Refer to the very similar pair of cups in the British Museum, illustrated by S. J. Vainker, Chinese Pottery and Porcelain, New York, 1991, p. 206, no. 158. The author explains that this type of pink enamel glaze was only introduced in the last two years of the Kangxi period, applied "by blowing it through a bamboo tube covered with a fine silk gauze at one end"