Before the Qin Dynasty (221~210 B.C.), there were only two types of seals: the official seals and the non-official (private) seals. They were all named as Xi. When the Emperor of Qin came into power to unify China (221 ~ 210 B.C) only the imperial seal was allowed to be called Xi, while others were then named Yin. This went on until the Han period (202 B.C. ~ 208 A.D) when the rule was more relaxed. Generals of Han used to call their official seals Zhang. During the Tang Dynasty (618 - 907) , the Lady Emperor Wu Ze Tian, out of superstition, found the pronunciation of the word Xi homonymic to that of Si (which means death). She then demanded that all seal engravings be re-named Bao. Since that time, both Xi and Bao were used interchangeably.
To trace the origin of Chinese seals, one has to relate it to the discovery of the Chinese Characters. The most ancient Chinese Characters first originated in the Yin Dynasty (i.e., the later period of the Shang Dynasty, from 16th-11th Century B.C.) as inscriptions on bones or tortoise shells. Later, inscriptions were made on metals and known as Jin Wen, followed by characters on stone carvings during the Qin Dynasty.
Generally, those seal engravings that were done on metals and jade stones were called Jin Shi (meaning Golden Stones), including the then Xi seals. However, the exact origin of Xi, whether it was before or after Yin Dynasty as some historians have claimed , is still uncertain. According to Chinese history, Xi first appeared as early as the Spring And Autumn Period (Chunqiu, 770 ~ 476 B.C.), and became popular during the Warring States (Zhanguo, 475 ~ 221 B.C.).
During the Qin Dynasty, Xi was originally used as a proof for commercial trading. Its use was then extended to become a symbol of power which only imperial officials were qualified to possess. Since then, the Chinese government officials used Xi as a symbol of authority to command obedience from ordinary folks.
The picture on the right shows the different Yin Dynasty ancient seals unearthed from the Henan Province at Anyang county, the site of the older capital of the Yin Dynasty.
After the Han Period, as paper became more popular, people started to stain seal engravings with colours, and then print them onto papers. For this purpose, red ink paste was created. In ancient days, correspondences were usually written on bamboo strips. To keep the contents confidential, people would tie the bamboo strips together with strings and cover the bundle with a specially designed wooden trough sealed with mud. A symbolic seal would then be pressed against the mud to leave an identification mark. The seal engravings for this purpose had to be done with deep carvings so that the markings would be clear, whereas those meant for stamping on papers would tend to have sharp outlines. Sometimes, the seals could be so enormous in size that wooden handles had to be installed to facilitate the stamping process. This was especially so for purposes such as stamping onto horses and commodities for various transportation purposes.
Ancient seals collected over the centuries were mostly unearthed from either ruins of old cities, riverbeds or even from ancient tombs. Some were seals left behind by warriors when they went into exile, while some were found on the battle field, probably abandoned by defeated soldiers. According to the rulings then, seals confiscated from the battlefield must be handed in to the commanding officers. Even seals that were conferred by the emperor to officials for promotions purposes had to be returned when the latter left the post or upon their deaths. Other seals with personal names, official status and auspicious characters inscripted were usually unearthed from ancient tombs.
Some seals from the time of Warring States (Zhanguo, 475 ~ 221 B.C.) were even found to be engraved on ceramics and measuring instruments. Some golden coins which were believed to belong to certain dukes and princes, were also found to have names and honours inscripted together with the names of the manufacturer and their trade symbols.
From the Warring States (Zhanguo,475~221 B.C.) to the Ming (1368~1644) & Qing Dynasties (1644~1911), the main material used for seal engraving was copper. Others like gold, silver, jade, iron, crystal, agate, ivory, rhinocerous horn, magnet, amethyst, tree roots, fruit seeds, melon stems, tiles, and stones. were also used.
In the Yuan Dynasty (1279~1368), there was a legend about a famous artist named Wang Mian, who accidentally found that using a special granite stone for seal engraving gave the most satisfying results. Soon many people followed suit. Since then, intellectuals participated enthusiastically in seal engraving, and it became a social trend. As a result, the usual practice of engaging special skilled carpenters to carve seals gave way to people doing the engraving as a hobby. This further promoted seal carving as a unique art.