After the fiber is harvested with flax, it is bundled into small bundles for retting and degumming. The temperature of hemp retting in warm water should be controlled between 28 and 32 ℃. After about 100 hours, it should be taken out, and the hemp stalk should be built into an umbrella and dried in the open. Rain and dew retting is to spread the harvested hemp stalks on the grass or flax ground, and then soak them in rain and dew, and then use mold fermentation to rett. Under the appropriate humidity conditions, after 7 to 10 days, the retted dry stems are broken, the xylem and impurities are removed, the fibers are combed, and then numbered according to the quality. The broken short hemp is called two coarse hemp.

The price of high-quality pure linen sold on the market is high. The price can also reflect the quality of linen. High-quality primary-color linen is brown, shiny and evenly absorbent. The flax is not good in quality. It is treated as a soft fiber flax, which absorbs water unevenly and will turn black after wetting. Check whether the thickness of the longitude and latitude lines is uniform through light transmission. If the warp and weft are too uniform, it may be cotton fabric.