The modern hot-air oven suitable for enamelling and japanning here shown is about 10 ft. by 8ft. by 7 ft. high, with iron swing doors in front. An ordinary furnace Are, fire-brick lined, is built at the further end of the oven opposite to the smoke flue (see Fig. 1, which is a longitudinal section), access to this furnace fire being obtained by a flight of brick or stone steps. Ordinary furnace bars form the grating, with a cast furnace door in front. From the right-hand side at the back of the fire-box the brick flue is carried in the brick floor, as shown on plan (Fig. 2), crossing the floor three times, and then up the side wall into the smoke flue. These flues are covered with fire-brick slabs in the usual manner, forming the floor of the oven. On the left side of the back of the fire-box a similar flue is built into the back wall in a direction slanting upward; this is carried along the side wall, and thence into the smoke flue. Doors should be fixed in suitable positions for the cleaning of the flues. If more convenient to have the smoke flue in another position, it is only necessary to alter slightly the direction of the flues. The size of the furnace must depend on the size of theloven adopted.

Fig. 2. Hot-air Oven.