The Song Imperial kilns were in two main locations: at the former capital city of Bianjing (present day Kaifeng city) during the Northern Song Dynasty, and later at the city of Hangzhou in the Southern Song Dynasty after the regime moved southward. The Northern Song Imperial kilns produced celadon, but with various shades and lustre in the glaze. The glaze colours included light greenish-blue, moon white, glossy grey and yellow-green. Though the colours were different, they all contained the common element of green or blue-green, and their beauty was heightened by the different coloured bodies. The bodies can be blackish grey, dark grey, light grey or earth yellow, and when coated in glaze, produced different greens and blues. Since the body colours were quite deep, it conveyed a sense of sophistication.
The bodies most often used for Imperial wares contained rather high concentrations of iron, producing an effect known as “purple mouth and iron feet.” At the mouth of the vessel, the glaze was thin, revealing the ground underneath and thus the purplish colour; the feet had no glaze at all, showing the iron-rich body, which turned black after being fired. Imperial porcelain also borrowed from the Ru kiln technique of decorating the porcelain with crackles, which gave the vessel extra vitality in glaze colour as well as sophistication and an antique quality. This kind of beauty occurred naturally through the glazing process, and was in accord with Song Dynasty ideologies.
Historical records describe the Imperial kilns of the Southern Song Dynasty being located at the foot of Mount Phoenix. Tons of shards from porcelain wares and kiln equipment were found at the location described, but the kilns were unknown until September 1996, when the Tiger Cave kiln was discovered by chance, at a site close to the ruins of the Southern Song Imperial city near Mount Phoenix. Among the large amounts of porcelain fragments, inscriptions in brown pigment that read “Xiuneisi” or “Imperial Kiln” were found underneath glazed porcelain fragments that formed the base parts of vessels. In an excavation by the Hangzhou Cultural Relic and Archaeology Institute that followed, more Imperial ware fragments and kiln tools were uncovered. A second Imperial kiln was built during the Southern Song Dynasty, named Jiaotan Imperial kiln. Its ruins remain today in the southern suburbs of Hangzhou City.
Imperial Guan porcelain of the Southern Song excelled in glaze colour, the crackling effect of the glaze and form of the vessels. The style was of modest simplicity, yet elegant. The glazing effect made it feel moist and smooth as jade. Minimal decorations were used. Aside from the common plant and animal motifs, there were also many types of parallel lines, the eight trigrams, cloud and thunder, geometric designs, rings, dots and so on. Techniques of decoration included engravings, mold imprints, relief, sculpturing, pierced patterns and pierced sculptures. Engraving was mostly used on bowls, dishes, and other containers for daily use. Mold imprints were widely adopted by the full range of vessels. Embossed sculptures were mostly used for vases, kettles, stoves and wine containers, which were vessels imitating ancient styles. Pierced sculpture was used to decorate lids, pedestals and stoves. With the growing number of methods of decoration and improvements in porcelain firing techniques as well as for a multitude of crafting tools, the Southern Song Imperial kilns were of the highest quality.
The Ge kilns had always been considered a mystery in the history of ceramics. Although authentic Ge wares are on display in the Beijing Palace Museum, Shanghai Museum, and the Palace Museum of Taipei and elsewhere, there is little surviving documentation from the Song Dynasty, nor have any kiln sites ever been identified. Some ancient texts mention pottery called Ge which literally means “elder brother”, because it would seem to have been made by the eldest of a family of potters in the region of Longquan . It appears that their work resembled the Guan wares of Bianjing, but the crackle in the wares was not the like the “claw marks of crabs in the sand” characteristic of Guan wares; instead they more resembled “fish eggs” in pattern.
Existing Ge ware belongs in the celadon family and includes a great variety of stoves, vases, and dishes, including tri-pod cauldrons, cauldrons with fish-shaped handles, cauldrons with glazed feet and double handles, cylindrical vases and thin-necked urns, with most imitating the designs of ritualistic bronze ware and intended for court use. It had common elements with Ru and Imperial kilns but was very different from the porcelain used by the common people.
The most distinguished feature of Ge porcelain ware is its crackling patterns. The surface of the glaze displays natural patterns such as ice-crackles, fine crackles or fish egg crackles. The areas enclosed within the cracks can vary from widely spaced pattern called “fissured ice” to speckles as small as fish eggs. The natural crackle lines also vary in width and can be filled in with different colours such as black, gold, or red. This effect is sometimes referred to as “gold and iron threads.” The crackling in the glaze is caused by differences in the degree of expansion of various components of the glaze. This was originally an imperfection in technology, but was taken advantage of by the porcelain artisans and turn into an aesthetic feature. The wares are also known to produce a pleasing, musical note when tapped.