Bi Sheng and movable type: clay characters, composition and reuse

During the Northern Song Qingli reign, 1041–1048, Bi Sheng made clay type that could be rearranged. Shen Kuo described him as a commoner and recorded his methods of making type, composing pages and printing in the Mengxi Bitan. Woodblock printing was already established. Bi separated a page’s text into individual pieces, which could be recombined after printing.

Characters were cut into clay and hardened by firing. Each became a separate printing surface, allowing the same set of pieces to be used on different pages. Preparing a page now involved making and arranging individual characters rather than carving an entire block.

References: [1] [2]

To compose a page, the printer covered an iron plate with an adhesive mixture including pine resin, wax and paper ash. An iron frame held the arranged characters. Heating softened the mixture, and a flat board pressed the printing surfaces to the same height. The frame defined the page, the adhesive held the pieces, and leveling made even contact with the paper possible.

References: [1]

Frequently used characters needed several copies for repetitions on a page. Type was grouped by rhyme and stored in wooden compartments; missing characters could be cut and fired as required. Shen also described alternating two iron plates: while one was printing, the other was being composed, reducing delays between stages.

After printing, reheating melted the adhesive so the pieces could be removed. Storage, retrieval and recomposition became part of the workflow, giving book production a reusable set of materials and operations.

References: [1]

Shen compared small and large print runs and considered the preparation of type more efficient when many copies were produced. He also recorded that his relatives kept the pieces after Bi’s death. The Mengxi Bitan preserved the artisan’s name, materials and working sequence, leaving a distinctive account of this Northern Song technology.

References: [1] [2]