How it began
Cai Lun was a court official and chief eunuch under Emperor Hedi of the Eastern Han dynasty, and headed the palace workshop that made instruments and furnishings for the imperial household. About the year 105 he conceived the idea of forming sheets of paper from the macerated bark of trees, hemp waste, old rags and fishnets, and reported the process to the emperor, who commended him. Archaeological finds show that earlier forms of paper existed in China from the 3rd century BCE, so scholars now describe his work as a decisive improvement to an ongoing process and not a sudden invention.
Before it existed
Chinese documents were written mainly on strips of bamboo and wood, which were heavy, awkward to store and difficult to write on. Silk and cloth were used as lighter alternatives, but they were too expensive for widespread use. The Hou Hanshu, the history that records Cai Lun's report, states the problem directly: silk was costly and bamboo was heavy, so neither was convenient.
How it works
The raw materials were boiled to a pulp, and the pulp was beaten with a wood or stone mallet and mixed with a large amount of water. The mixture was then lifted on wooden sieves so that the excess water drained away, leaving a thin mat of fibers. Once the mat dried it was a finished sheet of paper. The basic principles of this process have changed little over time.
How it spread
Cai Lun's apprentice Zuo Bo made important improvements to the process, and it was rapidly adopted throughout China. The resulting sheets were known as the paper of Lord Cai. From China the craft eventually spread to the rest of the world. A Japanese image of the Three Gods of Papermaking shows Cai Lun beside the Korean monk Damjing, who is credited with bringing the art to Japan.
What changed first
The new paper was found to be superior in writing quality to cloth made of pure silk, the principal writing surface of the time, and it was much less expensive to produce from more abundant materials. It quickly displaced bamboo and wooden slips. Cai Lun received wealth and fame, and was named a marquess in 114.
What lasted
Papermaking is counted among China's Four Great Inventions, with the compass, gunpowder and printing, and Cai Lun is the only early figure among their originators whose name is known. In China he was deified as the god of papermaking and became a patron of papermakers, whose mills and shops in China and Japan displayed his image. His hometown of Leiyang remains an active center of paper production.
