Page:Architectural Review and American Builders' Journal, Volume 1, 1869.djvu/424

 340 Sloan's Architectural Review and Builders' Journal. [Nov., moner stoneware, together with the small amount of washed and prepared claj r consumed by paper manufacturers. Fine Porcelain manufacture has failed, in the United States, from other causes than a lack of the material. Porcelain painting is done with colored, fusible glasses having the same metallic oxides for the coloring matters, as given above for glass, applied to the subject, and subsequently burnt in, in a muffle, or furnace open at both ends. Gilding is best done with finely divided metallic gold (such as the chemist pre- pares by precipitating a solution of gold by means of oxalic acid) mixed with oxide of bismuth and rubbed up with oil of turpentine, applied with a brush, and subsequently burned in, in the muffle. The clay used at the celebrated Sevres Works is obtained from St. Yrieux, near Limoges. That employed formerly at Meissen was carried to the factory, from Aue in the Erzgebirge [Ore Mountains], under circumstances of secrecy, which appear as ridiculous as the discovery of the deposit was singular. Bottcber's valet employed, in powdering his mas- ter's hair, a white substance, which had accidently been discovered by a rich iron-master of Saxony, named John Schnorr, and sold by him, in large quantities, at the fairs of Dresden, Leip- sic, and other places, for the purposes of a hair powder. Bottcher was struck with the density of the powder, found it was earthy, inquired into its origin, and, to his great joy, found, that he had dis- covered, at last, the material for the pro- duction of white porcelain ; for his pre- vious products had a red, jaspe/ous ap- pearance ; and were polished by the lapidists and gilded by the goldsmiths. The Kaolin thus singularly discovered was long known under the commercial name of Schnorrische Weisse Erde — Schnorr's White Earth. The Kaolin deposits of St. Yrieux were discovered in a no less remarkable manner ; and at first, attracted attention for the purpose of furnishing their mate- rial for a use entirely distinct from, but none the less important than, that of porcelain manufacture. The wife of a surgeon of St. Yrieux, Garnet by name, noticed the white unctuous substance, and conceived the idea, that, having excellent detei'sive qualities, it would serve as an abundant and cheap substi- tute for soap for washing purposes. The fact that numerous researches were being made, throughout France, for a supply of porcelain earth for the then newly-established works at Sevres — the success of which had been far from en- couraging — was known to the apothe- cary at Bordeaux, to whom Madame Darnet had carried the earth ; and he, at once suspecting its nature, forwarded the sample to the chemist Macquer. The discovery at once effected a remark- able change in the Ceramic Art in France ; and established the works at Sevres on a sure foundation. "' Madame Darnet, was, however, forgotten, and in misery, till the year 1825, when she ap- plied to the eminent savan, Brogniart, then at the porcelain establishment, for means of returning on foot to St. Yrieux. Louis XVIII., on being made acquainted with her circumstances, to his credit be it said, granted her a pen- sion from the Civil List. The origin of Kaolin is to be sought in what mineralogists call the feld- spathic rocks, that is, in mineral aggre- gations, which contain a large amount of feldspar as a component. The disin- tegration of this mineral is effected through the agency of the carbonic acid dissolved in all waters which, by the play of its affinities, extracts the potash, soda, and lime from the feldspar, in the form of soluble carbonates, leaving be- hind the silica and alumina combined, and in a hydrated condition, with a more or less plastic nature, as the new compound is more or less mixed (me- chanically) with undecomposed feldspar and the other mineral constituents of the parent rock. The deposit at St. Yrieux yields, not