Porcelain

by Edward Dillon

CHAPTER XVIII
THE HARD-PASTE PORCELAIN OF SÈVRES AND PARIS

THE soft paste of Sèvres, even during the period of the fifties and sixties, when the most exquisite ware was being made, seems always to have been regarded somewhat as a make-shift, to be employed until the materials for making a true porcelain should be discovered in France. For it was the ignorance of the true nature of kaolin, and where to look for it, that so fortunately delayed its introduction at Sèvres. As early as the Vincennes days, one of the Hannongs of Strassburg had offered to sell his secret, and this offer was repeated at a later time by himself and by his son. At Sèvres, before 1760, two German workmen were retained to teach the Saxon process, but the materials had still to be obtained from Germany.

Meantime Macquer, who had succeeded to the post of scientific adviser on the death of Hellot, had been experimenting on his own account, and above all encouraging others to search for the precious white earth within French territory. At length, in 1760, some samples were sent from Alençon, from which a true porcelain was made, but of poor quality and of a grey colour. Outside the Sèvres works the younger Hannong had set up a factory at Vincennes, and the Comte de Brancas Lauraguais, whom we shall meet with again in England, had by 1764 begun his experiments and his search after deposits of kaolin. There still exist a few portrait-medallions moulded in hard porcelain, which, on the ground of the letters B. L. engraved on the back, have been attributed to that energetic nobleman.

The introduction, however, of the hard-paste porcelain at Sèvres dates from the discovery, in 1768, at Saint-Yrieix, near Limoges, of those famous deposits of kaolin which have ever since that time been the main resource of the French porcelain industry.[194] Before the end of the year 1769 Macquer was able to show to the king the first samples of this new ware. The hard paste made for some years after this date was not of the ‘severe’ type adopted later on. Not only did it contain as much as 9 per cent. of lime, but, the kaolin employed being less pure, contained probably a good deal of mica—in fact, this first type of French hard paste approached in composition that of the Chinese. It is even more important to note that the glaze used at the same time was of an entirely different nature from the pure felspathic covering afterwards adopted. It was composed of Fontainebleau sand 40 per cent., potsherds of hard porcelain 48 per cent., and chalk 12 per cent. As a result, it was possible to decorate the surface with brilliant translucent enamels of some thickness.

It was the introduction of the felspathic glaze in 1780 that gave the final blow to the effective decoration of Sèvres porcelain. This glaze is made by simply fusing a natural rock (pegmatite) consisting of a mixture of potash felspar with a small quantity of quartz. The ease with which this glaze can be prepared, its hardness and uniformity of surface, led to its universal adoption not only at Sèvres but in the porcelain works of the Limoges district that have for the last hundred years supplied France with ordinary domestic wares—for such use its hardness renders it eminently suitable. But, as we have said, this combination of refractory paste and hard glaze is incompatible with any brilliancy of decorative effect, the enamel colours are quite unable to incorporate themselves with subjacent glaze, they lie dull and dead on the surface, and the faults of the German porcelain are exaggerated.

So with the paste, a much harder and more refractory type was introduced at the beginning of the next century, and (apart from the recent partial introduction of a milder type for special purposes) this type has remained in use to the present day. The lime in Brongniart’s new paste was reduced to 5 per cent., while the amount of kaolin (65 per cent.) is probably greater than in any other porcelain. There has been a reaction lately at Sèvres against this refractory ware, but the old formulas are still employed for the porcelain made for practical domestic use. When, however, brilliancy of effect and artistic decoration are aimed at, a completely new type both of paste and glaze has been in use since the year 1880, and concomitantly with the imitation of the Chinese monochrome wares, an attempt has been made to follow as closely as possible the pastes and glazes of the Chinese. M. Vogt, the present technical director at Sèvres, who has had so much to do with these changes, gives the following formula for the composition of the new porcelain: kaolin 38 per cent., felspar 38 per cent., quartz 24 per cent. The lime, it will be seen, has been completely eliminated from the paste; on the other hand, the glaze contains as much as 33 per cent. of the Craie de Bougival.

It would be a dreary task to enter with any detail into the history of the Sèvres works during the hundred years following the first introduction of the hard paste. This period is associated in most minds with the colossal vases that are to be found in so many of the palaces and museums of Europe. To judge from these examples, it would seem that the chief object both of the design and the decoration was to conceal as far as possible the nature of the material used in their composition. You have first to persuade yourself that you are looking at something made of porcelain: once convinced of this, you marvel at the technical difficulties that have been overcome in its manufacture, but what it never even occurs to one to look for in these monstrous vases, is any trace of that beauty of surface and brilliancy of decoration that we are accustomed to associate with the substance of which they are composed.

The ‘Medici Vase’ now in the Louvre is probably the earliest of this long series. This vase dates from the year 1783, and it is nearly seven feet in height. But it was in the pseudo-classical style of the empire, when encouraged by Napoleon’s love of the gigantic, and by his desire ‘à faire parler la porcelaine,’[195] that this new application of porcelain found its full expression. It is then that we find vases, candelabra, surtouts de table and clocks, in styles distinguished as Egyptian, Etruscan, Imperial, and Olympian. After this we can follow the decline of taste in the succeeding régimes till, with the total extinction of all feeling for harmony of colour and unity of composition, we are landed—in the reign of the ‘bourgeois king’—in the style or absence of style which is the French equivalent of our ‘Early Victorian.’

There is one name above all others that is associated, at Sèvres, with this long period, that of Alexandre Brongniart, who was director of the works from the year 1804 until his death in 1847. The son of a well-known architect, and himself a fellow-worker with Cuvier, he attained some distinction both as a geologist and as a chemist. It was indeed from the point of view of a man of science that he approached the subject of ceramics,—as a geologist to examine the position and stratigraphical relation of any material suitable for fictile purposes, as a chemist to analyse these materials and to discover fresh metallic combinations suitable for glazes and enamels.

It was at this time, and chiefly under the influence of Brongniart,[196] that the palette of the enameller was enlarged by the introduction of so many new colours, the employment of which gives a new cachet to the decoration of the nineteenth century. Perhaps the most important advance was in the employment of oxide of zinc in the flux, by means of which the colours of many metallic oxides are developed and sometimes altered. The green derived from chromium is essentially a nineteenth century colour, and as it resists the highest temperature this green can be used, like the cobalt blue, as an under-glaze colour. From the chromate of lead an orange-red is obtained—the rouge cornalia, a crude and dangerous colour, and one that does not withstand high temperatures. An orange-yellow from uranium, and a deep and uniform black from iridium, were also introduced at this time or not long afterwards. The ‘English pink,’ the lilac tint so extensively used in the transfer-printing of earthenware, was successfully imitated by adding a small quantity of oxide of chromium to a flux containing oxides of tin, lime, and alumina. The celadon green of Sèvres is derived, not from the protoxide of iron, but from the sesqui-oxide of chromium, with the addition of a minute quantity of copper.