3 oo CLAYS AND CLAY INDUSTRY. 



surface of the object to be molded. A slab of clay is laid in each 

 section and carefully pressed in, the mold put together, and all 

 seams smoothed with a wet sponge. After drying for a few 

 hours the parts of the mold are lifted off. Clocks, lamps, water 

 pitchers and similar articles are made in this manner. 



Casting. — This consists in pouring a slip of clay into a porous 

 mold, which absorbs some of the water, and causes a thin layer 

 of the clay to' adhere to the interior surface of the mold. In 

 order to produce a slip with less water, some alkaline salt is added 

 to the mixture. When the layer on the inner surface of the mold 

 is sufficiently thick, the mold is inverted and the remaining slip- 

 is poured out, the mold being removed in a few hours. This 

 method is extensively used in making thin porcelain ornaments, as 

 well as many white earthenware objects. It is also used for 

 making belleek. 



Subsequent Steps. 



Drying. — The ware after it has been molded is usually set on 

 shelves in steam-heated rooms to dry. 



From this point on, the method of manufacture varies some- 

 what, depending on the kind of ware that is to be produced. 



Burning. — Common earthenware and stoneware are usually 

 burned in round kilns, or more rarely in rectangular ones. For 

 common earthenware up-draft kilns are mostly employed, but 

 for stoneware the down-draft type predominates. The wares are 

 piled in the kiln on top of each other, and also nested whenever 

 possible. Red earthenware is not burned above cone 05, but the 

 stoneware in New Jersey is burned from cones 5 to' 8. The time 

 of burning depends partly on the size of the kiln, and partly on 

 the clay, ranging from 30 to' 90 hours. 



White earthenware and china, on account of their color, have 

 to 1 be burned in saggers, which are oval or cylindrical receptacles 

 with a flat bottom, about 20 inches in diameter and a height 

 usually of about 8 inches. 



The saggers are filled with unburned ware and set one on top 

 of the other, so that the bottom of one forms a cover for the one 

 below it, the joint between the two being closed by a strip of 



