His position in the Palace Workshop increased in scope; he became responsible for the production of ceremonial weapons, which the Hou Hanshu reports were of exemplary craftsmanship.

However, Cai's most noted innovation was in 105 CE, when he substantially improved the papermaking process with the use of tree bark, hemp waste, old rags, and fishnets.

Cai was rewarded for his imperial service in 114 CE; he received the title of marquis, and was enfeoffed lord of Longting [zh], a small village.

When his ally Deng died in 121 CE, Cai was ordered to the Ministry of Justice because of his involvement in the death of the emperor's grandmother, Consort Song.

Ashamed at his predicament and expecting to be sentenced to death, he committed suicide that year and died in the capital city in which he had spent almost his entire adult life.

Cai's improvements to paper-making are considered to have had an enormous impact on human history, and of those who created China's Four Great Inventions—the compass, gunpowder, papermaking and printing—Cai is the only inventor whose name is known.

The main source of information on Cai Lun is just 300 characters in volume 78 of the Hou Hanshu (後漢書; Book of the Later Han), an official history compiled by the Liu Song dynasty historian and politician Fan Ye.

[6] The primary source Fan used was the 2nd-century Dongguan Hanji (東觀漢記; History of the Eastern Han),[7] in which Yan Du [zh] is credited as the author of Cai's biography.

[9][b] Later history books, such as the Song dynasty's Shiwu Jiyuan [zh] (事物紀原; Compound Source of Matters and Facts), also include Cai and his work in papermaking.

[10] However, some major history books, such as the Annals of the Later Han and Zizhi Tongjian (Comprehensive Mirror in Aid of Governance) do not mention Cai's papermaking achievements.

[10][c] Sinologist T. H. Barrett suggested this was because "Cai Lun was, after all, a palace eunuch, precisely the sort of person normally viewed with antagonism by the regular bureaucrats who controlled the writing of official (and even most unofficial) history.

"[10] Cai Lun was born in Guiyang Commandery (桂阳郡; modern-day Leiyang, Hunan province)[5][‡ 2] in the Eastern Han dynasty (25–220 CE).

[22] Narita cited Cai's future court appointment to oversee the production of weapons, especially swords, as evidence that he must have learned the skills to do so earlier in his life, likely from the iron foundry.

[29] However, Ma's death in 79 CE made Lady Dou the empress, and—aiming to develop her family's power—she adopted Prince Zhao with the intention of installing him as heir.

[45] After Meng Tian purportedly created an animal-hair brush for writing in 3rd-century BCE, silk and cloth became alternatives that addressed these issues, but they were too expensive for widespread use.

[48] This event and its context are relayed in an often cited passage of the Hou Hanshu:[g] 自古書契多編以竹簡，其用縑帛者謂之為紙。縑貴而簡重，並不便於人。倫乃造意，用樹膚、麻頭及敝布、魚網以為紙。元興元年奏上之，帝善其能，自是莫不從用焉，故天下咸称蔡侯紙。 In ancient times writings and inscriptions were generally made on tablets of bamboo or on pieces of silk called chih.

[4][‡ 10] In 114 CE, he was awarded the title of marquis and the imperial court enfeoffed him as the lord of Longting [zh], a small village of 300 families[54] in modern-day Yang County, Shaanxi.

[4][‡ 12] Due to modern archeological investigations, it is now certain that different forms of paper existed in China as early as 3rd-century BCE,[56][h] though the findings do not necessarily discount the credit given to Cai.

[57] The Chinese scholar Tsien Tsuen-hsuin explained that the term used in Cai's ancient biography, zào yì (造意), can be understood as "to initiate the idea", meaning that he furthered the ongoing process with the addition of important materials.

[63] Cai's improvements to paper and the papermaking process are considered especially impactful to human history,[65] as they resulted in the spread of literature and knowledge around the world, and advancements in communications.

[67] The scholar of paper history, Thomas Francis Carter, drew parallels between Cai and Johannes Gutenberg, the inventor of the first printing press which was movable type, calling them "spiritual father and son" respectively.

[23] In this version, Hui convinced Cai Mo to learn the new papermaking trade from his younger brother, and when he returned in only three months, the paper he and his wife produced was too low quality to sell.

[79] Then, their neighbors checked in on them, and Hui sprung out of the coffin, explaining that the burned money was transferred to her in the afterlife, with which she paid ghosts to return her from the dead.

[84] In 1267, a man named Chen Tsunghsi raised funds to repair the long-damaged shrine, and renovated it to include a statue of Cai and a mausoleum.

[90] The conflict began when the shenfubang of Yingjiang claimed that their statue of Cai—which they carried throughout Jiajiang County annually—gave them ritual supremacy over Macun and Zhongxing papermakers, whom they demanded pay for and take part in their celebrations.

[90] The shenfubangs from Macun and Zhongxing denied the demand, citing their long history of worshipping Cai, which resulted in increasing conflict between the sides and eventually a lawsuit.