Since bamboo slips and silks, literature has suffered from moths, and since the appearance of paper books, the problem has become more serious. Therefore, in the process of making literature carrier, the ancients should not only pay attention to the durability of the carrier, but also take various methods to avoid the damage of literature by insects.

Today, let's learn about a kind of smoke-free paper that first appeared in China.

This is a kind of paper made of Phellodendron amurense juice, also called "Huang Zhi". Phellodendron amurense, also known as Phellodendron amurense, is mainly produced in Sichuan and belongs to deciduous trees of Rutaceae. Its bark contains juniper, a small amount of alkaloids and some crystal substances without nitrogen, which is classified as heat-clearing and purging powder by Chinese medicine. In ancient China, phellodendron amurense juice was widely used as a yellow dye and a good insecticide.

As early as the Han dynasty, people knew to dye paper with phellodendron bark. In the 2nd century, the word "yellow" was explained, which means to dye paper. It can be seen that people clearly dyed paper with phellodendron amurense juice before this. Wei Boyang, an alchemist in the Eastern Han Dynasty, also wrote in the Book of Changes: "If you dye it yellow, it will turn green." Ge Hong of the Eastern Jin Dynasty also mentioned dyeing paper with cortex phellodendri juice in Bao Puzi, and personally experimented successfully with this juice to impregnate hemp paper, which soon spread. Lu Yun's Collection of Lu Shilong in the Western Jin Dynasty, Volume 8, A Letter with Brothers in the Plain, Lu Yun said to his brother, "There are 12 volumes of elder brother's essays in the previous collection, and eleven volumes are appropriate." The paper used for writing articles should be dyed yellow to prevent insects from eating. Xun Yu, a contemporary of Lu, also said in Preface to Mu Tianzi: "I would like to write it on two feet of yellow paper." The "yellow paper" here also refers to the paper dyed yellow. According to Mi Fei's History of Song Dynasty, Wang Xizhi and his writing paper are basically yellow hemp paper.

During the Wei, Jin, Southern and Northern Dynasties, there was a huge amount of religious paper, especially when copying Buddhist scriptures and Taoist scriptures, yellow paper was often used. In Dunhuang, Stein wrote the classic "The Book of Saint Man Jing" in yellow paper in the fourth year of Northern Wei Yanchang (5 15). In fact, a large number of Buddhist scriptures unearthed in Dunhuang Grottoes were written by the Tang Dynasty and well preserved. One of the reasons is that most of them are written in yellow paper.

At that time, people had a complete understanding of yellow dyed paper. So, what was the practice of ancient paper dyeing? The Book of Qi Yao Min in the Northern Wei Dynasty has a very scientific description of this: "If you want to make paper, you must have a strong life, so it is especially suitable to enter the Yellow River. The yellow paper is white, not too deep, if it is deep, it will turn black with age. Berberis is soaked, so it's useless to abandon me. Just use pure juice. When the Berberis are cooked, cook them with the method of pounding me, press them into a cloth bag, and then cook them. Boil it three times, and if you add pure juice, you will save four times, which is clear and clean. Write a book, and then go to the yellow after the summer, and the seam will not burst. Its new writer must iron it with an iron, or it will fall apart if it is not ironed. "

During the Sui and Tang Dynasties, the yellow dyeing technology was more widely used and more mature. According to the Six Classics of the Tang Dynasty, in the 13th year of Zhenguan (649), Li Shiming of Emperor Taizong set up a "nine-cooked paper ornament" in Hong Wen Pavilion. The secretary has appointed "ten paper cooks and ten painters". It is also stipulated that some official documents and religious classics should use yellow paper. "Four Books" said: "Zhenguan, written in yellow paper. In the second year of Gao, he said:' The imperial edict will be carried out forever, written in white paper, and there are many insects. It is advisable to order Shangshu Province to grant the state in the future and use yellow paper. ""It can be seen that dyeing paper into the Yellow River in the Tang Dynasty has already spread all over the country, and the government has also formulated relevant systems. It can be seen that both the people and the government attached great importance to book protection at that time.

The method of dyeing yellow was also described in Eight Records of Zunsheng in Ming Dynasty: "One catty of phellodendron amurense was mashed, soaked in four jins of water, and punished to two liters. Listen to a liter of oak barrel and fry it in water. Listen to rouge for five yuan, the deeper the better, and extract red with four bowls of soup. Each of the three flavors turns into thick juice, and the juice is packed in a big basin. Guanyin curtain should be dragged once with cork juice, once with oak barrel juice and once with rouge juice every time it is made into thick paper. Look at the depth of addition and subtraction, one by one. " It can be seen that the Ming people not only inherited the method of dyeing yellow, but also boldly innovated, adding acorn horn water and rouge water, which made the book protection take another big step.