How Is Silk Made and Is It Sustainable?

Green silk textile

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Silk is one of the oldest and most valuable fabrics in the world. The smooth, durable fabric is made by harvesting the natural filament from the cocoons of silkworms, then dyeing, spinning, and weaving the threads. The use of silk in fabric was developed in ancient China; the first biomolecular evidence of silk dates back 8,500 years and was found at a Neolithic site in the Henan province.

Silk is a natural and biodegradable fiber, but its production has a larger environmental impact than other natural fabrics. For fabric with a comparatively lighter impact, look for certified organic silk. Alternatives include wild silk (made from the cocoons of wild moths after they have hatched) to synthetic spider silk (a new innovation in bioengineering).

How Silk Is Made

Sericulture, or silk-making, begins with cultivating silkworms (Bombyx mori). The white caterpillars feed on fresh mulberry leaves, and after molting four times as they grow, they spin a naturally secreted protein, which starts as a liquid, into a cocoon, which sticks together with a gum called sericin. The cocoon-spinning process takes 2-3 days.

If allowed to continue naturally, the silkworm then matures into a moth inside its cocoon. When the time comes, the now-moth secretes a fluid that burns a hole through the strands of its cocoon to emerge and fly off to complete its life cycle.

Silkworm cocoons in a silk factory
Silkworm cocoons in a silk factory. fototrav / Getty Images 

But in exiting the cocoon, the silk threads are damaged, so in silk production factories, the silkworms only live until they have cocooned themselves in their silken wrapping. Then, they are boiled, which kills the caterpillars and removes the sericin gum, and the silk filament is recovered intact.

The filament is unwound and combined with others to create silk thread, which is then collected on wheels, and then those threads are made into whatever thickness of yarn is needed to weave a piece of silk cloth.

It takes about 2,500 silkworms' worth of filament to produce about a pound of silk fabric.

Environmental Impact of Silk Production

Silk is a natural, biodegradable, and long-lasting fabric. However, overall, silk appears to have a larger environmental impact when compared to other natural fibers. According to the Sustainable Apparel Coalition's Higg Index, silk has a worse environmental impact than synthetic fabrics, too.

First, silk production takes a lot of energy. Silk farms have to be kept at controlled temperatures, and harvesting the cocoons uses both hot water and hot air.

Second, silk production uses a lot of water. The dependence on the mulberry, which is a thirsty tree, can stress freshwater supplies if the trees are planted in places where water is scarce, and large volumes of water are also necessary for several steps in the silk processing chain.

Third, the use of chemicals to clean and dye silk can pollute local water, hinder the fabric's biodegradability, and contribute to the toxic impact of the fabric.

If you're shopping for a silk product, try to buy secondhand, or look for silk that is certified organic by the Global Organic Textile Standard. GOTS establishes requirements for environmental management, water treatment, chemical inputs, and more throughout the textile supply chain.

The Silk Industry

Compared to other textiles, silk is a very small percentage of overall production, at just .2% of the global fiber market. But it's a high-value fabric, worth about 20 times what cotton is for the same volume, so that small percentage amounts to a market value of almost $17 billion in 2021.

In China, the largest silk-producing country in the world, the silk sector employs about a million workers. India, the second-largest silk producer, has a widely distributed rural workforce of 7.9 million. Sericulture can be a good way for small businesses and 'cottage' industries (small groups of people working together in their homes or nearby workshops) to keep production and income in rural areas.

The silk industry has been linked to child labor in India and Uzbekistan. In 2003, the Human Rights Watch estimated that 350,000 children in India work as bound laborers in the silk industry, many in "conditions of physical and verbal abuse." Additionally, workers in the silk industry face health risks and unsafe working conditions. According to a 2016 study published in the Journal of International Academic Research for Multidisciplinary:

Even though, the silk is based on natural origin, the silk industry involves certain health risks in all the segments of silk processing from mulberry cultivation to silk finishing includes pesticides and herbicides toxicity from mulberry field, carbon monoxide poisoning, unhygienic rearing, use of bed disinfectants causing breathing problems and acts as carcinogens.

Peace Silk and Wild Silk

Peace silk (also known as Ahimsa silk) is silk manufactured without killing silkworms. However, the Bombyx mori moth has been cultivated and bred by humans for thousands of years, and so they aren't able to survive long once they emerge from their cocoons. The moths can't see or fly, and as such, they aren't able to flee predators. They simply live a short life in captivity.

Wild silk (sometimes called Tussar or Tussah silk) is made from cocoons found in open forests where several species of wild moths live. The caterpillars eat a variety of plants and leaves, so the resulting fiber is less consistent than what cultivated silkworms produce. The cocoons can be harvested after the moth has hatched and flown away, or harvested with the larvae still inside. This silk has shorter fibers and a golden color; it is valued for its warm base tones.

Vegan Silk Alternatives

Because it is made from an animal product, silk is not vegan. As an alternative, silk-like threads can be made from several plant sources.

Stems of the lotus flower can be made into luxurious, silk-like fabric. Making a textile from lotus stems is an ancient practice, but it takes a huge volume of the stems to make a small length of the fabric. Another alternative is piña, a traditional Philippine fabric made from the leaves of pineapples. Piña has a silk-like texture and is lightweight, translucent, and stiff.

What About Spider Silk?

People have been trying to produce silk fabric from the strong, elastic webs of spiders for hundreds of years. Success, however, has been limited, since spiders tend to become cannibalistic when forced into close proximity for silk-making.

In 2012, the Victoria & Albert Museum exhibited the largest pieces of spider silk fabric ever made: a shawl and a cape produced with the silk of 1.2 million golden silk orb-weaver spiders.

A model wearing a yellow cape made from spider silk
Bianca Gavrilas models the cape made from the silk of the golden orb spider. Oli Scarff / Staff / Getty Images

A new and innovative alternative is synthetic spider silk. One textile company, Bolt Threads, used water, yeast, sugar, and bioengineered spider DNA to develop a material that is molecularly similar to spider silk. The fabric, called Microsilk, has the potential to be incredibly tough and durable. Bolt Threads has partnered with companies Stella McCartney and Best Made Co. to develop garments using Microsilk.

View Article Sources
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