Open main menu

Page:Popular Science Monthly Volume 21.djvu/322

This page has been proofread, but needs to be validated.
310
THE POPULAR SCIENCE MONTHLY.

PORCELAIN AND THE ART OF ITS PRODUCTION.
By CHARLES LAUTH,

ADMINISTRATOR OF THE NATIONAL MANUFACTORY AT SÈVRES.

THE uses of porcelain have so multiplied, the employment of that material has become so general, that few persons recollect the time, not yet far back, when it was considered an object of luxury, and only delf was within the reach of all. In this paper I shall consider, first, the nature of porcelain and the history of its discovery; next, the principal points in its manufacture; and, lastly, the different methods of decorating it.

It is generally understood that porcelain is, as a rule, the resultant, of the action of fire on a certain kind of clay. No one is likely to confound it with earthenware or delf. While those wares are soft, opaque, and of impure colors, porcelain is always white, is perfectly clear, and is harder than steel. The fundamental distinction between the three wares is that earthenware is obtained by the simple action of fire on common clays; delfs are earthenwares more or less colored and glazed with a leaden enamel, which is rendered opaque by tin; while hard porcelain is obtained from a white clay, kaolin, and is enameled with feldspar.

Kaolin, a natural hydrated silicate of alumina, is absolutely refractory and opaque; it constitutes the resistant part of porcelain. Feldspars are silicates of alumina and potassa, fusible at a very high temperature into a beautiful transparent glass. If, now, we mix a quantity of feldspar with kaolin, cover the mixture with a layer of feldspar, and heat the whole at a very high temperature, the feldspar will melt and communicate to the opaque clay a clearness greater or less according to the quantity of it present, and to the superficial part of it that beautiful glaze with which all are familiar. A part of the action in this process is chemical, and consists in the production of a new crystalline silicate formed by a combination of all the substances present. The discovery of porcelain in China is traced back to a high antiquity. The Chinese have certainly made it regularly for at least a thousand years; many authors fix the discovery at fifteen hundred or eighteen hundred years ago, but no evidence exists to justify our going further back than a thousand years. The first pieces that came to Europe were probably brought by the Venetians at the end of the thirteenth century. Charles VII, King of France, received a present of Chinese porcelains, about the middle of the fifteenth century, from the Sultan of Babylon; but it was not till the sixteenth century that the importation of these Oriental products by Portuguese and Dutch merchants assumed a real importance. The discovery of tender porcelain was made in France toward the end of the seventeenth century, but