What are the characteristics of official kilns in the Northern Song Dynasty?

The overall artistic characteristics of the appearance of official porcelain in the Northern Song Dynasty can be summarized as follows: the shape of the porcelain is simple and solemn, the enamel is plump and jade-like, the cracked pieces are smart and elegant, the shape is like turtle's back, the color is like eel's blood, the glaze is bright and beautiful, the porcelain mouth is slightly purple, and the bottom is brown and red as iron. The charm and simplicity of the concept of works are not only exquisite carvings and decorations, but also colorful paintings. It completely relies on the beauty of its own glaze color and fantasy pattern to achieve its aesthetic realm of pure and beautiful charm. Emperor Qianlong of the Qing Dynasty wrote a poem for the official porcelain of the Northern Song Dynasty, saying that Li Tang had been out of office for a long time, and the official kiln in Song Zhao cherished loneliness. The color is pink and green, and the veins are tattooed. It is really simple to rub the skin of eel with blood and ice, and chanting is not awkward. Whoever gives it together is lucky, and flowers are slaves. —— Gan Long Ren Yin Xinzheng Yu Ti