The extraordinary effect of this glaze is achieved by applying an opaque stippled turquoise glaze coloured with copper and made opaque by mixing in arsenic as an opacifier. Rose Kerr, Chinese Ceramics, Porcelain of the Qing Dynasty 1644-1911, Victoria and Albert Museum, 1986, p. 88, explains that "while visual examination reveals there to be two distinctive types of robin's-egg glaze, one streaked with copper-red and the other stippled with blotches of turquoise and dark blue, further analysis is needed to clarify the chemistry of these glazes". This first catagory of glaze, catalogued as peacock-feather, is the much rarer of the two.
Compare with several other peacock-glazed vessels in important collections, such as the Yongzheng-marked zun from the J.M. Hu and C.P. Lin collections, illustrated by R. E. Scott, Elegant Form and Harmonious Decoration, Percival David Foundation of Chinese Art, and Sun Tree Publishing Ltd., Singapore and London, 1992, pl. 151; a Qianlong jar of 'fish basket' form is illustrated in Kangxi Yongzheng Qianlong, Qing Porcelain from the Palace Museum Collection, Forbidden City Publishing House, Hong Kong, 1989, p. 457, no. 139; and a moonflask with this glaze is illustrated in An Exhibition of Important Chinese Ceramics from the Robert Chang Collection, Christie's London, 1993, no. 48.
Compare also to the Yongzheng-marked censer from the Edward T. Chow Collection, sold at Sotheby's Hong Kong, 19 May 1981, lot 502.