Cai Lun, courtesy name Jingzhong, was a native of Guiyang Commandery. After entering the palace as a eunuch, he quickly rose from the low-ranking position of Junior Yellow Gate (a eunuch title) to Attendant at the Yellow Gate, responsible for conveying communications between the inner and outer palaces, guiding princes and nobles who sought an audience with the emperor, and arranging seating at banquets.
At that time, Emperor Zhang's harem included a Lady Song, whose son Liu Qing was originally the crown prince, but Empress Dowager Dou disliked her, so Cai Lun devised a plan for Empress Dowager Dou, forcing Lady Song to commit suicide and demoting the crown prince to Prince of Qinghe; subsequently, Empress Dowager Dou found an excuse to demote another consort, Lady Liang, to commoner status, while Lady Liang's son Liu Zhao was established as crown prince by Empress Dowager Dou and raised by her personally. In 88 AD, Emperor Zhang of Han died, and ten-year-old Liu Zhao became Emperor He of Han, with Empress Dowager Dou holding court regency. Because Cai Lun had rendered meritorious service to Empress Dowager Dou, he was soon promoted to Chief Eunuch, specifically managing Emperor He's daily needs and also participating in court affairs decisions.
In 97 AD, Empress Dowager Dou passed away, and Emperor He began to take control of the government. In 102 AD, Emperor He established Deng Sui as empress, and Cai Lun quickly became Empress Deng's trusted confidant. Empress Deng enjoyed writing and painting, so Cai Lun submitted a memorial to the emperor, requesting to serve as the Director of the Imperial Workshops, a request the emperor granted. The Director of the Imperial Workshops was an official in charge of the palace's handicraft workshops and utensils, and all the tools Empress Deng used for calligraphy and painting had to undergo Cai Lun's meticulous inspection.
Once, Cai Lun went to inspect a folk handicraft workshop and saw a woman by the river spreading silk floss on a thin bamboo mat, then dipping the mat into the water and shaking it back and forth to wash it. After washing, a thin layer of silk floss residue usually remained on the mat. Cai Lun peeled off this residue while it was half-dry and half-wet, and found that he could write on it. This suddenly sparked an idea in his mind: if he soaked waste materials like tree bark, cloth scraps, and wheat stalks in water to fully saturate them, then pounded them into a pulp with a wooden mallet, and processed them through a series of steps, could he produce paper? Thinking this, Cai Lun hurried back to the palace and immediately ordered the palace workshop to collect raw materials. After boiling, pounding, and many experiments, they finally made paper. Cai Lun then presented the paper, along with the production process, to Emperor He of Han, who was very pleased and ordered its widespread production across the country. Because the raw materials were simple and easy to find, and the production process was not complicated, this paper quickly gained popularity among the people. To commemorate Cai Lun's papermaking technique, people named the paper he created "Cai Hou Paper."
In fact, as early as the Western Han Dynasty, China had already begun producing paper; during the Wei, Jin, and Southern and Northern Dynasties, the use of paper spread across the entire country, papermaking technology became much more advanced than before, the raw materials for paper became diverse, and the names of paper types were dazzling, including bamboo screen paper, rattan paper, and fish-egg paper.
The paper invented by the Chinese was not only popular within the country but also highly sought after in other Asian nations, where people tried every means to uncover the secrets of Chinese papermaking, though the imperial court kept it strictly confidential. It was not until the Tang Dynasty that the Arabs captured a group of Chinese papermaking workers, allowing the technique to spread abroad; soon, all Arab countries were using paper made with Chinese papermaking methods. Subsequently, the Arabs brought papermaking to Europe, where it replaced European parchment and vellum; in Greece, Rome, and Egypt, the spread of papermaking gradually replaced local papyrus.
With Cai Lun's invention of papermaking, daily life for ancient people became much more convenient. Before paper was invented, people wrote on bamboo slips, often finishing an entire roll of bamboo slips without completing a single article, and transporting these bamboo slips was also very troublesome. Early paper freed people from heavy bamboo slips, but the technology at that time was not advanced, and the paper produced often suffered from ink bleeding and tearing. It was not until Cai Lun invented plant fiber paper that writing truly became convenient. Cai Lun's papermaking, along with the compass, movable type printing, and gunpowder, are known as the Four Great Inventions of ancient China. They are treasures that the Chinese nation takes pride in and have made significant contributions to the development and spread of world culture.
After Emperor He of Han died, his infant son, only a few months old, ascended the throne but unfortunately died shortly after. Empress Dowager Deng then brought in Emperor He's nephew, Liu Hu, the son of Liu Qing, Prince of Qinghe, to be emperor—this was Emperor An of Han. Court affairs were temporarily controlled by Empress Dowager Deng, and Cai Lun was enfeoffed as the Marquis of Longting. In 119 AD, Cai Lun was promoted to Grand Tutor of Changle, and all civil and military officials held him in great awe. However, this good fortune did not last long. In 121 AD, Empress Dowager Deng passed away, and Emperor An of Han took power. Because Cai Lun had once conspired with Empress Dowager Dou to frame Emperor An's grandmother, Consort Song, and had also demoted Emperor An's father from crown prince to Prince of Qinghe, Cai Lun knew Emperor An would not let him off, so he chose to commit suicide to atone for his crimes.