XX The Electric Brick Oven
We had no end of experiments with brick ovens. One of the most interesting was that wherein we used the brick fireplace as an oven and did the family baking in it. On a cold morning we would build up a smart wood fire in the fireplace and enjoy it during breakfast time. Then we shovelled out the coals and the ashes, and shut it up tight with a sheet iron arrangement and utilized the heat stored in the bricks for doing all sorts of cooking.
Our outdoor brick oven and our monthly baking day were such a success that they led to the construction of another oven of smaller dimensions for the kitchen. This one was heated by electric lamps—one in each of the eight corners. It had double glass doors in front so that the cooking process might be watched. The glass of the inner door would be clouded with moisture for a while, when the cooking first began, but this would soon clear up, and then the lamps enabled us to watch the colour changes in baking, etc. The lamps in the upper part of the oven were connected with a different switch from those in the lower part of the oven, so that we were able to control the browning on top or bottom at pleasure.
Harold introduced a device for automatically controlling the temperature of this oven.
Strips of brass and iron, B and I (Fig. 177), were riveted together. These were fastened in the socket A. They are shown edgewise in the diagram. The upper end of this compound strip is free to bend back and forth in the plane of the paper, as here represented. They normally touch the screw C. One of the electric light wires runs from the lamps in the oven to this screw C. One wire of the dynamo circuit G goes to the lamps, and the other connects with A. Thus the compound strip acts as a switch to open and close the circuit upon the lamps.
This thermostat, as it is called, was placed inside of the oven. Heat causes brass to expand more than iron and therefore when the temperature reaches a certain height the thermostat curves, so as to break the contact with C, and the lamps go out. When the temperature falls a little the thermostat straightens until contact is again made with C. C is a screw and can be made to advance or recede in its socket E, so that the temperature of the oven may be maintained at any point desired. The wire of the screw C extends to the outside of the oven, where it carries an index, D, over the face of a dial, as shown in Fig. 178.
The cook may set this index at any desired degree, and the lamps will indicate when that degree has been reached. The thing to be baked is then put inside and the clock, illustrated in Fig. 175, is set so as to warn when the time is up.
The electric spark which occurs when the thermostat breaks contact with C causes the metals to corrode at that point, and corroded metals are poor conductors. This corrosion is due to the oxygen of the air. There is one metal—the expensive platinum—which is not corroded by the electric spark. We drilled small holes in the end of the screw C and in the brass strip and pounded into these holes little pieces of platinum wire. Harold said he felt like a dentist filling a tooth. This furnished good, clean contact at all times.
It takes a long time to heat up the brick oven, but it holds its heat a long time and makes an excellent fireless cooker after the lamps are turned out. It does not allow heat to escape into the kitchen, which makes it a comfort in our summer cottage. We are all becoming daft on slowly cooked food—a sort of ripening process which gives time for the chemical changes to take place and develops the finest flavours of the food.