Bi Sheng is the inventor of movable type. (PHOTO:VCG)

    By LONG Yun

    Before the invention of printers, books had to be written by hand and then duplicated by hand in order to be mass-produced. It not only took time and was laborious, but also during the process was easy to make mistakes. With the development of the movable type, everything changed.

    The Dream Pool Essays, a Chinese classic, written by Shen Kuo who was a famous scientist in Song Dynasty, contains a detailed discussion of the printing technology of Bi Sheng's invention of movable type, which changed the way printing was done in ancient China and made printing more efficient.

    According to Shen Kuo's records, Bi's invention started from creating clay types for each of the Chinese characters, which were then hardened by fire. A square iron sheet was prepared for typesetting using a layer of resin, wax, and paper ashes mixed and spread on it. An iron frame was then used to encircle the mixture. When the frame was packed, a plate was complete and the mixture was heated until it melted. Meanwhile, a wooden board was used to press the clay types down to the height of the frame, and the plate was ready for printing. Two iron sheets were employed for improved efficiency, one for new typesetting and the other for printing, so that a new plate was ready before the previous one had produced the required number of copies.

    To prepare for the repetition of characters on the same page, there were several duplicate types for each character, and there were twenty or more types for certain common characters.

    "Bi Sheng's innovation was revolutionary for his time." Shen Kuo said that the method was arduous if only a few copies of a book were to be printed, but it was extraordinarily rapid and efficient if hundreds or thousands of copies were to be printed. However, besides his invention, little is known about Bi's  life.

    About 400 years later, Johannes Gutenberg invented a machine that used movable type in Germany.

    In the history of printing, the invention of movable type was a major technological breakthrough. It has had a tremendous impact on subsequent generations. As a printing method with a long history and heritage, it continues to generate interest.