17. Handles, spouts, figures in relief, and other additions of this nature, are separately made in moulds, and stuck on the vessel with the same kind of materials, sometimes mingled with a small proportion of plaster of Paris. These appendages are added after the vessels have become partially solid in the air. 18. _Burning._--All vessels, even after they have been dried in the atmosphere, are in a very frangible state; and, to render them sufficiently firm for use, they are submitted to the process of burning in a kiln. To preserve the ware from injury while enduring the fire, the several pieces are enclosed in cylindrical boxes called _saggers_, which are made of baked clay. These boxes are placed one above another around the sides of the kiln, which is of a circular form, and gradually tapering to the top. 19. In burning the coarser wares, every piece is not thus inclosed; but, between every two saggers, a naked piece is placed. A moderate fire is first raised, which is gradually increased, until the contents of the kiln are brought to a red heat. The burning occupies between twenty-four and forty-eight hours. All wares, except the coarsest kinds, are twice, and sometimes thrice, burned; and, after having been once submitted to the process, they are said to be in a state of _biscuit_. 20. _Painting and printing._--When the vessels are to be ornamented with colors, it is necessary, in most cases, that this part of the work be done after the first burning. In China, and at the porcelain manufactory in Philadelphia, the drawings are executed by hand with a pencil. The same method is used in Europe in elaborate pieces of workmanship. But, in the common figured wares, where but one color is used, the designs are first engraved on metallic plates, and impressions are taken from them on thin paper, by means of a copperplate printing-press. 21. In transferring to vessels designs thus produced, the paper, while in a damp state, is applied closely to the surface of the biscuit, and rubbed on with a piece of flannel. The porosity of the earthen material causes the immediate absorption of the coloring matter, which, in all cases, is some metallic oxyde. For a blue color, the oxyde of cobalt is used; and for a black, those of manganese and iron. The paper is washed from the ware with a sponge. 22. _Glazing._--To prevent the penetration of fluids, and to improve the appearance of the ware, a superficial vitreous coating is necessary. This can be produced by the aid of various substances; but, in a majority of cases, red lead is the basis of the mixture employed for this purpose. Equal parts of ground flints and red lead are used for the common cream-colored wares. These materials are mixed with, and suspended in, water, and each piece is dipped in the liquid. The moisture is soon absorbed by the clay, leaving the glazing particles on the surface, which, in the burning that follows, is converted into a uniform and durable vitreous coating.