COOLING.
The kiln must be allowed to cool very gradually ; no aid should be given to the cooling process by opening doors or in making any channels through which the air on the outside of the kiln can enter it. The chimney must be depended upon to cool the kiln, all dampers leading to the chimney being fully open so that the stack can do this work unhampered. This should be continued until the beginning of the sixth day, when the holes in the top of the arch of the kilns can be opened, caution being first exercised that all dampers in flues leading to the chimney are closed, and that all draughts about the kiln are stopped. In this way it is possible to draw all the heat from the kiln without danger of injuring the enamel brick. The wicket, however, should not be thrown down until it is possible, when putting the hand through the holes in the top of the arch of the kiln, to pick up the brick, which must be cool enough to handle with the naked hand. By following these directions in the cooling of the brick, " air cracks" will not be inflicted upon the brick, which lessen their market value.
The sorting of the brick is usually in three classes, and has reference to the condition of the enamel surfaces of the wares. First quality brick are true in shape, have perfect corners and arrises, and the enamel surface of such brick must have neither flaws nor cracks. Brick having cracks either visible or invis ible or blisters form the second quality of wares. The third class of brick are those which cannot be sold for second, be cause they are either chipped or cracked, and the manufacturer who obtains for such brick the price of ordinary front brick is very fortunate. There is no profit in manufacturing either sec ond or third grade enamel brick. The manufacturer who can not produce at least seventy. five per cent. first-class enamel brick will find his profits absorbed.
The enamels, glazes and colors used in the manufacture of these brick can be obtained from either Messrs. Harrison & Son, Hanley, Staffordshire, England, or C. Bloor & Son, Burs lem, England.