From the book: Kochlehrbuch fuer Schule und Haus von alma Henschel siebente Auflage 1921 Verlag B.G. Teubner Leipzig und Berlin
Translation of page 246 „Selbstkocher“ selfcookers
These are apparatuses, wherein one can ready-cook food without fire, which are before parboiled or sautéed. One saves with that much fuel and time.
Moreover the dishes stay more nourishing and more aromatic, because no matter can go out. Above that, the food stay long-time warm within these apparatus, with the advantage, that they do not need warmed up, when table-time cannot be done in time.
The cooking-box is the most simple of these apparatus; one can make them self with few labor and few cost. It is necessary a box with fast-fitting lid, best on three sides with spanning lid. It is fixed with hinges onto the box and this is stuffed with hay, wood-wool or scrap of paper. Above there must be so much space free that a pillow, filled with the same material or with plumes, has place.
Into the filling of the box one makes according to the size of it one to two or three pits, so that the cooking-pots fit into them. For the cleanness one spans a cerecloth or package-linen above, wherein holes are cut, according to the size of the pots.
The food is parboiled on a stove or on a gas- petrol or alcohol-cooker and get within the same firm closed pot, still undulating into the box. The pillow is led upon and the lid is closed, which must not be opened before time. It had to be followed that the box must not stay in a drafty place, that the food must get the needed fluid directly, but as well not too much, because it does evaporate nothing. Food which requires long cooking-time, like meat or pulse (these before soaked), must parboil 20 to 30 minutes, vegetables 10 to 15 minutes, potatoes, rice and oat groats approximate 10 minutes, semolina, sago, legumes- and oats-flour for soup or pap only 5 minutes. With some attention one finds out soon how it is best.
By cooking within the box has to be calculated approximate once more the cooking-time than by cooking on fire. But it does not matter if the food stays longer within. So the lunch-food can be parboiled directly during coffee-cooking and put into, what is very important for the in profession operating woman. In the cooking-box can only be prepared food that is to be cooked or steamed. For frying or baking there is not enough heat. After use the box must be aired and from time to time new filled. Ready for use cooking-boxes in different sizes are available in kitchen-shops.
In the same manner one can ready-cook as well parboiled food in paper-package. One puts 6 to 7 big newspaper-sheets on each other put hereon the pot with the cooking food, fold the paper quickly above and bind with a thread closely, so that there are no gaps where out the heat streams. By food with longer cooking-time, it is necessary to glue the lid with flour-paste onto the pot.
Heinzelmaennchen (Brownie) is e cooking-box, which is made for cooking, frying and baking. It is inside covered with sheet-metal, has between the sheet-metal and the outer wood-wall an isolating layer of asbestos and is equipped for one or several pots. There are added two firebricks, which are pre-warmed on the fire. For cooking only one of the firebricks gets into the box and above the pot with the parboiled food. For frying and baking the second pre-warmed firebrick gets upon, to give the top heat.
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