What is hemp retting? In short, it’s the process by which the hemp plant can be made into commercial and industrial products. Here’s an overview of what it works.
The fibers from the stalk of a hemp plant are used to produce a plethora of products, including textiles, fabrics, rope and clothing. In order for the fiber to be useable, it must first be separated from the rest of the plant, including the cellular tissues and pectins that surround the fiber. This happens in a process called retting. Retting is a relatively challenging process, but there are various techniques that farmers can utilize.
Dew Hemp Retting
When farmers utilize the dew retting technique, they leave the hemp stalks outside and expose them to rain, dew or irrigation so that they stay constantly moist. Dew retting is often used in areas that have limited resources of water. The moisture causes bacteria to grow, which when combined with the sun and air produces fermentation. After what can take up to five weeks, the stem material around the fiber dissolves and a coarse fiber with a light brown color remains.
Water Hemp Retting
The water hemp retting technique calls for submerging bundles of hemp stems for seven to 10 days, which causes bacteria to break down the pectin. Water retting is the most commonly used retting process and it often produces a better quality fiber than dew retting. A relatively similar process, referred to as warm water retting, involves first soaking the stalks into water for 24 hours. The water is replaced and exposed it to heat for two to three days. Warm water retting produces a clean, uniform fiber.
Green Hemp Retting
The green retting technique is used when the fiber removed from the hemp stalk is going to be used to produce textiles, paper and fiberboard products. It’s a complete mechanical process that separates the fiber by hammering or using a hammermill or decorticator. While it doesn’t require any water or chemicals and can produce a large quantity of fiber in a short amount of time, it’s an expensive process and produces a lower quality fiber.
Chemical Hemp Retting
Chemical retting is the quickest of the various hemp retting processes. It involves boiling and applying chemicals, like sodium hydroxide, sodium benzoate and hydrogen peroxide, which dissolve the pectin and allow the components to separate. It takes just about 48 hours and produces a high-quality fiber.