Page:Architectural Review and American Builders' Journal, Volume 1, 1869.djvu/423

 1868.] Porcelain, Glass, and Pottery. 345 from the Portuguese ; Porcellana — signi- fying a "little pig," and, afterwards, a cup. — having been applied to the cowrie shell, the inner coat of which furnished a means for the early Portuguese navi- gators to convey to their countrymen an idea of the beautiful ware of China. This is most probably the origin of the word Porcelain, though it may be, that the term was adopted and applied from the prevalent idea, encouraged by the Chinese themselves, that the material was composed of sea and egg shells, which had been buried in the earth for eighty or a hundred years.* That this was currently held is evident from the old writers. Harte says, " True fame, like Porcelain earth, for years must lay Bury'd and mixed with elemental clay." Tlie Confessor. Guido Pancerolli, quoted in Marryat's above-cited interesting work, says : " In "former ages Porcelains were never seen. "Now there are a certain mass, com- " posed of g3'psum, bruised eggs, the " shell of the marine locust, and other " substances ; and this, being well tem- " pered and thickened, is hidden under " ground, in a secret place, which the " father points out to his children ; for, " as respects others, he does not wish "them to know it. And there it re- " mains hidden for eighty 3'ears ; at the "end of which time, the children, or "grandchildren, dig it out; and when " it has been again reduced to a fluid " state, and made fit for working up, "they form of it precious vessels, very " beautiful to look at, quite transparent, " and wrought of any form, or color, " which those workmen think proper. " The remarkable virtue of these vessels " is this, that if any poisonous thing "have been put into them they imme- " diately break." The Kaolin, or Porcelain earth, is composed of our old acquaintance, silicic acid, in combination with alumina French pour-cent-anne'es, "for one hundred years." and water. Feldspar, or petro-silex, also contains the same silica and alumina, together with potash, soda and lime. Kaolin, when moulded and put into the furnace, would result in the production of an opaque mass, the ordinary pottery. The feldspar, called the flux, however, in the furnace, removes this opacity, and produces, by its dissemination through the infusible clay, a translucent mate- rial, which exhibits, under the micro- scope, both components, the flux inter- penetrating the clay. This is why we have placed Porcelain intermediate with glass — the transparent, non-crystalline silicates and the common pottery made of clay alone. The proper mixture of day and flux, when once fired or burned, is still not complete Porcelain or Ciiina. Its name, in the art, is biscuit, which requires dip- ping in the " glaze," composed of broken porcelain, Kaolin and gypsum ; and a second burning. This is the most deli- cate and important stage in the manu- facture, for the success of the product depends upon having the glaze, so com- pounded, that it will not be too fusible nor too difficult of fusion. In the first case, the glaze becomes fluid, before the paste is sufficiently baked, producing a dry, rough surface, whilst, in the last, it will not be sufficiently fluid to form a uniform surface, but will give rise to a wavy appearance. It is probable, that the ill-success of most attempts at porce- lain manufacture, in this country, have resulted from want of sufficient care in the preparation of ~the glaze. It cer- tainly cannot be due to a paucity of raw porcelain materials, whether of Kaolin or feldspar, for Chester county, of our State, and the neighboring Common- wealth of Delaware, as well as some of the New England and the Southern States, abound in extensive deposits of both these substances, of a quality ex- cellently well adapted to the purposes of the porcelain manufacturer. Their exploitation serves only to supply the demands of the producers of the com-
 * Dr. Johnson fancies the name derived from the