The movable type was invented in China by a commoner named Pi Sheng during the Chi’ing-li period (1041-1048). Before this, Chinese printers relied on block printing.
Pi Sheng’s system
Pi Sheng used a system where each type was made from moistened clay into which one Chinese character was carved. The type was then put into a hot fire to harden, so that it would become more durable and suitable for use over and over again.
When it was time to print, the printer would smear an iron platew ith a mixture made from turpentine, resin, wax, and burned paper ash. The types were then placed on the plate to form the text that was to be printed, and an iron fence fastened tightly to the plate made sure that they stayed in their respective places.
When it was time to remove the types, the printer would place the iron plate with its content on a gentle fire to melt the mixture that had glued the types to the plate. Soon, a swift push of the hand would be enough to loosen the types from the plate, making them ready to be moved around to create something new.
One of the reasons why Pi Sheng used fire hardened clay instead of wood was that wood was more likely to change and distort the character carved into it. When wood was exposed to the moist printing mixture, it often became uneven and difficult to use.
For Chinese characters that were common in written texts, Pi Sheng created several types to make sure there would be enough for a whole page. It could for instance be necessary to have twenty or more types for very common characters such as “chin” and “yeh”.
Sometimes the printer would encounter the need for an unusual Chinese character and be forced to carve a new type on the spot and harden it by fire.
When an individual type was not in use, it was covered with protective paper.
Types were stored together in wooden frames. To make them easier to locate the right types when it was time to use them again, types were grouped together according to rhymes.