Chapter 7 Section 2 Degumming Technology of Hemp Fiber

The bast on the surface of the stems of hemp plants is composed of cellulose, lignin, pectin and other impurities. If you want to make better use of hemp plants for textiles, you must not only obtain its bast layer, but also remove the bast layer. Gum and impurities, the spinnable fibers in it are separated and extracted.This process of separating and extracting hemp fibers is called "degumming" in modern textile technology. The method of using the phloem of the hemp plant in ancient China can be roughly divided into three stages according to the course of its process.The earliest method is to directly strip without degumming.That is to peel off the epidermis of the hemp plant branches and stems by hand or stone tools, uncover the bast fibers, roughly arrange them, and use them directly without degumming.This method was widely used in the Neolithic period. Some rope ends unearthed in Hemudu were observed under a microscope, and it was found that the hemp fibers used were all flakes without degumming traces, indicating that they were made in this way.

Followed by the retting method.With the accumulation of human life practice and production labor practice, people got enlightenment from the natural decay of hemp plants lodging in low-lying and humid places, and understood that the gum part of hemp plants can be detached by retting, and began to consciously adopt artificial retting The method of soaking to extract its fibers.The linen sheets unearthed from the Qianshanyang Neolithic site in Zhejiang Province and some Shang and Zhou tombs have obvious degumming traces after identification. The records about the retting and degumming method were first seen in "The Book of Songs·Chen Feng": "The pool of the East Gate can be retting", "The pool of the East Gate can be retting".This is an approach that has some scientific justification.Under sunlight, the pool water with slow flow rate has a higher temperature, and the number of microorganisms in the water can increase rapidly.In the process of growth and reproduction, they need to absorb a large amount of colloids of hemp plants soaked in water as their own nutrients, which objectively plays a role in degumming.Therefore, the number of microorganisms in water becomes the key to retting.

The reproduction of microorganisms is related to the retting season, retting water quality and retting time. Our ancestors have also made many scientific conclusions about this. Regarding the retting season, the "Book of Fan Fan" written in the Western Han Dynasty clearly pointed out: "It is best to be 20 days after the summer solstice." This is a very commendable conclusion, because the temperature is relatively high at this time , the bacteria multiply quickly, the degumming is smooth, and the hemp fiber that is very soft and similar to silk can be processed. Regarding water quality and retting time, Jia Sixie [xie Xie] of the Northern Wei Dynasty also clearly pointed out in "Qi Min Yao Shu": "Retting is for clear water, but turbid water will be black. If there is less water, it will be numb and brittle. Raw and ripe are suitable, but raw Difficult to peel, if it is too rotten, it will not be allowed." It means that the water quality should be clear, and the hemp retting in turbid water will turn black and have poor luster; , the produced fiber is brittle and easy to break, the retting time should be moderate, too short, the microbial reproduction is not enough, and enough colloid cannot be removed, and the hemp fiber is not easy to separate; too long, the microbial reproduction is large, and too much colloid is removed , fiber length and strength are easily damaged.

Then the boiling method and the ash treatment method were adopted. The boiling method is to boil the newly cut hemp plant (with skin) or the peeled bast in water to make it degummed. When the glue is gradually removed, take it out and lightly beat it with a wooden stick. , the dispersed fibers can be obtained.The method was probably first used on kudzu fiber, because the single fiber of kudzu is relatively short, most of which are less than 10 mm. If it is completely degummed, the single fiber will lose its textile value in a dispersed state, so the only method is semi-degummed.Using the method of boiling, the effect is relatively uniform, and it is easy to control the time and water temperature.The earliest record is also found in, "It is mow [yi meaning] is 翩 [huo harvest], for 絺 for 绤" describes the processing process of kudzu, to the effect that after kudzu is cut, it can be boiled in water. After boiling, it can be further spun into Gebu of different thicknesses.Since the Qin and Han Dynasties, this boiling method has been widely used in the degumming of ramie, and its technical level is getting higher and higher.

The ash treatment method is roughly the same as the scouring process in the modern hemp refining process. It is to twist the semi-degummed hemp fiber into hemp yarn, and then soak or boil it in an alkali solution to make the residual colloid on it as much as possible. Continue to fall off, making the hemp fiber softer, and can weave high-grade hemp fabrics.Its origin can also be traced back to before the Qin Dynasty.The earliest narrative can be found in "Miscellaneous Notes" and "Mourning Clothes" of "Yi Li".The "Nongsang Collection" compiled in the early Yuan Dynasty contains a method of processing hemp fiber, which is basically the interpretation of this method. "After the weaving is completed, wrap it into a tassel, soak it in a water jar for one night, and when the spinning wheel is spun [Qi Qi], use mulberry firewood ash, soak it in water for one night, and take it out. For every five liang wrapped, you can use a cup of clean water. Mix fine lime, put it in a container, park it for one night, choose to remove the lime, but when it is boiled with millet straw ash, it will become white and soft naturally, and it will be dried in the sun." Mulberry wood ash and millet straw ash are the so-called ashes of ash. The aqueous solutions of these ash are all alkaline and have a good degumming effect, which is used for ash treatment.In addition, in the "Nongshu" written by Wang Zhen of the Yuan Dynasty, there is also a similar method that combines sun exposure: "First, the hemp skin is made into long strands and spun into yarn, mixed with quicklime for three to five days, and placed on the Lime water is boiled, and then rinsed with clean water, spread on the bamboo screen spread on the water surface, half-dried and half-soaked, sun-dried and night-harvested, until the linen yarn is white." This is undoubtedly the result of the former ash treatment. developed on the basis of.Half-soaked and half-dried is beneficial to the interface chemical reaction of ultraviolet rays to generate ozone, oxidize the impurities and pigments in the fiber, and turn the pigment group into a colorless group, so that it can be bleached while refining, and more It is conducive to weaving high-grade linen fabrics.In some Han Dynasty linen cloth unearthed in recent years, such as the fine ramie cloth unearthed from the Mawangdui Han Tomb in Changsha, most of the fibers are in a single and separated state, and only a small part of the colloid remains on the hemp fiber.The flax unearthed from the Western Han Tomb in Fenghuang Mountain, Jiangling, Hubei, has more calcium ions attached to the fiber surface.According to this analysis, the degumming methods used for these unearthed cultural relics are most likely the above two ash treatment methods.Because these two ash treatment methods are very effective, they have been popular all over the world since their appearance, and are still used in the production of linen today.