Mr. W. Burton[90] makes some interesting comments on these high–fired glazes: "There are certain technical points of great interest to be drawn from a study of the Sung productions. In the first place, they prove that the Chinese, from a very early period, had learnt to fire their pottery at a much higher temperature than the contemporary potters of the West were using.... A third point of even greater interest, which seems to have escaped the notice of every previous writer, is that the method of firing used by the Chinese naturally produced glazes in which the oxide of iron and oxide of copper were present in the lowest state of oxidisation; and this is the explanation of the seeming paradox that the green glazes, known to us as celadon, and the copper–red glazes, were amongst the earliest productions of the Chinese porcelain–makers, while in Europe they have been among the latest secrets to be acquired."
The most important feature of the Sung wares lies in their glaze, which holds la qualité maîtresse de la céramique, as an enthusiastic French writer has expressed it. Its richness, thickness, lustre, translucency, and its colour and crackle are the main criteria of the wares in the eyes of Chinese connoisseurs. Tzŭ jun (rich and unctuous), hsi ni (fine and glossy), jung (lustrous), t´ung jung (lustrous throughout or transparent) are among the phrases most constantly met in their appreciations. A word, too, is usually added on colour of the body material, which in many cases would appear to have been of a red or brown tint, iron–coloured or copper–coloured. Not that it is necessary to infer that in every instance the ware was red or brown throughout. It is a matter of observation that in many of the early wares the exposed places (usually confined to the edge of the foot rim or the unglazed base) have assumed a rusty red colour in the firing, while a flake broken from the glaze elsewhere reveals a white or greyish white porcelain body within. This will often explain the seeming inconsistency of the Chinese descriptions in which the word porcelain is applied to an apparently dark–coloured material. At the same time, it is well to remember that the Chinese words which we translate as porcelain were far more comprehensive than our own term.
Our speculations on the nature of the Ch´ai ware in a previous chapter brought us face to face with two main types of glaze, the thick opalescent glaze of pale lavender or turquoise tint, and the smooth translucent celadon glaze in which green is the dominant colour. These types are prominent on the Sung wares, and almost all the varieties of coloured Sung glazes—with such obvious exceptions as black and chocolate brown—have more or less affinity to these two. So that if we place the old turquoise[91] glaze at one end of the series and the green celadon at the other, the rest will find an intermediate place, with leanings, of course, towards one or other of the extremes. One of the puzzling features in the study of the Sung wares is the interrelation of the various makes, such as the Ju, Kuan, Ko, Lung–ch´üan, Tung ch´ing and Chün, which all appear to have had points of mutual resemblance, although the descriptions of individual specimens differ over a wide range. If, however, it can be assumed that the same fundamental principles of manufacture were observed in all these factories, and that the divergences in the wares arose from local conditions, such as variety of clays, different conditions of firing and slight variations in the composition of the glaze, a formula is established which will cover most of our difficulties. I am assured by no less an authority on glazes than Mr. W. Burton[92] that this assumption is perfectly justifiable, and that one and the same glaze might emerge from the kiln as a celadon green, a grey green, dove grey, lavender grey, or lavender turquoise under slightly varying conditions of firing, and according to the presence or absence of an infinitesimal proportion of iron or copper oxide in the body or glaze. Even with their empirical methods the old Chinese potters must have soon discovered the conditions which favoured certain results, but in the meantime quite a number of apparently different wares would have emerged from the same factory, and yet, in spite of local peculiarities, a general relationship might be observed in productions of different districts. So that when one Chinese writer compares the Ju ware to the Ch´ai, another the Kuan to the Ju, another the Ko to the Kuan, and another the Lung–ch´üan to the Ko, it is not necessary to assume that these porcelains were all grass–green celadons because we happen to know that that colour was the prevailing tint of the Lung–ch´üan ware. The Ch´ai and the Lung–ch´üan may have been as far apart as lavender and celadon green, and the chain of relationship linked up by the Chinese writers still hold firm.
Plate 15.—Sung Wares.
Fig. 1.—Peach–shaped Water Vessel, dark–coloured biscuit, smooth greenish grey glaze. (?) Ju or Kuan ware. Length 5 1/4 inches. Eumorfopoulos Collection.
Figs. 2 and 3.—Shallow Cup with flanged handle, and covered box, opalescent grey glaze. Kuan or Chün wares. Length of cup 7 1/2 inches. Diameter of box 6 1/16 inches.
Rothenstein Collection.
No one but an experienced potter can speak with confidence of the methods by which the varying colour effects in the Sung glazes were obtained, but it is quite certain that the Sung potters were not ignorant of the value of such colouring agents as the oxides of iron, copper, cobalt, and perhaps even of antimony. Green, blue, yellow, and brown glazes, which owed their tint to these minerals, had appeared some centuries before on the T´ang wares. But to what extent the men of Sung made deliberate use of these oxides is another question. It is certain, for instance, that the green celadon owed its colour to the presence of iron oxide, but whether that was a natural element in the clay of certain districts, or whether it was introduced in the glaze by the admixture of ferruginous clay, is not always clear. Again, those bursts of contrasting colour, usually red, which enrich the opalescent grey and lavender glazes, are most readily explained by the local presence of copper or iron oxide in an appreciable quantity. No doubt these effects were at first accidental, but it is certain that observation and experiment eventually taught the potters to produce them systematically. Otherwise, how explain the appearance of these colours in symmetrical splashes? The flambé glazes of the eighteenth century are known to have been produced by means of copper oxide, and it is not unreasonable to infer its presence in similar effects at an early date. But it is equally certain that many of the changing tints in the thick, uneven, bubbly glazes of the Sung and Yüan wares are due to opalescence alone. This has been proved to demonstration by Mr. Burton, who has produced from his kilns a porcelain glaze with passages of pale lavender, and even flushes of warm red, by using nothing but a thick, opalescent glaze entirely innocent of any colouring oxide.
Finally, a word of explanation is needed with regard to the frequent references to thinly potted specimens among the principal Sung wares. Almost all of the existing examples are of a thick and rather heavy type. Not that we would have them thinner, for much of their charm is due to the massive opulence of the thick opalescent glaze with its prismatic depths and changing hues. But the Chinese writers constantly refer to a thinner ware as well as the thick. Where are these thin and elegant pieces? The suggestion that, being more fragile, they have by now all perished has been coldly received as an obvious and easy answer to a difficult question. But it is reasonable enough, after all, when one remembers that upwards of a thousand years have passed since their manufacture. The alternative that they existed only in the poetical imagination of later Chinese writers is far less probable, though doubtless account must be taken of the exaggerations indulged in by men who were describing the ideal wares of a classic period. "Thin as paper," for instance, must have been a poetic licence as applied to the Ch´ai ware. I shall not cite the illustrations in the Album of Hsiang Yüan–p´ien[93] as proof of the fineness and trim regularity of the best Sung specimens. Whatever the value of this manuscript may originally have been, no reliance can be placed on the illustrations as reproduced in Porcelain of Different Dynasties.[94] The original was unfortunately destroyed by fire in 1888, and what we have now is, at best, the reproduction of a copy, and probably that of a copy of a copy. It is quite possible that the thinner Sung wares are still represented in Chinese collections, rare though they must of necessity be. But I believe that even our own collections are capable of supplying proof that, making reasonable allowance for verbal exaggeration, the Sung potters did make wares which could fairly be described as thin. Many of the white Ting wares are thin enough to be translucent; no one questions the correctness of the description as applied to them. It only wants one specimen to prove the case for the celadon glazes, and that may be seen in the beautiful bowl in Mr. Alexander's loan collection at the Victoria and Albert Museum (Plate 16). As for the Ju and Kuan ware, it is useless to consider their case until we are quite satisfied that we have established their identity; and in the nature of things the opalescent glazes and those described as "thick as massed lard" by the Chinese can only have accompanied a relatively thin body. On the other hand, many of the Corean celadons are of unimpeachable thinness, and as they were contemporary with the Sung porcelains and were almost certainly copied from them, there seems no real ground to withhold belief entirely from the Chinese statements with regard to the thinness of certain coloured Sung wares.