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A fine 'Sky Blue'  'Jun' bowl, Song-Jin Dynasty

A fine 'Sky Blue'  'Jun' bowl, Song-Jin Dynasty

A fine ‘Sky Blue’  ‘Jun’ bowl, Song-Jin Dynasty. Photo Sotheby’s

the steep rounded sides rising to a delicately incurved rim, covered overall in an evenly applied and fine ‘sky blue’ glaze of milky lavender blue suffused with a pale crackle and draining to a mushroom tone at the rim, the glaze pooling unevenly above the unglazed neatly pared ring foot, Japanese wood box. Diameter 6 7/8 in., 17.7 cm. Estimation 40,000 — 60,000 USD

‘Jun’ ware has been much admired over the centuries by both Chinese and Western connoisseurs for the beauty of its glaze, its depth and intensity; this particular shade of sky blue being understood as the ideal color for the monochromatic version of the ware. Over the years there has been much speculation surrounding the methodology and technology of the famous glaze. Understanding how the glaze was created proved elusive until the late 1980s when it was discovered that the blue tone is not created by pigments at all but is actually an optical effect. During firing the ‘Jun’ glaze separates into light-scattering droplets of glass and when light passes through this ‘glass emulsion’, the blue spectrum of light is reflected, giving the ware its bluish hue. The thickness of the glaze is a critical factor in creating the optical blues. It has been thought that this was a consequence of multiple layers, but analyses of sectioned shards done at the kiln sites indicate that only a single layer is applied and that the depth of glaze is attributable to the thick body, as water from the glaze is absorbed by the porous biscuit resulting in a more substantial covering. 
Sotheby’s. Chinese Art through the Eye of Sakamoto Gor: Song Ceramics, New York | 16 sept. 2014, 10:00 AM