Page:Brinkley - China - Volume 1.djvu/420

that any influence should be ascribed to the soluble salts obtained from them; moreover certain passages that treat of glazing material seem to show that it is sometimes composed by mixing chalky earth to the felspathic quartz which forms the basis of the glazing matter. It is also explained that the mixture of caustic lime and ashes is finely ground and washed before being mixed with the petrosilex, the carbonised film which the carbonic acid of the atmosphere forms on the surface of the liquid being carefully removed to be mixed with the petrosilex. This practice has no other object than the production of a perfectly pure lime. We are apparently given to understand that it is the film of regenerated lime which constitutes the useful element, and that the fern ashes which sink to the bottom of the vessel in which the washing is effected, are thrown away as of no value. Whatever be the true action of the fern ashes, whatever be the real consequence of calcining the lime and the ferns, judging only by the rough figures which analyses give, it is evident that the presence of the lime, which enters in very minute quantities only into the glaze of European porcelain, but which, on the contrary, is found in considerable proportions in the glaze of Chinese porcelain—sometimes as much as twenty-five per cent by weight—establishes a very salient difference between the two productions."

The conclusion of this eminent expert as to the role played by lime does not seem to cover the whole ground. He truly notes that the Japanese also—who indeed acquired the art of porcelain manufacture from China—added lime to their glazing material. But he fails to note that the glazes of Japan could never bear comparison with those of China in lustre,