What contribution did Cai Lun, a paper expert, make?

As an expert in papermaking, Cai Lun's contributions are as follows: First, he expanded the raw materials for papermaking. Besides hemp and ramie, we also make full use of other discarded hemp products-hemp heads, flax, fishing nets and so on. , especially bark. The source of bark is no less than marijuana. Paper based on bark is the most important paper. After the Eastern Han Dynasty, coated paper was one of the paper varieties produced and used in large quantities. Secondly, papermaking technology has been improved and developed. Old hemp products such as hemp rope ends, fishing nets and linen need to be mashed, and the darker ones need to be decolored. The content of lignin, pectin and other impurities in bark is much higher than that of hemp and ramie. Therefore, in degumming pulping, technical requirements are higher. According to analysis, it was possible to make pulp with grey water or mixed solution of grey water and lime water at that time. Because limewater contains calcium hydroxide, and limewater contains more potassium carbonate. Using grey water or mixed solution of grey water and lime water has moderate alkalinity, which can not only make pulp, but also not destroy cellulose. Cai Lun can use hemp rope, linen, fishing nets and bark to produce better quality paper. It must have made a great improvement in pulping technology, probably by using alkali liquor cooking first. Third, promote the use of paper and papermaking technology. Ancient technology is often kept secret, and it is only circulated secretly among a few craftsmen and apprentices, and papermaking technology should be no exception. In addition, at the beginning of the invention of papermaking, the quality of the paper made was very poor, and it was difficult to be exquisite. Until the mid-Eastern Han Dynasty, many scholars looked down on paper. In the compilation of Bei Tang Shu Chao, a story about Cui Yuan's gift of books was written. Cui Yuan was a scholar in the Eastern Han Dynasty. He wrote to his friend Ge (that is, Ge Gong, born in 1 from the end of the century to the beginning of the 2nd century) to the effect that he sent ten volumes of Xu Zi, and he had to write it on paper because of economic poverty, expressing great regret. This incident reflected the understanding of paper by some literati at that time. Cai Lun realized the importance of paper, so he summed up folk experience, improved and developed papermaking technology, made paper and papermaking a household name, and attracted the attention of the whole society. Cai Lun made high-quality paper, which made people realize that paper has the advantages of bamboo and wood, but it is light and thin, silky and soft, but it is not expensive, and it has a long history and is not as bulky as it is. Paper is the most ideal writing material, which is cheap and light. As a social demand, the paper industry has developed steadily with the development of social culture.