Page:The American Cyclopædia (1879) Volume XIII.djvu/813

 POTTERY AND PORCELAIN 789 duced to the proper consistency, although it is not perfectly homogeneous ; to make it so, it is passed through a pug mill of a similar con- struction to that shown in fig. 1, except that FIG. 19. Needham and Kite's Consolidating Apparatus. it need hot have stationary knives on the in- side of the cylinder. It is received by an at- tendant and cut by a fine wire into rectangular blocks, when it is sent to the thrower or mould- er, the throwing being performed similarly to that for common stoneware. If it is made into irregular, square, or oblong articles, it is moulded by beating and rolling the mass into a sheet and then shaping it over a block. A round plate is formed on a circular block on a lathe head and moulded with, a form attached to a standard, as shown in fig. 20. A pitcher or ewer is formed on the inside of a hollow mould of plaster of Paris, fig. 21, which is the )unterpart of the outside of the vessel. This lould is usually made in two 'parts, which, liter they are each lined with a sheet of the are put together and the seams united >y pressure with the fingers. Sometimes the rare is cast in a mould in a manner similar to FIG. 20. Moulding Plate. FIG. 21. Mould for Ewer. that for casting plaster of Paris (see CASTING), in which case the paste or slip must be thin enough to flow easily. A plaster of Paris mould is used, which if dry absorbs the wa- ter rapidly, the consolidated mass sinking to the bottom. By continuing the pouring, the mould may at last be filled with the consolida- ted material. Pieces formed by moulding in plaster of Paris soon lose by standing enough water to cause them to shrink, when they may easily be taken out. About a dozen moulds are generally used by one moulder, so that by the time that number of articles are moulded the first piece will be sufficiently firm to allow of removal. The green ware is placed upon shelves that it may become sufficiently dry to be dressed and if necessary "handled," as the operation of putting on the handles is called. Each end of the handle is dipped into a thin paste of the same material and stuck on, and enough added to secure good attachment and give the proper form. Those pieces which are FIG. 22. Earthenware Kiln. thrown upon the lathe, and therefore have a circular section, after becoming sufficiently dry, are turned upon a lathe with a sharp tool, to give them a uniform surface. After turn- ing and handling, the ware is made perfectly dry in a drying room, and then baked in a kiln of the form shown in fig. 22. The fur- naces, not shown here, are sometimes con- structed on the principle of the base-burning stove. Instead of being placed in open cells made of baked slabs, as shown in fig. 18, the articles are placed in tight cases called " seg- gars." These seggars must be made of more infusible material than that of the ware itself, or they would fall down with the weight they bear. A seggar has somewhat the form of a cheese box, as shown in fig. 23, but may be either oval or circular. It has no separate cover,