Page:Encyclopædia Britannica, Ninth Edition, v. 19.djvu/662

Rh 638 perties of a fictile material (see fig. 69). It is difficult to realize the amount of thought and labour that was spent on the production of Sevres porcelain. The chief chemists of France devoted their energies to the invention of brilliant and varied pigments which would stand the severe test of the kiln. &quot; The works of the best painters were used for reproduction among the painted decorations of the porcelain, and many artists of real talent spent their lives in painting these gaudy toys on the whole a sad waste of labour and skill. Decora- Sevres porcelain made for actual use, such as tea-sets tion - and dessert-services, are usually painted with flowers or figure-subjects, often in many tints, and enriched with gilding, but on a plain white ground. It is the purely decorative pieces, such as vases and flower-vessels, that are ornamented with the greatest splendour. They generally have panels with pictures on a white ground surrounded by frames of gold scroll-work ; the main body of the piece is covered with one deep or brilliant colour. The chief colours are gros bleu, a very dark blue ; bleu du roi, a deep ultramarine ; a brilliant turquoise blue ; a bright pink, the favourite colour of Madame Pompadour, but generally called &quot;rose Du Barry&quot;; a bright yellow, a violet, and three shades of green were also used. These brilliant colours are often further decorated with gold ; a ground with cir cular groups of gold spots scattered over it is called &quot; ceil de perdrix&quot;; other kinds of diaper were also used. The most gorgeous variety of all is the jewelled Sevres, not made till about 1780, and generally having a ground of bleu du roi or ultramarine. It is richly set with imitation jewels, chiefly turquoises, pearls, and transparent rubies, made of coloured enamel pastes, hardly to be distinguished in effect from real stones. They are set in gold, slightly modelled in actual relief, like the gilt ornaments on the richest sort of Japanese Satsuma ware. Forms. The forms of Sevres procelain are very varied, and, in spite of the great use of plaster moulds, many reproduc tions of the same design were rarely produced. Clocks, barometers, and various other objects were made of porce lain and richly decorated, and also painted panels or plaques used for furniture, always, however, with most discordant effect. Beautifully modelled statuettes in white biscuit porcelain were made by some of the ablest sculptors of the 18th century; these usually have pedestals elabo rately gilt and painted. Perhaps the worst taste of all is shown in some of the vases which have scrolls and sham metal-work moulded and gilded to produce the effect of a porcelain vase set in or moulu mounts, a method of so-called decoration which was much imitated at Chelsea and other porcelain works. The recent &quot;Jones bequest &quot; to the South Kensington Museum contains a large variety of the most costly specimens of the p&te tendre of Sevres. Modern Processes of Porcelain -making at Sevres. Since the Franco-Prussian war a large new building has been constructed for this manufacture, with improved kilns, arranged in the most com modious way. It is near the Seine, at the entrance to the park of Saint Cloud. In the same building is the important Ceramic Museum, which contains the finest collection of French porcelain of all periods, and also a large series of showrooms for the exhibition of the modern productions of the manufactory. About 250 hands (men and women) are employed in the work ; many of the painters and modellers are, as of old, artists of real ability. Mixing The pdte dare, now mainly used, is composed of kaolinic clay, and mostly from Limousin, but also imported from Cornwall ; with it mould- is mixed a proportion of white chalk and fine sand (silica). Each ing the material is finely ground between mill-stones, and carefully washed paste. by being agitated with water. The powder is allowed to settle, and the lighter impurities are carried off by decantation. The various ingredients are then mixed thoroughly together with enough water to bring them to the consistence of cream. When the mixing process is complete the cream-like fluid is run off into absorbent plaster troughs, which take up the superfluous water and leave the compound in a pasty state. The paste is next turned over fre quently on a floor so as to expose the whole of it to the air, and it [PORCELAIN. is thoroughly kneaded like baker s dough by men s feet and hands to make it more plastic for the wheel or mould. The wheel turned by the thrower s foot is exactly like that used in Egypt under the Ptolemies, or by the majolica potters, as shown in fig. 55. While moulding his vessel the thrower keeps dipping his hands into a basin of fluid paste (&quot;barbotine&quot; or slip). He also increases the smoothness of surface on the revolving vessel by holding a sponge soaked in the slip between his lingers. Vessels of which a number are required all exactly alike, such as a set of plates, are partly shaped in a mould and partly formed by a steel &quot; template &quot; or gauge. The thrower forces a thin disk of paste over a convex mould shaped to give the inside of the plate ; he then sets it, mould and all, on the revolving wheel, and a steel knife-like gauge shuts down upon it, thus forming the outside or back of the plate, which, as it revolves against the edge, has all superfluous paste scraped from it and is accurately formed into the required shape. When the plate or other vessel has been shaped it is allowed to dry, and is finished by being turned on a lathe and rubbed smooth with sand-paper. The handles and all projecting ornaments are moulded, or rather cast, by pouring the paste in a fluid state into piece-moulds made of plaster of Paris, which take to pieces and set free the casting, which is then fixed on the vessel it belongs to with a little more fluid slip used as a &quot;lute.&quot; The moulded ornaments are afterwards carefully finished by hand with ordinary modelling tools. Even statuettes and groups of figures are cast and finished in this way. The vase with its attached ornaments, after being thoroughly dried, is ready for the first firing. The kilns are like tall circular towers tapering towards the top, Finn,! about 10 feet in diameter at the base inside ; they are divided into four stories, with perforated brick vaults between them. The fire, fed either with white wood or coke, is in the lowest story ; the chamber next to the fire is of course the hottest, and the top one the least hot of the three. These different degrees of heat are utilized according to the temperature required for each firing. Thus the &quot; raw &quot; vessels fresh from the wheel, which only require a moderate heat to prepare them for being glazed, are piled in the highest chamber, and those that are being glazed in the lowest. In order to keep the white paste from being discoloured by the smoke the porcelain is packed in round porcelain boxes (called in English &quot;saggers&quot;), which fit closely one upon another and are arranged in high piles. The various chambers of the kilns have small openings, closed with transparent talc, through which the progress of the baking can be watched, and test-bits of porcelain painted with carmine, a colour that changes tint according to the heat it is subjected to, are withdrawn from time to time to show what temperature has been reached. As a rule the fire is kept up for about thirty-six hours, and the kiln with its contents is allowed from four to six days to cool before being opened. After the first firing the porcelain is in the biscuit state, and is Glazi then ready for the glaze, which is made of felspar and quartz crystals and &amp;lt; (pure silica) ; it is finely ground with water, and the porcelain is corat dipped into it, until sufficient of the fluid mixture adheres to the absorbent biscuit to form a coat of glaze. When dry it is fired for the second time, but in the lowest and hottest compartment of the kiln, this natural rock-glaze being very infusible. About 1600 C. is the usual temperature for this process. The painted decoration is always applied over the glaze ; but within recent years a new method of under-glaze ornament has been much used, called &quot;pate sur pate,&quot; similar in method to the &quot;slip decoration &quot; mentioned above under several different heads. The biscuit ground of the vase is first tinted a uniform colour, and then the same white paste of which the porcelain is made is mixed with water and applied in successive layers with a brush, thus pro ducing delicate cameo-like reliefs. Very beautiful designs of figure- subjects or flowers are put on in this way, and additional effect is gained by the coloured ground shining through the thinner parts of the semi-transparent white reliefs. The whole is then glazed in the usual way. To return to the painted porcelain, when it has come from the second firing in a white highly glazed state it is ready for the painter. Almost endless varieties of coloured pigments are gained by the use of elaborately prepared chemical compounds, all different salts of metals. In the main the blues are from cobalt, the turquoise colour from copper, the rose-pink from gold, the green from chrome and copper, and the violets from manganese. A far greater variety and brilliance of colour can be gained in over-glaze painting than in under-glaze pigments. But the over-glaze colours are very inferior in softness and decorative beauty, and are fre quently very harsh and gaudy. Different pigments require differ ent temperatures, and three distinct firings are used at Sevres for the painting only: they are called &quot;grand feu,&quot; &quot; demi-grand feu,&quot; and &quot; feu de moufle.&quot; Pure gold for the gilt parts in a very finely divided state is- obtained by chemical solution and precipitation. The gold requires a special kiln, and firing at a higher temperature than the colour-pigments, and therefore, in the case of pdte dure, is applied first. The colours have to be put on and fired in order according to the degree of heat they require, thus very much add ing to the painter s difficulties, which are also increased by the