Bi Sheng invents movable type

Everything known about the invention comes from the Dream Pool Essays, written around 1088 by the polymath official Shen Kuo, who first recalls that the printing of books from woodblocks had become usual after Feng Dao had the Five Classics printed in the 10th century. In the Qingli era, Shen writes, the commoner Bi Sheng made ‘movable blocks’: he carved each character in sticky clay, as thin as the rim of a coin, and fired it hard. An iron plate was covered with a mixture of pine resin, wax and paper ash; the types were set close together in an iron frame on the plate, the plate was warmed until the mixture softened, and a flat board pressed on the type made its surface as even as a whetstone. Two plates were used in turn, one being printed while the other was set. Common characters such as zhi and ye had more than twenty types each; unused types were labelled by rhyme group and kept in wooden cases, and rare characters could be carved and fired on the spot.

Bi Sheng did not make type of wood, Shen explains, because the grain of wood is uneven, swells when wet and sticks to the mixture, whereas clay type came away at a brush of the hand once the plate was reheated. For two or three copies the method was no simpler than carving a block, but for hundreds or thousands it was ‘marvellously quick’. After Bi Sheng's death his types passed to Shen Kuo's kinsmen, who still kept them when he wrote. Nothing else is known of Bi Sheng; a gravestone found in 1990 in Yingshan county, Hubei, has been identified as his and would date his death to 1051, while another tradition makes him a native of Hangzhou.

Movable type did not displace woodblock printing, probably because a font of so many characters was costly to make, and the carved block remained the main method of Chinese printing for centuries. Clay type may have reached the Western Xia, where a 12th-century Buddhist sutra shows its traces; the official Wang Zhen made a large set of wooden type in 1298, and in Goryeo Korea books were printed with metal type by the 13th century, the oldest surviving example being the Jikji of 1377.