How is Hemp Made Into Clothes?

A step-by-step guide from farm to factory

Industrial hemp is a hardy plant that requires a fair bit of work to turn into fabric for our clothes. Compared to cotton, the process is more time consuming and labour-intensive, contributing to why hemp clothes are so expensive.

When grown for fibre, hemp seeds are sown close together to encourage upwards growth, as hemp’s fibres run up and down the plant’s tall stalk.

These types of fibres – known as bast fibres – are strong and durable, partly due to their length. A natural gum binds these fibres together to enhance the stalk’s strength .

As well as the bast fibre and gum, hemp stalks also include a woody core known as the hurd. After harvesting, these components need to be separated.

Retting the hemp

‘Retting’ is a process intended to partially break down the gum, loosening the fibre and hurd.

After harvest, hemp stalks are typically left in the field for around six weeks. During this time, the plant’s cellular structure begins to denature. Known as dew retting, this is a traditional method that requires low resources, but affects the plants unevenly due to uncontrollable natural elements.

Water retting is a fast and common alternative to dew retting, although resource-heavy. The science is the same, but to speed up the process the hemp is submerged in water for around two weeks. Not only is this more efficient, but also more controllable.

Enzymatic, or chemical retting, is a contemporary approach that employs special enzymes to rapidly break down the pectin in hemp, in as little as 48 hours.

These are just some of the common approaches to retting. Once ret, the hemp needs to dry out out before the next actions can be performed.

Breaking the hemp

Once the bond between fibre and hurd has been weakened, they can be separated. This is done by physically breaking the hemp stalks, and was once (and is still sometimes) done by hand.

We now have decorticators to assist with this. These industrial machines employ rollers, grinders and blades to separate hemp hurd and fibre.

Some decorticators allow the hemp to be processed immediately after harvest, without retting, however retting is recommended for higher quality textile fibres.

Decorticators have empowered hemp farmers with the necessary efficiency to compete in the modern textile industry.

Purifying and isolating the fibres

Now that the fibres are separate, finer processing is needed to remove the very last of the flecks of hurd and unwanted organic matter.

Known as scutching, this can be done by hand or with specialised machinery.

The result is refined fibres called ‘tow’, and flecks of hurd called ‘shives’.

Combing the fibres

To prepare the fibres for spinning, they need to be straightened and brought into alignment with one another.

The hemp fibres are physically combed (or brushed), either on a small scale with hand tools or on a large, industrial scale with machinery.

The result is a mass of fibres, ready to be spun into yarn…. almost!

Hemp cottonisation is a modern and relatively new innovation that makes hemp as soft and wearable as cotton.

This step is what creates the distinguishable difference between contemporary hemp clothing and ancient hemp clothing that was, historically, coarse and a little scratchy.

Because existing spinning technologies have been designed for our most dominant crop, cotton, hemp needs to be modified to act like cotton in order to be compatible and processable. Cottonisation can involve a number of processes, but primarily aims to remove hemp’s natural gum, soften the fibres and shorten their length to mimic cotton’s short, staple fibres.

There is no one strict way to do this – it can be mechanical, enzymatic and/or chemical. Each method requires varying resources, and generates varying results and outputs.

A final note

The environmental impact of how hemp is processed is often not disclosed by fashion brands, who are keen to make sustainability claims.

Is it still sustainable by the time we wear it?

Industrial hemp is proven to sequester more CO² than any other commercially available crop, however some reports suggest that the CO² generated from processing hemp can sometimes far exceed what the crop sequesters, and also exceed that of cotton’s value chain.

This is something I’ll explore in another article.

It’s important not to assume that all hemp is equal and inherently low-impact. As consumers, we must demand transparency from fashion brands and question all sustainability claims.

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