DRYING.
If the brick are to be dried in the open air, the nature of the clay should be studied so that the current of air admitted to the drying apartment will not be sufficient to crack, warp, or in other way injure the green brick. If the brick are to be dried by artificial means the method employed will depend largely upon local circumstances. If an abundance of fuel can be obtained near by, and at low cost, it may in some instances be cheaper to place the moulded brick upon cars suitably built of iron, and have them conveyed to a drying tunnel, at one end of which there is a furnace, and at the opposite end a chimney or stack, in which case the brick will be dried by coming in actual cantact with the flame and heat of the furnace. In some cases these drying furnaces are so constructed as to utilize the heat derived from kilns of brick in process of burning, and from which the water-smoke or steam has been previously driven off.
In all such methods of rapid drying, care should be observed that the surfaces of the brick are not dried so rapidly as to cause the shrinkage of these surfaces, and hence the cracking, which greatly disfigures the appearance of the brick and lowers their commercial value.
A large number of works manufacturing brick by the dry clay process use steam for drying purposes, the steam-pipes being so located in the drying chamber as to give a uniform temperature throughout, exhaust steam being utilized for dry ing the brick during the day, and live steam being employed at night. Where steam is used for drying the brick it is essen tial that the drying apartment should be provided with ade quate means of ventilation, in order that the moisture generated from the brick may be carried off as rapidly as possible.