Movable type printing: from clay characters to metal type

Every newspaper page is made of thousands of characters. The solution to this difficulty was to make each character on a separate piece, assemble the pieces for a page, print, and then separate them and reuse them for the next page. This is called movable type printing, and its first known example comes from 11th-century China.

Bi Sheng’s idea

In his book “The Invention of Printing in China”, published by Columbia University Press in 1925, researcher Thomas Francis Carter translated an account by the Chinese scholar Shen Kuo. According to Carter, Shen Kuo lived from 1030 to 1093, and his book “Dream Pool Essays” contains a contemporary and detailed account of the invention. According to the American scientific organisation AAAS, the book was written around 1088.

According to Shen Kuo, during the Qingli period a commoner, Bi Sheng, made movable type. The sources date this differently. Carter places the period between 1041 and 1049, while AAAS mentions only the reign of Emperor Renzong (1022 to 1063).

How the clay characters were made

According to Shen Kuo’s account, Bi Sheng took sticky, wet clay and cut characters on it as thin as the rim of a coin. Each character was a separate piece. They were then baked in fire to harden them.

For printing, a mixture of pine resin, wax and paper ash was spread on an iron plate. An iron frame was placed on it and the characters were set close together inside it. When the frame was full, the plate was warmed near a fire so that the mixture melted slightly, and a smooth board was pressed down so that the surface of all the characters became as level as a whetstone. After printing, the plate was heated again and the characters fell off by themselves.

Shen Kuo writes that for two or three copies this method was neither simple nor quick, but for hundreds or thousands of copies it was remarkably fast. Bi Sheng worked with two plates: while one was being printed from, the characters were being set on the other. Twenty or more pieces were kept of commonly used characters, and the characters were stored in wooden compartments arranged by rhyme.

Why did Bi Sheng not use wood? According to Shen Kuo, the grain of wood is coarse in some places and fine in others, and it absorbs moisture, so the page would come out uneven. According to Carter, all experts seem to agree that clay type was not used extensively.

Wang Zhen’s wooden characters

About 270 years later, a district official named Wang Zhen showed a way around the problem of wood. Carter has also translated his account, which is included at the end of his book on agriculture and which Carter dates to 1314.

Wang Zhen first carved all the characters on a wooden board. He then sawed each character apart with a fine saw and trimmed them with a knife so that all were of the same height and size. More than 30,000 characters were made in all. To store them, he built two revolving tables about seven feet across: one held the characters in the order of the official rhyme book, and the other held the most commonly used characters. In his words, the typesetter does not have to go looking for the characters; the characters come to him.

According to Carter’s translation, his characters were ready in two years while he was serving as an official in Jingde district. As a trial, he printed the district’s official records using more than 60,000 characters, and 100 copies were produced in less than a month, just like books printed from wooden blocks. Wang Zhen also wrote that some people had cast characters in tin, but the ink did not take properly on them.

Korea’s metal characters

The next major step, cast metal characters, was taken in Korea. According to the Bibliothèque nationale de France, it holds the second volume of a book called “Jikji”, printed in 1377 in the Korean city of Cheongju with cast metal movable type. According to UNESCO, it was printed in July 1377 and is the world’s oldest surviving evidence of printing with movable metal type, although old Korean books also mention earlier metal printing. UNESCO inscribed it in its “Memory of the World” register on 4 September 2001. According to the library, the book predates the Gutenberg Bible by 78 years.

According to Carter, a government office responsible for casting type and printing books was set up in Korea in 1392, and large-scale casting began in 1403, producing several hundred thousand characters in a few months.

The lesson of this story

Carter writes that three things were important in Gutenberg’s success that were absent from the Chinese method: a mould for casting type, alphabetic type, and a printing press. Today’s digital font is also a new form of the same old idea: each character a separate unit that can be assembled and used again and again.