Fabric series: All about Silk

What is silk?

The strongest natural protein fibre composed mainly of Fibroin, silk is a shimmering textile known for its satin texture and famous for being a luxurious fabric. 

The most common silk is produced from silkworms, small creatures which mostly live on mulberry leaves. The protecting cocoon created around themself is harvested and used for silk production. 

The global average of silk production accounts for 80,000 tons per year, of which approximately 70% is produced in China.

Where does silk come from?

Lei Zu was drinking in a wild mulberry bush when some wild cocoons fell in her bowl… 

The history of silk roots in China, where the production of the textile was kept as a secret for over 2,000 years. The origins of silk dates back to the Chinese neolithic era as the oldest silk example found has been dated to 3630 BC

Today, the main countries involved in the production of silk are China, India, Uzbekistan, Brazil, Japan, Thailand, Vietnam and Iran. Despite the small market share of silk in the Global Textile Market (around 0.2%), the production is spread around 60 countries all over the world.

China is the world’s biggest producer and main global supplier of silk, followed by India. 

How is silk made?

...When Lei Zu tried to fish out the cocoons, she found the silk thread unraveled in a never-ending line. She began to rear wild silkworms and spun to knit, Lei Zu is known as the “Goddess of Silkworms” in China.

The silk production process is called Sericulture. It begins with the cultivation of silkworms which, despite their name, aren't actually worms but larvae which would turn into moths. 

Fibroin is a protein fibre produced by larvae during their cocoon stage and consists of a continuous filament produced from the silkworms salivary glands. The silk production can be summarised into the following 6 steps.

1.  A female silk moth lays around 300-500 eggs per month. The eggs hatch into larvae which feed from the burberry leaves. During their growing process, the hatched larvae molt 4 times. 

2. When climbing onto a twig, they extrude some of the fibroin protein and create a net to hold themselves to the twig.

3. The netted larva swings itself while excreting the saliva that forms the silk. The silk solidifies and becomes a solid cocoon. In 2-3 days, the larva spins about 1 mile worth of silk filament around itself.

4. The next step is known as  the degumming process: The silkworm larvae is boiled to remove the sericin and free the filament. At this stage, the poor larva dies. 

5. The start of the filament becomes visible by gently brushing the boiled cocoon and is then wound onto a reel. One cocoon will produce around 1,000 yards of silk filament.

6. The single silk filaments are combined to form a strong silk thread which will be woven to produce fabrics. 

Varieties of Silk 

Mulberry silk is the bulk of silk produced around the world, especially in China, Japan and Korea. The name refers to the variety of silkworm which feeds entirely on mulberry bushes. They are domesticated and reared indoors which requires extra care to maintain its smooth texture. 

Another variety of silk is produced from various spider species including Nephila madagascariensis. Spider silk is the most difficult to produce as spiders do not produce as much silk and cannot be bred like silkworms. That makes this variety very expensive, reducing its common uses. It is one of the most durable types of silk and is used in the production of bulletproof vests and wear-resistant clothes.

Another commercially known type of silk is Tasar silk. It is produced from wild caterpillars, called Tasar silkworms. Due to its strong properties, this variety is mainly used in furnishing and it is mostly available in its natural color of copper since it is very tough to dye. 

Environmental Issues

It takes around 35,000 silkworm cocoons to make 5.5kg of raw silk. These 35,000 cocoons are produced from about 30g of silkworm eggs, which in turn require about a ton of Mulberry leaves to feed on.

Being a by-product of an animal, silk is not vegan. There are many criticisms about the production process of silk. For instance, PETA (People for the Ethical Treatment of Animals) campaigns against mass produced silk and appointed it to be the second-worst material for the environment, just after leather.  

Mahatma Gandhi was participating in criticizing the cruel process of producing silk as his belief was to “not hurt any living thing”.

Therefore, silk is considered highly unethical as the silkworms are boiled alive and killed during the extraction process. 

Which is the better textile?

The unethical production of silk has sparked many controversies and incited the use of  alternative textiles such as nylon, milkweed seed pod fibers, silk-cotton tree, polyester, and rayon. However, the conventional method of producing synthetic fibres is far from green due to the fact they derive from petrochemicals which are not renewable. They use energy-intensive technology, do not biodegrade and are not easy to recycle. 

Silk, on the other hand, is a biodegradable, compostable material. Compared to cotton, for example, there is far less impact on the land, water and air, and it doesn’t involve the use of pesticides.

In order to reach a compromise, there are entities working to improve the ways of producing silk either in the traditional or artificially ways, through laboratory methods.

Stella McCartney has new ways to create silk.

The English fashion designer is aware of the several environmental issues related to the fashion industry. As a modern brand, their investments on research and development aim to reduce their footprint under many points of view. 

Material innovations is one of their focal points. Stella McCartney decided to take action against the traditional production of silk and to find alternatives. In this purpose, they partner with technology innovator Bolt Threads. By studying the silk that spiders make and the way in which they make it, Bolt Threads were able to replicate these processes at scale, and create a vegan silk with remarkable properties. 

This partnership represents a huge step-change for the brand and for the future of fashion. 

What is Silk used in? 

The uses of silk are practically endless as it can be turned into different products. 

Silk fabric has withstood the test of time in the fashion industry. Clothes made from silk are considered to be high-end products due to the high quality of the textile and of course expensive prices. 

For sport clothing, silk fibre is blended with cotton to give more strength, stain resistance and sturdiness.

Silk is also used for home furnishings. Silk throws, pillows and curtains are examples of home decors.

The antibacterial property of the textile allows its use for medical purposes. Especially in the manufacturing of prosthetic arteries and for covering wounds and burns.

Moreover, woven silk fibres are often blended with other materials and are used for the construction of parachutes and bicycle tires.

What are the properties of the textile?

The texture is soft with a flattering sheen. It is one of the most absorbent fabrics and its flexibility makes it perfect for garments. Being a breathable material, air can pass through it and leads to feeling cooler.

Silk is a thin, but strong which makes the textile durable. However, it can be damaged when wet and exposed to too much sunlight. That means it is not easy to wash because the fabric shrinks easily. In order to avoid that, clothing items should be dry-cleaned. Read more about how to care of silk products here.

Between the benefits, silk is hypoallergenic as the sericin residue is a natural repellent that keeps away bacteria, dust mites and moulds. 

How can it be recycled?

As mentioned before, the fabric is pure, natural and biodegradable, better than synthetical alternatives from an environmental perspective and it has a much lower carbon footprint.

Silk is one of the natural textiles that is  compostable. Because clothes are often made from a blend of fabrics (often polyesters), it obviously impedes biodegradation. 

As all textiles, silk can be recycled by giving a new life to your clothes or any blends of fabric. You can check it on our blog post 10 things to do with your unwanted clothes.

Don’t ever stop to check what your clothes are made of. To find out more and learn about the most common fabrics, stay tuned on our blog for the next fabric series post. 

Sources:

https://inserco.org/en/statistics

https://modernarchive.de/blogs/news/japanese-kimono-silk-everything-you-need-to-know

https://www.chinahighlights.com/travelguide/culture/silk-facts.htm

http://www.silk-road.com/artl/silkhistory.shtml

https://khaleejmag.com/fashion/everything-you-need-to-know-about-silk/

https://www.stellamccartney.com/experience/de/sustainability/themes/materials-and-innovation/silk/

https://silkup.com/blog/what-is-silk-the-complete-guide/

https://amclub.co/blogs/news/10-fun-facts-about-silks-that-you-need-to-know

https://www.masterclass.com/articles/fabric-guide-what-is-silk-how-to-use-and-care-for-silk-fabric#8-primary-uses-for-silk-fabric

https://silkup.com/blog/what-is-silk-the-complete-guide/

https://www.masterclass.com/articles/fabric-guide-what-is-silk-how-to-use-and-care-for-silk-fabric#what-is-silk

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