In ancient documents, we can often see records of writing books on "yellow paper". "The Biography of Emperor Mu" by Xunxu of Jin Dynasty said: "I would like to write it on two feet of yellow paper"; "Book of Jin·Biography of Liu Bian" records that when Liu Bian entered the Imperial Academy, "the official visit order was written on yellow paper and a deer cart". The "Explanation of Customs" in Song Qi's "Song Jingwen Gong's Notes" in the Northern Song Dynasty said: "The ancients used yellow paper to write books, so they are called 'yellow scrolls'." This kind of "yellow paper" is dyed with barberry (cypress) juice. The color will turn yellow to prevent insect damage. This method of dyeing paper is called "ruhuang (also written as 'ruhuang')" or "dyeing yellow" in papermaking technology. Most of the paper scrolls were "yellowed", some were written on first and then dyed, and some were dyed first and then written on. Our country has long used drugs to protect books and paper. In the "Essential Art of Qi Min" written by Jia Sixie of the later Wei Dynasty, there is a section on "Dyeing Huang and Treating Calligraphy", which describes in detail the method of dyeing books with cork bark juice. Judging from the existing ancient manuscripts, many of them are damaged and broken, but there is little evidence of moth corrosion. This shows that this method of preventing moth is effective. If the paper scroll has wrong words, it cannot be scraped and corrected like a slip. The ancients either used paper stickers or painted them with powder, but the effect was not satisfactory, so someone invented the use of orpiment for correction. Orpiment, also known as cockscomb stone, can be used as a painting pigment to write on wrong words. Not only the color is similar to that of yellow paper, but the wrong words "are wiped out as soon as they are spread out, and they remain in place for a long time." This kind of correction method has been around in the Northern and Southern Dynasties at the latest. "Qi Min Yao Shu" has a section on "Dyeing Huang and Treating Calligraphy" after "Dyeing Huang and Treating Calligraphy"; Yan Zhidui of the Northern Qi Dynasty "Yan Family Instructions·Book Evidence" Chapter, there is also a record of "changing 'xiao' to '玎' with orpiment". Later generations ridiculed those who misinterpreted ancient books and made unreasonable comments as "bullshit." "Xinkou" means casually, but what is "orpiment"? It turns out that orpiment also has a scientific name: arsenic trisulfide, which is an orange-yellow, slightly transparent substance that emits a garlic-like odor when burned. People can use it as a pigment or fading agent. Selected Works·Liu Jun's "Guang Jue Di Dian Lun": "The orpiment comes from the kiss of the lips, and the vermilion comes from the moon." Li Shan's note quotes Sun Sheng of the Jin Dynasty from "Jin Yang Qiu": "Wang Yan, courtesy name Yifu, can speak well and has good intentions. Those who are uneasy will often change it. Orpiment is an orange-yellow mineral, which is not only used for painting, but also as a pigment. Among the more than 400 remaining words in the Sui Dynasty's "Selected Works: Theory of Destiny" that has been handed down to this day, there are 7 writings that have been covered with yellow paint, which are traces of orpiment.