TO INSULATE AN OVEN

Choose as small a portable oven as will hold the food to be cooked, since the larger the oven the larger or more numerous the stones must be to heat it. Very large stones are heavy and awkward to manage, and with their number the cost of using the oven increases. A portable oven is on the market which is about thirteen inches in each dimension. This is a good size for a family of four or five. Cut six pieces of heavy sheet asbestos, fitting one to each surface of the oven, except the door, and two to the bottom. One of the two pieces for the bottom is to go inside the oven. Place the asbestos so that it entirely covers the oven. These pieces may be tied on temporarily to hold them in place during packing. Select a box which is at least two or three inches larger in every dimension than the corresponding dimension of the oven. It should be fitted with cover and hasp just as any cooker. Lay it, while packing, with the cover opening upward. Pack in the bottom a sufficient layer of insulating material, such as is used for other cookers, to raise the oven to within a couple of inches of the top. Place the oven, lying upon its back, on this layer with the door uppermost, and opening in the same direction as the cover of the box. Pack on all sides around it till level with the door.

If desired, a facing may be made to cover the packing material, from a piece of cloth cut a few inches larger, in each direction, than the top of the box. Draw on it a square the size of the oven. In the centre of this cut a small hole to insert the blade of scissors. From this hole cut diagonally to the corners of the square. When the cloth is put in place over the packing the triangular flaps thus made may be tucked between the asbestos and the packing, while the edges of the cloth may be tucked between the packing and the sides of the box. Fit a cushion that will fill the space left at the top and nail it to the cover of the box. Face this with a piece of the sheet asbestos nailed into place. It will be well to reinforce the nail-heads with little rounds of tin, in order to prevent them from pushing through the soft asbestos. The box is then ready for use and should be stood up on end so that the cover will open like a door, and the oven will be right side up. The extra piece of asbestos may be laid in the bottom, the stones heated, and the food put in to cook.

Method of using the oven. Heat the slabs very gradually the first time that they are used. It will be best to put an asbestos mat or piece of the sheet asbestos between a hot gas flame and the stones for a few minutes, not turning the gas on full force for the first five minutes. After the first using it will be safe to heat the stones directly over the flame, providing it is not burning with full force for the first few minutes. The degree of heat in the stones will regulate the heat of the oven. For most baking, the centre of the top side of the stones should be about as hot as a flatiron for ironing. This will mean that the side toward the flame is very much hotter, perhaps red hot. Another and better test is the browning of a piece of white tissue paper laid on the centre of the stones when they are put on to heat. When this grows a shade darker than manila paper, or a golden brown, the stones are right for loaf cakes, pastry, apples, potatoes, beans, scalloped dishes, most puddings, and bread. For a hot oven the paper should be a rich brown. This is suitable for biscuits, small cakes, roasting meat, etc.

Although gas is the fuel here mentioned any other fuel will serve to heat the stones, provided a hot enough flame can be procured. The stones may, when warmed, be set directly on a hot coal or wood fire to complete the heating, and, for out-of-doors use, a crude fireplace might be built up of rough stones to support the soapstones or they may be buried directly in the hot coals. In such a case it will probably be necessary to have some device, perhaps ice-tongs, for removing the stones, as the metal handles might in time become burned off, bent, or weakened so as to be unsafe.

Small soapstone griddles or foot-warmers make excellent slabs for the home-made insulated oven. Griddles are on the market that are as small as twelve inches in diameter, and foot-warmers come in many sizes. Those measuring eight by ten inches will be about as large as most women can easily handle, since they are thicker than the griddles, and are very heavy for their size. It will not be difficult to get an extra handle fitted to these, which will make them less awkward to manage. For baking many loaves of bread and cake, and for foods to cook over night, or for many hours, more than two stones may be necessary to maintain enough heat.

The oven should not be opened during the baking, but if the food is not found to be cooked when it is opened, it may be quickly closed again, and left till the food is done. A succession of articles may be baked in an already heated oven by quickly removing the finished article and one or two stones to be reheated and tested, and slipped again into place. In this case the door of the oven should be instantly closed after removing anything from it. This method of baking a number of things in quick succession is very economical as a few minutes will reheat the already warm stones.

Lay one hot stone on the asbestos at the bottom of the oven with the hotter side down; put a wire oven shelf on this, and the food on the wire shelf. If the food will not rise higher than the top of the pan, a hot stone may be laid directly across the pan, but if this is not possible place the second wire shelf as close over the food as the cleats at the side of the oven will permit, and the stone on this shelf, also with the hot side down. In case more than one pan is to go in at once, and two stones will not supply enough heat, hot flatirons or stove lids may be used to supplement them. It is often convenient, when the oven is heated for baking one article, to put other things in to cook at the same time, even though they may not require browning. For instance: A chicken or roast may be cooking between two stones, while on top of the upper stone the giblets may be stewing in water, or some vegetables be boiling. It will be best in such cases to heat these foods till boiling before putting them in the oven, or they will cool it too much. Such foods, as do not require browning, will not need another stone on top. It may not be wise to put so much watery food in the oven when baking anything so critical as bread or loaves of cake, as it cools the oven to some extent.

No matter how carefully the directions are given and followed some experimentation will probably be required before a novice, or even an experienced cook, will feel at ease with this new method of cookery, since the conditions may be so variable. But there is no reason why a careful observation of results and their causes should not soon lead one to become mistress of her own insulated oven, and it is likely that she will then become sufficiently attached to it to justify her perseverance.

In case a cooker-pail is to be utilized for baking it will be well to surround it, on top, bottom, and sides, with the heavy sheet asbestos described for insulating the oven. A wire rack will be needed for separating the food from too direct contact with the hot stones, and some device, such, perhaps, as an inverted wire frying-basket for supporting the upper stone.

LIST OF ARTICLES REQUIRED FOR MAKING AND USING AN INSULATED OVEN