Method of packing the box. This will vary somewhat with the different insulating materials used. These may be classified as:
Those into which the cooking utensil may be set without any intervening covering, among which are hay, excelsior, and paper.
Those requiring a covering material to keep them in place and to protect them from contact with the utensil, among which are wool, mineral wool, cork, sawdust, and cotton.
Figure No. 1.
Pasteboard cylinder to fit the pail.
Boxes to be filled with the first class of insulating materials are packed in the following manner:
Line the box and cover, smoothly, with one thickness of heavy paper, or several thicknesses of newspaper. This will prevent cold air from finding its way through the cracks, and dust and pieces from sifting out. Asbestos sheeting also makes a good lining. Pack in the bottom of the box a firm layer of insulating material not less than three or four inches in depth. This must raise the cooking pail to within from three to five inches of the top of the box. Set the utensil in the middle of the space allowed for it on this layer, and pack around it, very tightly, until level with the top of the kettle. When this is removed it will be found to have left a hole just large enough for it to slip into again. A little manipulation will make the rim of this pocket less ragged than at first. The cushion for boxes packed with excelsior or hay should be at least four inches thick. In packing with paper, lay first an even layer three or more inches thick of folded papers, filling the space around the kettle with soft, crumpled papers. In place of the top cushion, make a bundle of papers folded to just the right size. This can only be done when perfectly flat pail covers are used, unless a supplementary soft cushion be first laid over the pail.
The box is now ready for cooking, but if, after considerable use, the material shrinks so that the whole space is not firmly filled, a little more may be added. There should always be at least a slight pressure when the cover is closed. The paper lining described on [page 20], while not necessary to this class of boxes, is an improvement.
Figure No. 2.
Showing how to cut the cloth pieces for lining a home-made cooker.