Introduction

Hemp, a member of the Cannabaceae family, is a versatile and eco-friendly plant that has been used for centuries. Known as industrial hemp, this non-intoxicating variety of Cannabis sativa L. is grown for its flowers, seeds, and especially its fibers. With increasing emphasis on sustainability, hemp is being reconsidered as a viable alternative to cotton and synthetic fibers. This article explores the fascinating journey of hemp from cultivation to the creation of durable and comfortable fabrics.

Types of Hemp Fiber

The stalk of the hemp plant produces two types of fibers: long (bast) fibers and short (core/hurd) fibers. Bast fibers can be cleaned, spun, and then woven or knitted into many fabrics suitable for durable and comfortable clothing and housewares. Hurd fibers, on the other hand, are often used as a substitute for wood in the production of paper, insulation, and animal bedding, as well as composites for building materials.

Step 1: Cultivation

Planning and Sowing

The journey of hemp fabric begins with meticulous planning. After selecting the appropriate hemp variety and preparing the soil, the seeds are sown. The goal during sowing is to achieve a homogeneous and rapid emergence of the crop. Hemp, known for its resilience, generally requires minimal crop protection measures.

Growth and Maintenance

Once the seeds are sown, hemp grows rapidly, typically reaching maturity within 80-100 days. During this period, the plant does not require significant intervention. Its robust nature makes it resistant to many pests and diseases, reducing the need for chemical pesticides.

Step 2: Harvesting for Textile Fibers

Harvesting time is crucial for the quality of the fiber. Hemp is a fast-growing crop that can be harvested 80-100 days after sowing. To obtain a good fine fiber quality, both for technical and textile applications, harvesting in the Netherlands takes place around the time of flowering, from late July to early August. At this stage, the bast fibers have reached the ideal balance of strength and fineness. Special harvesters cut the hemp stalks into two pieces, each about one meter long. These pieces are then arranged in parallel rows, called windrows, in the field. This arrangement allows the stalks to be processed on a flax scutching line after retting.

Step 3: Field Retting

After harvesting, the hemp straw remains on the land for several weeks for retting, a natural process where the harvested hemp stalks are left on the field to break down the bonds between the bast fibers and the woody core. This decomposition is facilitated by microorganisms and weather conditions, primarily rain and dew, and can take anywhere from two to six weeks. To ensure uniform retting, the stalks are turned several times during this period. Proper retting is essential to avoid over-retting or under-retting, both of which can compromise fiber quality.

Step 4: Baling and Drying (Storage)

After retting, the hemp straw is dried to a moisture content below 18% and then pressed into bales. These bales are stored in a dry environment until they are ready for further processing.

Step 5: Scutching

Scutching plays a vital role in processing hemp fibers by using machines to beat the stalks, separating long fibers from the shives and further refining them for textile production. In smaller or traditional settings, manual scutching involves workers using knives or wooden tools to hand-scrape fibers, meticulously separating bast from core. Following scutching, long fibers undergo hackling to create fine yarns, while after additional cleaning, short fibers can be utilized for coarser yarns or cottonized to resemble cotton fibers. Shives find application in various uses such as building materials or animal bedding, completing the versatile processing cycle of hemp.

Step 6: Processing Long Fibers, Short Fibers, and Cottonized Hemp Fibers

Long Fibers (Line Fibers)

Long fibers, also known as line fibers, are the premium quality fibers used for fine textiles. These fibers undergo additional processes like hackling, where they are combed to remove short fibers and impurities.

Short Fibres (Tow Fibres)

Short fibers, or tow fibers, are the byproducts of the scutching and hackling processes. These fibers are shorter and less uniform than long fibers but can still be used in various applications.

Cottonized Hemp Fibres

Cottonized hemp fibers are processed to resemble cotton fibers in length and texture, enabling them to be spun on conventional cotton spinning equipment. This process uses whole bast fibres and short fibres from the scutching and hackling processes.

Step 7: Hackling

After scutching, the next step is hackling, which is a type of combing. In this process, fibers are pulled through fine pins to remove any remaining woody particles and to separate the short fibers from the long ones. The long fibers are then spread out, layered, and twisted into a continuous sliver. The hackled sliver is turned into bales, ready for further processing.

Step 8: Spinning

Spinning Long Fibers

Long fibers are processed through wet spinning or semi-wet spinning. Wet spinning produces fine, smooth, shiny yarns used for clothing and home textiles, while semi-wet spinning results in slightly coarser yarns.

 

Spinning Short Fibers

Short fibers from the scutching line undergo dry spinning, while hackling tow fibers are processed through semi-wet spinning.

Spinning of Cottonized Hemp Fibers

Cottonized staple fibers can be spun using either ring spinning or rotor spinning machines. Ring spinning is ideal for high-quality yarns, while rotor spinning is faster and produces yarns suitable for coarser textiles.

Twisting and Winding

Finally, the fibers are twisted into yarn by a rotating guide, adding strength to the yarn. Wet spinning produces fine, smooth, and shiny yarns ideal for high-quality textiles.

After spinning, hemp fabric is produced through preparatory activities like warping and sizing, followed by weaving or knitting, and finally undergoing finishing treatments to enhance its properties and appearance.

Conclusion

The journey from hemp cultivation to fabric production is a testament to the plant's versatility and sustainability. By rediscovering and refining these traditional methods, hemp is positioned as a strong contender in the textile industry, offering an eco-friendly alternative to conventional fibers. From cultivation to the final yarn, each step in the process contributes to creating high-quality, durable, and sustainable hemp fabrics.

Embracing hemp not only supports sustainable agriculture but also contributes to reducing our carbon footprint. The resurgence of hemp in the textile industry marks a return to natural, eco-friendly practices that benefit both the environment and consumers. Through these detailed steps, we see how hemp transforms from a simple plant into a sophisticated and sustainable textile, ready to meet the demands of modern, eco-conscious consumers.

Resources:

1. https://textileengineering.net/types-properties-and-uses-of-hemp-fibre/#google_vignette
2. https://www.sciencedirect.com/science/article/abs/pii/B9780128245286000138?via%3Dihub