Degumming Eri Silk Cocoon – An Important First Step to Spin Yarn

Welcome to studio Muezart, home to Eri silk

Muezart is based in Shillong, a city which is in the Northeast of India and also called the Scotland of the East.

Shillong, Scotland of the East

If you are on this page then, perhaps, you are looking for something more on Eri silk, which is also called peace silk?

Or are you a nature lover looking into the world of silkworms?

Or exploring options for organic, natural, yarn like Eri silk yarn to weave with?

Whatever the reason, we hope to see you benefit from this visit. We are here to share with you our knowledge of the world of Eri silk.

Muezart has first-hand experience in every step of Eri silk production, from silkworm rearing, to collecting the cocoons made by the Eri silk caterpillars, to spinning Eri silk yarn from these fibre-rich cocoons, to weaving with Eri silk yarn. We are happy to share our learnings with you.


Moth laying eggs

Hatched eggs

one week old silkworms

Cocoon spinning


In this post we want to tell you about degumming cocoons, which is an important first step in Eri silk processing.

While we are at it, we will pass on to you a few other pieces of info about Eri silk too, to make this a more complete post.

You know that silk fiber is obtained from silk cocoons, right? Have you seen a silk cocoon?

Here are a few cocoons of Mulberry silk and a few cocoons of Eri silk.

Mulberry left - Eri right

Both types of cocoons look like beads, do they not? Something you can string. Except that, they are soft and silky to the touch and not firm.

Look at them closely. What are the differences that you can spot?

The Mulberry silk cocoons look smaller, more even and rounder.

The Eri silk cocoons looks larger, more oval and each seem to be of a different size.

What else is the difference between the two?

The Mulberry cocoon looks whiter, while Eri silk cocoon looks creamish.

Mostly mulberry cocoons are bright white in color, though there are cream colored ones too. The Eri silk cocoons are either off-white in color or a little reddish.

Red eri and white eri cocoons

Interesting titbit 1:

The Eri silk cocoon of the male moth is smaller in size than the Eri silk cocoon of the female moth.



The cocoons are made by the Eri silkworms once they turn into full-grown caterpillars. Each caterpillar makes one cocoon.

Have you heard of the very popular kids’ story called the ‘The Very Hungry Caterpillar’ by Eric Carle? In that book the caterpillar eats an apple on Monday, two pears on Tuesday, three prunes and on Wednesday, and so on. At the end, the hungry caterpillar builds itself a cocoon, goes into hibernation and becomes a butterfly. This makes a super exciting story for kids.

The Eri silk caterpillar, on the other hand, life is different! It eats either castor leaves or cassava leaves for up to two to three weeks, spins itself a cocoon and hibernates for two weeks and emerges as an Eri silk moth. Once the moth leaves, the cocoons are collected to harvest the silk fiber.

Here is what the castor leaves look like in real time. (Watch this video)

Here is what a fully grown caterpillar looks like before it spins its cocoon
After the cocoons are collected, the degumming process starts

Here is a bunch of freshly collected Eri silk cocoons

An interesting titbit 2:

Did you know that the Mulberry silk cocoons are boiled in water with the moths inside? ☹. This is done to get a better quality of mulberry silk – to get longer strands.

On the other hand, the Eri silk moths are allowed to leave the cocoons before Eri silk fiber is spun into yarn. That is the reason Eri silk is called Peace silk.

What is degumming a cocoon?

As the word suggests – the process of removing a gummy substance from the cocoon is called degumming.

Why do we need to degum a cocoon?

When it is time to make the cocoon, the caterpillar goes into a production mode. It rotates its head with speed, in a shape of ‘8’ and throws out a fiber from its mouth. It spits it out - in a continuous stream. What it ejects is silk fiber. There is a gummy substance in these strands that helps them to stick together and form the cocoon. The caterpillar rotates its head to get the shape of the cocoon right. Is that not a true wonder of nature? Remember, the ejection from its mouth happens without a break till the cocoon is fully formed. It is not like the caterpillar takes a break once in a while! Talk about diligence and hard work.

An interesting, but sad, titbit 3:

One terribly sad bit of trivia – once the caterpillar builds its own cocoon, it stops eating. So, after all the hard work it starves for days till it becomes a moth. The worst bit of news is the silk moths do not have mouth parts and so cannot eat ☹. The Eri moths live for less than 10 days and before they die, they procreate, making 300 to 400 eggs. Don’t look for ‘right’ and ‘wrong’ or ‘this should or shouldn’t be’. This is how nature has meant it to be. Amen.

An eri silk moth
Let us get back to the degumming question. Why do we need to degum a cocoon?

All silk fibers are made of two proteins – Sericin and Fibroin. Fibroin is the interior protein and Sericin, the outer gummy protein that helps the fibers to stick together, giving the cocoon its structural integrity. Sericin, a very gummy substance, has to be washed off so that the strings of the fiber can be separated. Only when the strands are separate, can we spin the silk yarn.

Hence degumming is an important first step in Eri silk spinning.
The degummed cocoons are stretched and flattened and dried. Eri silk yarn can be spun directly from a fluffed cocoon.

Here is a video made by Muezart where Peter explains what a Cocoon is and Rida shows us - 'how to fluff a cocoon'.

A few more titbits 4:

Once the Sericin is degummed, the cocoon is left with a bright white fibroin.

Fibroin refracts and reflects light, giving silk its lustre and allows it to absorb dyes more vibrantly. Muezart team dyes only with natural dyes.

The exciting thing about Sericin is that it’s a BOON for the beauty and skincare industry, while its considered waste in the textile industry.

Why?

Cream with sericin is used for topical skincare application; as anti-ageing, anti-wrinkle cream; to smoothen the skin; and to enhance the skin elasticity.

So, the next time you're in a beauty shop check out products that contain Sericin.

Who knows using sericin cream might make you end up looking forever young 😊

How are silk cocoons degummed?

  1. Fill a vessel with water and bring to boil. The quantity of water depends on the quantity of cocoons you want to degum
  2. Add ½ cup of an alkaline soap for 100 cocoons. Do not use detergent
  3. Simmer for an hour or so. Do not allow to boil as cocoons may tangle up
  4. Wash the cocoons till water runs clear. Stretch the cocoons and hang to dry. Once dry you should be able to pull the strands apart and fluff them. If this is not happening, then repeat the degumming process

You can see how to fluff the cocoons in the video posted above.

Do you want to see an experiment Muezart conducted to test if soap nut berries could be used to degum Eri silk cocoons? Watch

Hope we helped you to understand the ‘why’ and the ‘how’ behind degumming of silk cocoons?

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