Chinese seal materials are full of varieties, including metal, bone, jade, bamboo and pyrophyllite. Before the Ming dynasty, seals were made for practical purposes, and generally were made of copper, jade and ivory. Most were made of copper, hence came ‘the age of copper seals’. After the Ming dynasty, with the rise of literati seal carving, stone seal materials cheap in price, soft in texture and easy to carve, were introduced to the field of seal carving and became the main material, forming ‘the age of stones seals’ in the development of seal history. The main material used for stone seal carving in the Ming and Qing dynasties was pyrophyllite. This kind of material with a soft and delicate texture, and a rich and mild lustre, is highly expressive on engraving with high ornamental value and is the preferred material for carving seals. Qingtian Stone, Shoushan Stone and Changhua Stone are among the most prestigious ones.
The seal knob, also known as seal nose, is the part to tie with or to pinch by hand. The knobs prior to the Qin dynasty were more practical, such as nose knob, pillar knob and knob with hook. Some of them also showed decorative taste, such as pavilion knob, animal knob, and figure knob. By the Qin and Han dynasties, the turtle-shaped and nose knob became quite common. The official seals in the Sui and Tang dynasties and Northern Song and Southern Song dynasties usually had the simple and practical nose knobs, wooden knobs, and small stake knobs. But after the Song and Yuan dynasties, with the revival of private seals, the knob making also developed into some new forms, with the appearance of a variety of animal, figure shapes. Ming and Qing dynasties marked the heyday of the art of seal knobs. With the rise of carved stone seals and development of literary seal carving, people began to pay more attention to the ornamental value of the knobs, from the court to the common, thus promoting the prosperity of seal knobs production in terms of themes, techniques, and styles.