Lamps are used to burn liquid fats and mineral oils. These lamps naturally have a different construction to those used for lighting, which are constructed with the object of burning all the carbon in the oil, so that the temperature may rise as high as possible and the carbon burn at a high white heat. The lamps used in the soot black manufacture are designed to burn only as much carbon as is absolutely necessary to maintain the flame, at the same time the temperature of the flame must be kept low, so that no portion of the soot is again burnt. These lamps have flat burners and are enclosed in a sheet-iron casing provided with an air regulator, which must work very accurately, otherwise air will enter between the joints and the working of the regulator will be deceptive. So that the material to be burnt shall not be too strongly heated, which would be accompanied by great loss when mineral oil is used, the reservoir should be placed outside the iron casing which surrounds the burner. Fig. 31 shows the construction of a soot lamp. The flat burner, B, is placed in the cylindrical sheet-iron mantle, H, which is bent above at not too sharp an angle. The products of combustion are led into a chamber, K, from which they pass into the flues where the soot is deposited. The form of the upper portion of the cylinder is of importance; if this is bent at right angles, soot accumulates on the angle, and when a mass has formed it falls off, and is partly burned in the flame. If the cylinder is given a proper bend no soot is deposited in it, but it is all carried away into the soot chambers. The air regulator, S, is placed at the bottom of the cylinder; it must turn easily. The larger the slits are made by the rotation of this regulator, the more oxygen enters the flame, and the more vigorous is the combustion. A small, well-fitting door is placed in the lower part of the cylinder, through which the wick can be reached; opposite to this a glass plate is inserted, so that the flame may be observed without opening the door. The wick is raised or lowered by means of the screw, R.