He said with emotion: "That kind of vermilion clay is genuine Zisha vermilion clay, with a vermilion red color that is brilliant yet not vulgar, suitable for making works of 'powder' red clay." Clay material was also an important basis for Gu Jingzhou's appraisal of Zisha ware. In the 1960s and 1970s, Gu Jingzhou authenticated historical masterpieces for major museums across the country. When analyzing works by Shi Dabin from the Ming Dynasty, he wrote in related articles: > (1) The Zisha clay used by Shi Dabin was carefully selected for purity and processed with meticulous care, transforming the coarse quality of early pottery that resembled jar and urn materials. (2) He emphasized the blending of clay material colors and paid attention to the lustrous surface effect after firing. Therefore, he mixed relatively coarse and uniform particles into fine powder material, the so-called "mixed with sandy steel clay," which created an effect that was elegant, firm, and wonderfully indescribable. It can be said that Gu Jingzhou's understanding and application of clay materials exceeded the knowledge structure possessed by ordinary Zisha artisans. He established a series of strict technical standards for clay materials, from material selection, clay preparation, and beating clay strips and slabs to forming the body cylinder. He maintained an extremely rigorous scientific attitude regarding material specifications and processing intensity, which not only made the production process flow seamlessly with coherent rhythm and spirit, but also gave his works harmonious and elegant color tones. They expressed the subtlety of Eastern aesthetics and the enduring literati atmosphere, complementing the simple forms, ultimately forming an artistic style that was archaic and simple, dignified and generous. --- [1] Gao Yingzi, *Master of Chinese Arts and Crafts: Gu Jingzhou* (Nanjing: Jiangsu Fine Arts Publishing House, July 2010), p. 52. [2] Gu Jingzhou, "An Overview of Yixing Zisha Teapot Art," in *Zisha Through the Ages*, ed. Shi Jundang and Sheng Pansong (Shanghai: Wenhui Publishing House, October 1991), p. 176.