Hemp is a variety of Cannabis. When employed for industrial use, one of the wonder products derived out of the hemp plant is hemp fabric. It is a biodegradable fabric made from the fibres in the herbaceous plant of the species Cannabis Sattiva.
Considering the history of hemp fabric, one must say that hemp was a hidden treasure not discovered by many. Hemp has a long history of being cultivated and used as a fabric. In fact, this fabric was highly famous in the 16th and 18th centuries. One can say that it is making its comeback here, after centuries.
The process of growing hemp is considerably much simpler than other similar plantations. The following steps are the traditional steps followed in growing hemp.
- The seeds are first sown densely for cultivation to produce desired rangy stems. These stems contain fine fibres.
- The plant is then harvested. The apt time for this is during the early to mid flowering stage.
- The plant fibres are then separated by laying them to break down in the weather. This process is known as ‘retting.’ Common techniques used to carry out this process include water retting and dew retting. Water retting involves soaking of the stem into water for approx. 1/3rd time of the month. Whereas, in Dew retting the crop is laid on the ground for approx. one to one and a half months.
- After retting, the stems or the stalks are broken through the mechanical process of separation which is called ‘breaking.’ This process is carried through fluted rollers or breakers. This device separates the woody core into short pieces.
- The remaining short pieces and fibre are separated in the process of ‘Scutching.’ The desired fibre is finally separated in this process.
- The fibres are then combed for the final removal of any remaining wood particles. This process is called ‘hackling.’
- The fibres are further aligned and set into bundles. This bundle is then twisted to improve strength through the process of ‘roving.’
- After this, the fibre is ready for spinning. The fibre is converted into yarns through the process of spinning. The hemp fibre can be spun using any of these 3 processes: cottonization, long fibre or tow processing. In cottonization, the hemp yarn is turned into a cotton-like texture. It removes the lignin that binds hemp fibre together in bundles. In tow processing, the short fibres are spun into a coarse yard using the wet or dry processes. In the wet process, fibres are made wet time and again in a small channel of water. Dry spun process is also used often; it might result in a coarser yarn.
- The long continuous yarn can be twisted together in different ways and then woven and knitted together to create a fabric. At this point, the fibres can be blended with others fibres like silk or cotton, if desired.
- After this, usually the fabric is washed and shrunk. The fabric obtained at this stage might be a bit heavy and stiff. This can be softened up either by chemical softening or using organic methods. Chemical softening can be done using caustic soda or other such acids. The organic method whereas uses biodegradable softening solutions for this purpose.
- At this stage, the fabric can be sent for dyeing. Once dyed, the fabric is treated against shrinkage. With this, the fabric is ready for creating a finished appearance.