Cai Lun

Cai Lun (born 62? ce, Guiyang [now Leiyang, in present-day Hunan province], China—died 121, China) was a Chinese court official who is traditionally credited with the invention of paper.

Court career and invention of paper

Cai was a eunuch who entered the service of the imperial palace in 75 ce and was made chief eunuch under the emperor Hedi (reigned 88–105/106) of the Dong (Eastern) Han dynasty in the year 89.

Cai’s responsibilities extended well beyond ceremonial attendance. He began his career as a chamberlain assisting Emperor Ming before serving as an imperial messenger under Emperor Zhang. Under Emperor Hedi he held the post of prefect of the palace workshop, a position that put him in charge of producing weapons, instruments, and furnishings for the imperial household. Cai also served as a counselor to the emperor Hedi on matters of state.

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After Emperor Hedi’s death and the brief reign of the infant emperor Shang, the dowager empress Deng assumed control of the court and retained Cai as a trusted associate. In 110 she assembled more than a hundred scholars to produce a definitive edition of the Wujing (“Five Classics”)—the foundational texts of the Confucian canon—and appointed Cai to oversee the project.

About the year 105 Cai conceived the idea of forming sheets of paper from the macerated bark of trees, hemp waste, old rags, and fishnets. The paper thus obtained was found to be superior in writing quality to cloth made of pure silk (the principal writing surface of the time), as well as being much less expensive to produce and having more abundant sources.

Cai reported his discovery to the emperor, who commended him for it. Important improvements were subsequently made to Cai’s papermaking process by his apprentice, Zuo Bo, and the process was rapidly adopted throughout China, from which it eventually spread to the rest of the world. Cai himself was named a marquess in 114.

Later life and death

The marquessate, however, did not protect Cai from the hazards of court politics. Throughout his career Cai had depended on the protection of whoever held power behind the throne: first Empress Dou, then, after Dou’s death, Empress Deng. That dependence carried a cost. Years earlier, on Empress Dou’s orders, Cai had interrogated one of her rivals at court, a consort named Song, who later died by suicide. Song’s grandson was the young emperor An, who ordered Cai to present himself before the ministry of justice to answer for his grandmother’s death. In response, Cai ended his life by drinking poison.

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