How is hemp fiber made?
The steps involved in the manufacturing of hemp fibers are as follows:
• Cultivation and Harvesting:
Firstly, the seeds are sown and the soil employed for cultivation should be rich in nitrogen and non-acidic. The climatic conditions required for the optimal growth of the plant are mild and humid climate with rainfall of at least 25-30 inches. After seeding it takes about 70-90 days for the harvesting of hemp which is indicated as to when the plants begin to shed the pollen.
After harvesting, the next step is to remove the pectin substances that bind the fibers together in the hemp stalk. Thus, the stalks are kept in the water for about 4-6 weeks depending on the weather conditions. The mechanism behind the process of retting is to increase the moisture content of the stalk creating an environment for the growth of bacteria or fungi which eat up the pectin substances. There are two methods of retting i.e. ground and water retting.
- Ground Retting: As the name suggests, this method of retting involves laying the stalk on the ground and exposing them to the dew and rainfall which create an environment suitable for the growth of bacteria. However, the drawback of this method is that it is dependent on the rainfall and the process cannot be controlled.
- Water Retting: This method involves immersing the stalk in water tanks or containers. The stalks are lifted using the crane owing to its heavy weight and held under the water using wooden or iron frames. Also, higher temperature facilitates faster retting it a short time duration.
After enough exposure to bacterial growth under moist conditions, the stalks are arranged in the open field to let them dry. The stalks are then tied in bundles and sent for the next step.
• Fiber Separation:
- Breaking: This step includes the opening of stalk bundles and breaking the stalks along the length by passing the stalks through the rollers that crush them.
- Scutching: The hurds are then removed that might be left and the fiber bundles are softened and lignin is further removed.
The fibers thus obtained are utilised depending on the end product to be made such as matting to develop non-woven mats or steam explosion to obtain fibers for weaving.