The extraordinary effect of this glaze is achieved with the use of copper and arsenic to create an opaque stippled turquoise glaze. Rose Kerr in Chinese Ceramics, Porcelain of the Qing Dynasty, London, 1986, notes 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, p. 88.