PROCESSES or MANUFACTURE. Porcelain is made by firing together two natural materials which are known by Chinese names, kaolin and petuntze, al though the deposits found in Europe are not com monly of exactly the same chemical nature as the Chinese. The latest careful writer on the subject, William Burton, says expressly that the kaolin has been produced by the gradual decomposition of the petuntze: and it is admitted that the two natural substances, the harder and more rock-like petuntze and the elay-like kaolin, are of the same general composition. The body is generally made of the kaolin just as any piece of pottery is modeled in common clay, and the fusible petuntze forms the glaze, but with this peculiarity in the process, that body and glaze are fired together. This is exceptional in the ceramic art, because in most varieties of pottery the glaze is applied separately and fired separately and at a much lower temperature. The temperature needed for the firing of true porcelain is about 1400° Centi grade, or more than 3000° Fahrenheit. The few pigments that will bear this great heat are ap plied on the body and under the glaze. Paintings in vivid colors are nearly always of the nature of enamel applied upon the glaze and showing plainly as in slight relief, or else as having a surface altogether different from that of the glaze, and usually much less brilliant.
BIBLIOGRAPHY. Treatises on porcelain are Bibliography. Treatises on porcelain are usually to be found in the books devoted to ceramic ware in general. (See the bibliography of
POTTERY.) A few have been devoted to this spe cial ware, and the most celebrated of these is the work of Jacquemart and Le Blant, Ilistoire artis tique, industrielle et eommercialc de la porce /able (Paris, 1862). This work has been in part superseded by more recent treatises, but is famed for the admirable illustrations from etched plates by Jules Jacquemart. Chinese porcelain has been treated in two French books, La ceramigue chi -noise, by Grandidier ( Paris, 1894), and La poree laine de Chinc,by 0. Du Sartel (ib., 1881) ; these works are large quartos with many plates. The work devoted to the Walther collection in Baltimore, whose chief author is Doctor Steven W. Bushell, contains a more profound study of the subject than any other work, and its illustrations are admirable chromolithographs. The same distinguished expert has aided in the publication of A. History and Description of Chinese Porcelain, by Cosmo Monkhouse (New York, u.d.. about 1901), The publications con nected with the Sevres manufactory are impor tant, especially La manufacture national(' de Sevres, exposition universelle de 1900, having a carefully prepared text, and a number of excel lent plates illustrating the most recent produc tions. _1 History and Description of English Porcelain, by William Burton (New York, n.d., preface dated 1902), is a really critical treatise, as is also the popular treatise by Lehnert, Das Porzellan (Bielefeld, 1902).