It requires intelligence to use such devices, and those who lack it cling obstinately to hot fires and violent cooking.

_The coal range._--Progress is slow, and the coal range will not be abolished at present. Figure 18 is an example of a good range as easy to manage as possible. The coal box at (1) has a lining that prevents the iron from burning out. The air enters at (2) and pa.s.ses out at (3), when the fire is first made. When it is necessary to heat the oven, a damper is closed at (4), and the heated air then pa.s.ses around the oven in the direction of the arrows. The coal is put in at (5) and the ashes shaken down at (6). Larger ranges, resting upon the floor, have a "dump" for the ashes directly into the ash box in the cellar, and some makes have a device for operating this with the foot. The coal stove involves the labor of bringing in coal and taking out ashes, and s.p.a.ce must be given to the coal bin and ash pit. A range of this size would serve for a family of five or six. It requires from 2 to 3 hods per day. A hood should be placed above a large range, whether coal or gas.

[Ill.u.s.tration: FIG. 18.--A modern coal range. _Courtesy of Detroit Stove Works._]

=To make a coal fire.=--See that the grate is clean and that the ashes have been removed. You know that a current of air containing oxygen is needed to make the fire burn. How will you arrange the damper at (2) and (3) when you are starting the fire?

Coal does not begin to burn easily. Therefore we kindle it by materials that have a low kindling temperature, light wood, paper, and matches.

In the bottom of the grate, lay twisted pieces of paper, or very finely split pieces of wood, or shavings, next in order larger pieces of wood laid "crisscross," yet close enough not to let the coal fall through, and on the top a shovelful or two of coal. Why do you not put in flat newspapers, and lay the kindling lengthwise and solid? Put on the stove lids, arrange the dampers properly, and touch the match. Why do you use the match? Why does the match light? Perhaps your nature study lessons will help you to explain this whole kindling process.

What should be the next step in the fire making? How should you finally arrange the dampers?

A coal fire will keep well for a considerable length of time, if the coal is put on and the ash removed regularly, provided the stove is well constructed, and the coal of good quality. Add fresh coal before the fire becomes a dull red, and shows ashes. If it gets too low, wood kindling will be needed, and this is poor management. Be careful not to put in so much coal that you cannot put the lid on firmly. It ruins the top of a stove if the hot coals touch it.

Soot must be removed once in a while from the top and bottom of the oven, and from the stove pipe.

_The gas stove._--Figure 19 shows a well-constructed stove of the usual type. Notice the air s.p.a.ce, and asbestos lining around the oven. The burner for heating the oven is at (1). Holes in the sides allow the heated air to pa.s.s outside of the oven at (2) and into the oven as indicated by the arrows. The heated current pa.s.ses out of the oven at the back of the top, and pa.s.ses out of the stove at (3), where it should be carried away by a pipe into a flue. The heat of the oven burner is also used for toasting and roasting underneath, on the movable rack at (4). The oven burner is lighted by a leader burner at (5). The top burners, five in number, are at (6). Below those is a removable pan at (7). The top of the stove is removable in sections, and the burners are easily removed when cleaning is necessary.

[Ill.u.s.tration: FIG. 19.--A modern gas range. _Courtesy of Detroit Stove Works._]

The gas burner (Fig. 20) is constructed on the principle of the Bunsen burner, which you may have used in the laboratory. There is an opening in the pipe, near the stopc.o.c.k, which admits the air, that it may mix with the gas, and give the blue flame. If there is not enough air, the flame burns with a yellow color, and smokes. If there is too much air, there is a roaring sound, and the flame "pulls back" and burns with a smoky yellow flame, and disagreeable odor. There is a valve always to regulate the air supply for each burner. Figure 20 shows a burner removed from the range.

(1) is the hollow, star-shaped chamber which gives s.p.a.ce for the thorough mixing of the gas with the air. The gas enters from the connecting pipe at (2), the air at (3), and (4) is the valve for regulating the air supply.

[Ill.u.s.tration: FIG. 20.--A gas stove burner. _Courtesy of Detroit Stove Works._]

Gas ranges of this type are built in different sizes, and with varying arrangements of ovens and hot-closets. An oven above the stove is convenient. Ranges are built also for using either gas or coal. A range of the size pictured, with four large burners on the top, will serve for a family of five or six, if the work is well planned. The oven burner consumes 30 to 40 cubic feet per hour, the top burners 2 cubic feet each, and the simmering burner somewhat less. This is estimated for a burner turned on full.

=To manage a gas stove.=--Before lighting the top or oven burners see that the stopc.o.c.ks are all tight, with no escaping gas. To light the top burners, strike the match, turn on the stopc.o.c.k, and touch the match to the gas when it is flowing well. A disagreeable "popping" follows if the match is applied to the burner before the gas flows. For lighting the oven, a "leader" burner at the side of the stove acts as a taper. Open the oven doors, and the door below, strike the match, turn on the leader, and light it, turn on the back burner, and then the front burner, and _turn out_ the leader. The so-called explosion of a gas stove is due to the sudden lighting of a quant.i.ty of gas under the oven that has collected without being lighted.

The important point in managing a gas stove is to keep the stopc.o.c.k turned so that the flame is low. The full flame is needed only when water is being brought to the boiling point, and for the first heating of the oven.

The low flame should be protected from draft. Many gas stoves now have a small simmering burner that is more useful than the large burner. Another point in the use of the stove is the prevention of the "boiling over" from some kettle. The low flame helps here, and it is also necessary that the kettles should not be too full. "Boiling over" clogs the burners, and makes necessary the frequent cleaning of the pan underneath the burners.

The oven burner should be lighted from five to ten minutes before the oven is wanted, depending upon the intensity of the flames. After the food has been put in the oven, allow a few minutes, not more than five, for the food to heat through, and then turn the flame as low as possible. Often, one burner can be turned out. This you have to learn by experience. When toasting or broiling is the process, light the oven burner before using, because the work is performed by the heated iron as well as by the gas flame. Leave the lower door open, as bread toasts or meat broils, to hasten the browning process, for it is the oxygen of the air that causes the browning. Some coal ovens have a damper for admitting air for this same purpose and though some flavor is lost in this way by evaporation, the amount is negligible in a quick cooking process. The Atkinson oven is so tightly closed, that food does not acquire a rich brown in it. An opening at the top is available when a delicate brown is wanted. It is true, however, that the slow process with a minimum of evaporation gives a flavor that compensates for the brown color and flavor. All burners should be removed if the holes seem clogged and be boiled out in a solution of washing soda, two tablespoonfuls to a gallon of water. Do not blacken the burners.

_Kerosene stoves._--The best type is a blue-flame stove with a wick.

Kerosene stoves are made with no wick, the kerosene being vaporized just before it reaches the burner, but such a stove requires occasional pumping to force the kerosene into the vaporizing chamber, and on the whole is less satisfactory than the stove with the wick. The heat is intense from this blue flame, and the burner is economical of the fuel. The small kerosene stoves, burning with a yellow flame are always inclined to smoke, and difficult to keep clean. A three- or four-burner oil stove with a portable oven will do the cooking in summer for a family of five or six.

One burner consumes a gallon of oil in 15 hours. Portable double ovens are furnished with such stoves.

The kerosene stove is cheaper to operate than a gas range, even with kerosene at fourteen cents a gallon, but the heat is not under such perfect control, and the stove requires more work to keep it clean.

The one important point in the management of this blue-flame wick stove is to keep the flame down by having the wick low, and where it belongs. The cylinder around the burner prevents the escape of heat and carries it to the utensil above. A careless person, by raising the wick too high, and producing a yellow smoky flame, makes much trouble for herself. It is important to fill the tank without spilling a drop of kerosene, and to keep every part of the stove well washed off with soap and water. The wick should be rubbed off occasionally, never cut, and if an odor becomes perceptible, the burner should be taken apart and boiled in a solution of washing soda and water. The wick will need to be renewed at intervals, depending upon the amount of use that it has. With care a stove of this kind is clean and odorless.

_Electric apparatus._--Figure 21 shows a table arranged for cooking by electricity, each piece of apparatus having its own connection. Compare this with the frontispiece, the method of cooking in the eighteenth century, and you will realize how far we have progressed in the way of convenience, comfort, and heat economy. Figure 22 shows a disk stove four and a half inches in diameter, upon which a saucepan may stand, and which is therefore available for more than one purpose.

[Ill.u.s.tration: FIG. 21.--An electric cooking outfit. _Courtesy of Department of Household Science, University of Illinois._]

The advantages of electric cooking are obvious. The heat is directly conducted to each utensil, and a minimum amount is lost in radiation. The degree of heat is perfectly under control, and the manipulation is nothing more than the turning of a k.n.o.b. When the apparatus is installed, it is adjusted to the voltage, so that no further regulation is necessary.

There are no waste products, and no matches to light or throw away. If the wiring is properly done, there is no danger from fire. The one present disadvantage is the cost. Each piece of apparatus is expensive. The cost of running must depend upon the cost of electricity in the neighborhood, and the number of watts per hour used by each piece of apparatus. The larger the utensil, the more watts consumed. The disk stove in Fig. 22 uses 250 watts; a disk of 6 inches diameter, 475 watts; of 8 inches, 650 watts. Some pieces of apparatus are arranged for three different heats, with a different number of watts for each heat. With one disk stove 10 inches in diameter, 3 heats are possible, with 250, 500, and 1000 watts respectively.

[Ill.u.s.tration: FIG. 22.--A disk electric stove. _Courtesy of Landers, Frary and Clark._]

=Oven thermometers.=--A thermometer is furnished set in the door of many ranges. While these are guides after one has learned to use the oven, they are not really accurate by scale. For exact work in testing oven temperature, a hole must be bored in the side of the oven, and a chemical thermometer inserted, protected by asbestos and metal.

Simple tests for oven temperature will be found in Chapter XI.

EXERCISES