Gu Jingzhou Researching Teapot Artistry In 1982, during the Yixing Purple Clay Craft Factory's exhibition of new craft products at the Qianqing Palace in the Palace Museum, Gu Jingzhou was invited along with Gao Haigeng, Pan Chiping, and others to authenticate purple clay wares for the Palace Museum. Museum staff members accompanying them made detailed records of Gu Jingzhou's authentication opinions. Gu Jingzhou first proposed principled opinions on the authentication of purple clay wares from three aspects: > To authenticate purple clay wares, first one must understand the artisan's techniques—each person has their own method... Second, examine the clay color; third, look at the patterns... > The raw material for making purple clay wares is clay buried beneath rock layers, hence the saying "clay within clay." The proportion of purple clay determines the body color. > Nanjing, Yangzhou, and Shanghai each possess an authentic Dabin teapot that was excavated. Their styles and clay colors are identical, revealing that Ming dynasty purple clay had larger air bubbles and coarser body clay. Subsequently, Gu Jingzhou summarized and provided extended analysis of some important characteristics of works from various periods in the history of purple clay development: