Hemp had a bad reputation due to being classified incorrectly as an illegal drug. That’s why it was kept under wraps among established fashion brands for quite some time. Today, however, with more than 70 varieties, we see it as a critical fibre in our sustainable fibre toolkits. While many fashion and apparel brands use hemp for its durability due to its long staple lengths, denim requires a “cottonization” process to shorten, refine, and clean the hemp before weaving it into denim textiles.
MECHANICAL Vs. CHEMICAL COTTONIZING OF HEMP
The cottonization process removes ‘lignin’ (organic polymers that form crucial structural materials in the support tissues of plants) that hold the hemp fibres together. Lignin is what gives stalks their rigidity and acts like glue that holds the plant cell wall together.
During the Chemical Cottonization Process, hemp fibre is treated with chemicals for delignification, AKA removing the lignin. The key point of this process is to remove all “binding” and “filling” materials around the fibres from the stems (lignins, hemicellulose, gums and pectins) while leaving only pure cellulose in its natural form of thin cellulosic fibres. As you can imagine, the amount of water used and the nature of the chemicals involved can impact the sustainability of the fibre.
On the other hand, the mechanical process uses a series of machines to break down the hemp stalks into a finer fibre.
COTTONIZING HEMP STEP BY STEP WITH MARMARA HEMP
A few weeks ago, I had the absolute honour of visiting Marmara Hemp, the first Cradle to Cradle Platinum supplier for mechanically cottonized hemp.
Marmara Hemp was born out of a partnership between three leading hemp producers in France, an experienced manufacturer, and a distributor guaranteeing consistent quality and quantities with added traceability.
The process starts from non-GMO seeds on farms that use no fertilizers, phytosanitary products, or irrigation 👏 Based on experience, farmers can see if their soil is happy or not. If the farmer feels the pH levels need to be adjusted, they can do so by adding manure, for example.
Additionally, testing the pH levels of the soil is important for measuring soil health improvements over time. Hemp’s roots are short but thick, which opens the soil and lets it breathe, increasing soil health for the next crop. Speaking to Marmara Hemp and their analyses, a pH level of >6 is ideal for optimal soil health!
Roots of hemp plant
After the growing season, the hemp straw is cut and left in the field for the retting process, where the bast fibres begin to separate from the stalks (woody core) through a microbial process that breaks the chemical bonds that hold the stem together.
Now we enter the processing facility for ‘decorticating’! Decorticating is where the woody interior is mechanically separated from the bast fibre by going through a big tumbler-like machine. It goes through this machine twice to ensure the woody core has been successfully removed from the bast fibre.
What the bales look like before decorticating
What happens during decorticating
An overview of the entire decorticating process
These tubes act like vacuums that carry the material to and from machines
After the decorticating process, the bales of hemp are selected for their purpose (textiles, agriculture, construction, etc.) and blended to achieve uniformity.
Finally, we reach the cottonization stage! In this stage, we are bringing the hemp staple length down about 15 - 20 cm to achieve an average cotton staple length of 35 mm, while also cleaning the fibre in just 25 minutes. In the video below, you will see the fibre being cottonized, moving through rotaries with teeth that move 1300 turns per minute 😱 No wonder these fibres are processed in only 25 minutes!
For a summary of the entire process from seed to cottonized fibre, check out Marmara Hemp’s video here.
We are lucky to have the opportunity to touch many different industries through fashion. The fact that our raw materials are miraculously nurtured from seed to living organisms blows my mind. What’s more, we have the opportunity to care for these life forms, and when we do, they will care for mother earth.
For those unfamiliar with the different approaches to processing hemp, ask your suppliers where it is coming from and about their processing techniques. Always be curious and stay diligent!
Until next time, friends :)