Ruyao porcelain ranks first among the five famous kilns of the Song Dynasty – Ruyao, Guan, Ge, Ding, and Jun – named after its production in Ruzhou. It is renowned in China's Ceramic history as “Ruyao Supreme.” Ruyao porcelain boasts an archaic and generous shape, with precious agate used for glazing, giving it a unique color and the praise of “agate glaze passed down through ancient times.” Its luster changes with light, and its glaze resembles “the clear sky after rain, clouds parting,” or “thousands of peaks revealing their emerald waves”—its soil is finely textured, its body like a jade figure, its glaze thick yet its sound resonant, its brightness soft on the eyes. The surface exhibits fine hairline cracks like a cicada's wing, with characteristics described as “pear skin, crab claws, sesame flowers,” earning it the world's admiration as “resembling jade, not jade, yet surpassing jade.”

Ruyao porcelain began firing during the Tang Dynasty, flourishing in the Northern Song (between 1086-1106), specifically made for the imperial court, also known as “Imperial Ruyao.” The craftsmanship of Ruyao porcelain is exquisite, using carefully selected materials, unique formulas, and superb firing techniques. Due to the optimal reduction of iron, it surpassed all other kilns of the time, marking a groundbreaking achievement in the development of Chinese celadon.

In the late Northern Song period, due to the wars between the Song and Jin dynasties, the technique was lost. Since the Yuan Dynasty, attempts at imitation have been made throughout the ages but rarely succeeded, making it extremely precious and a rare treasure. Ruyao porcelain often bore the inscription “Fenghua” in the Northern Song Dynasty, and the capital minister Cai Jing once had his surname “Cai” carved as a mark of honor. From the Song to the Qing Dynasties, Ruyao porcelain used by the imperial court was treasured as if it were priceless, equated with the antiquities of Shang bronzes and Zhou tripods, earning the saying, “even if one has ten thousand strings of cash, a piece of Ruyao porcelain is more valuable.”

Rare contemporary imitations of Ruyao porcelain mainly fall into three categories: one category is produced by ceramic studios of Taiwanese artisans. Due to the high iron content in the local clay, these pieces often exhibit an iron-rich body similar to Ge Kiln's “purple rim and iron foot.” These Ruyao wares are relatively finely shaped, with matte surfaces and varying degrees of glossiness.

Another category is mainland imitations, which vary widely in quality and color, such as Wending, Dongdao, Yidao, Fenghua, and others. There is also a category of celadon imitating Ruyao that falls between Ge Kiln and Ruyao, such as Qingci Lanting and Imperial Appreciation Celadon. This type of porcelain has a texture between Ge Kiln and Ruyao, with non-glassy glazes and no air bubbles on the surface.

In terms of shape, imitations appear stiff and lack spirit. Especially those made by slip casting, they lack vitality even more. Imitated Ruyao tripod string vases often have excessively thick bodies. When I asked the imitators why they didn't make the bodies thinner, they replied that thin bodies are prone to deformation. It seems there are issues with the clay formula. Additionally, many fictitious shapes are created, which should be given special attention.

Regarding the glaze quality, the glaze quality of imitations is difficult to achieve complete consistency with genuine pieces, often having a milky turbidity, tending towards “Jun glaze,” with colors mostly leaning towards blue. The glaze surface either lacks crackling altogether or has excessive cracking. In terms of craftsmanship, the marks left by spurs are either too large or too small, and the color of the spur marks is often overly white.