The Ultimate Guide: Mulberry Silk Production 101

Perhaps the most striking, soft, and lustrous fabrics ever made. Mulberry Silk can be dated back to thousands of years, and still to this day is vastly considered as one of the most esteemed, expensive materials. But how was this stunning fabric discovered? How is it produced? Well, even after all of those centuries, little has changed in the way silk is created. After all the technological advances in the production process of silk in the modern ages, silk production still desperately remains a labor-exhaustive procedure, and a significant amount of heavy labor is still involved.

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So, to know and understand the history, the production, and functional uses of Mulberry Silk, just keep on reading.

History of Silk

The word silk originates from ancient English “Sioloc” which roughly translates to “silken.” Silk is a natural protein fiber that is extracted from insects that can be entwined to become textiles. Silk protein fibers are composed mainly of fibroin and are produced by insect larvae precisely for the formation of cocoons. The most well-known silk captive mulberry silkworm which is observed in the larvae cocoon of Bombyx mori.

• China

  During the Neolithic period, the production of Silk first began in ancient China. During the Yangshao culture in the 4th millennium BC, this practice of silk-making eventually widely extended to the lands of China. Moreover, silk use in fabric was first established also in ancient China. Scientists discovered silk protein fibroin from landfills in tombs at the neolithic site Jiahu in Henan. This discovery is considered the earliest proof of silk usage, which dates back approximately 8,500 years ago.

  Furthermore, the primitive persisting piece of silk fabric originated from about 3630 BC. It was utilized as the enfolding for a child's body at a Yangshao culture site in Qingtaicun near Xingyang Henan. Silk production persisted in China for years. The silk road has led to the shift in the persistence of output in China. Although, through this period, China upheld its implicit control over silk production for another thousand years.

  In China, it is well known that people give credit for developing Silk to a Chinese empress, Lei Tzu. During this period, silks were firstly reserved for the Emperors of China for their usage and gifts to other loyalties. To keep Chinese ownership, the leaders of Ancient China tried to keep knowledge of sericulture a secret. However, this eventually spread through Chinese culture and trade both geographically and communally and then extended to several regions in Asia. Silk quickly became an admired luxury fabric in numerous areas reachable by Chinese merchants because of its texture and sheen. The silk trade reached far lands across Asia, Africa, and Europe. Business trades in these regions became widely extensive that the trades routes came to be known as the Silk Road. People had a great interest in Silk which increased its demand and became a staple in pre-industrial international trade. In addition to that, during the Warring States period, Silk was also utilized as a surface for writing. The fabric was light, and it endured the moist environment of the Yangtze state, absorbed ink well, and offered a white background for the text. Furthermore, Silk was also described in the old writings of China. These ancient documents include a chapter of the Fan Shengzhi shu from the Western Han.

  Silk from China was the most profitable and coveted luxury item exported across the Eurasian continent in the old age. Many cultures, such as the ancient Persians, profited economically from such trade.

   

• Europe

  Italy was considered the main producer of Silk in the Medieval period. During the 11th century in Calabria, the first region to pioneer Silk production was Catanzaro City. Silk produced in Catanzaro supplied practically almost all areas in Europe. In addition, in the harbor of Reggio Calabria, silk makers of Catanzaro were also able to trade Silk to merchants from Spain, Venice, Geneva, and the Netherlands. In a few years, Catanzaro was considered the lace capital of the world because of its enormous silkworm breeding facilities that produced all the silk linens used in Vatican city.

  The City-State of Lucca was also another vital silk producer in Europe during the 12th century. This region was able to sustain itself through silk production and silk trading. Other places in Italy in the silk production market were Florence, Genoa, and Venice. Silk was also manufactured in and distributed from Granada, Spain, particularly the Alpujarras area, until the Moriscos, whose industry it was, were barred from Granada in 1571. Finally, in the 15th century, silk production in France became centered around the city of Lyon. In the 17th century, Lyon was introduced with several machine tools for the mass production of Silk.

  A few years later, King James I struggled to institute Silk production in England. He purchased hectares of land and was instructed to plant about 100,000 mulberry trees. However, the Species that grew in the area were incompatible with the silkworms, and his attempt to produce Silk was unsuccessful.

  In 1732, a silk-throwing business began under the entrepreneurship of John Guardivaglio. He set up an enterprise in Stockport. Sometime later, in 1744, silk production under Burton Mill started in the town of Macclesfield. Finally, in 1753, Old Mill was constructed in the town of Congleton. Until silk throwing was substituted by silk waste spinning, these three towns stayed the center of the English silk throwing industry. In 1928, British enterprises also established silk filature in Cyprus. In England in the mid-20th century, Lullingstone Castle in Kent was responsible for producing raw Silk. Under the supervision of Zoe Lady Hart Dyke, silkworms were nurtured and harvested. In 1956, the production then moved to Ayot St Lawrence in Hertfordshire.

   

• United States of America

  Researchers have discovered that the Aztecs utilized wild silk taken from the nests of native caterpillars to build containers and papers. According to historical facts, silkworms were first presented to Oaxaca from Spain in the 1530s. The state benefited from silk production until the early 17th century, when the king of Spain prohibited the distribution of silk from protecting Spain's silk industry. Nevertheless, silk production for local consumption has continued until today, sometimes spinning wild silk.

  The Shakers in Kentucky adopted the practice of Silk-growing following the introduction of King James I to his British colonies in America around 1619, supposedly to dissuade tobacco planting.

  In the United States, The history of industrial silk is mostly linked to several minor urban centers in the Northeast region. When Cheney Brothers correctly nurtured silkworms on an industrial scale, Manchester, Connecticut, became the primary center of the silk industry in America beginning in the 1830s. With the increasing mulberry tree obsession during that period, other smaller manufacturers started raising silkworms. This economy predominantly got traction in Northampton, Massachusetts, and its neighboring Williamsburg, where many small firms and cooperatives developed. Among the most noticeable was the cooperative utopian Northampton Association for Education and Industry.

  In 1874, Following the devastating Mill River Flood, one producer, William Skinner, moved his mill from Williamsburg to Holyoke. William Skinner and his sons would continue associations between the American silk industry and its counterparts in Japan over the next 50 years. They expanded their business until, in 1911, the Skinner Mill complex became the largest silk mill under one roof in the world. Globally, Skinner Fabrics had become the largest producer of silk satins.

  However, World War II disturbed the silk trade from Asia, and silk prices increased severely. As a result, the U.S. silk industry started to look for alternatives, which led to synthetics, including nylon. These synthetic silks are produced from lyocell, a type of cellulose fiber that is frequently compared to real silk.

   

• Where Does “Mulberry” Silk Name Come From?

  Mulberry is known as the silkworm tree. As stated above, the production process of Silk, also called sericulture, became widespread and famous thousands of years ago in ancient China. Being prominent in a few regions in China, Mulberry trees were an ideal and great food source for caterpillars. After scrutiny, the Mulberry leaves seemed to be silkworm’s preferred food. The local population in ancient China came up with the idea that having more Mulberry trees entices more silkworms, therefore letting them create more of the valuable Silk. With the expanding popularity of Silk in the world, the production required to be supervised, and the silkworms began to be domesticated. In modern times, studies have shown that silkworms are attracted to cis-jasmone, which is a natural odorant produced by the Mulberry. This reason is why Silkworms prefer to feed on the tree. This is where the name Mulberry silk came from.

Process of Production: Step by Step Guide

Today, the industrial production of silk greatly relies on cultivation of silkworms. The commercial production of silk, also known as sericulture, is an extensive and intricate process involving a wide range of skilled people at various stages of its production. Around the world, thousands of people are occupied in numerous sericulture activities throughout the year. 

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Throughout the years since its discovery and development in ancient China, the traditional way of producing silk has not changed a lot, even with technological advancement. That is the main reason why it is still laborious and requires a lot of time. This technique involves the assistance of the larvae form of certain silkworm species. With that, in order to become more familiar and knowledge on the production of silk, here is an outline of the different steps involved in the production of mulberry silk:

1. Sericulture or Cultivation

   Mulberry cultivation, known as sericulture, gathers and grows silkworms and harvests their cocoons to gather ample ingredients needed to produce silk.

   Silk farmers harvest fresh, soft, and tender mulberry leaves. These leaves are then placed in a flat tray. Almost 500 eggs are laid at one time by a female Silkmoth. These eggs eventually hatch to form silkworms, nurtured in a controlled environment until they hatch into larvae or caterpillars.

   The silkworms are fed incessantly with many mulberry leaves to encourage their growth. It usually takes about six weeks to grow to its full potential. The ideal length of a silkworm is approximately 3 inches. When this length is reached, silkworms are considered more than 10,000 times heavier than their initial weight. Also, when the ideal weight has been reached, silkworms will stop eating and begin to raise their heads. This raising of the head indicated the readiness of silkworms to spin their cocoon.

   Silkworms then attach to a secure frame or tree. Next, the silkworm will spin its silk cocoon by rotating its body in a figure-8 movement around 300,000 times. The whole process takes around 3 to 7 days. A spinneret, an opening in the head, will move to release the liquid silk produced by the silkworm's glands. Liquid silk solidifies when exposed to air due to its protective coating known as sericin. Each silkworm produces just one strand of silk, which measures about 100 meters long and is held together by sericin.

    

2. Stifling and Sorting

   The silkworms will surround themselves with the silk strand they made after completing the spinning process. For the pupas not to hatch and break the silk cocoons, they must undergo stifling or the operation of subjecting the cocoons to steam or gas. This technique will also aid in drying out the cocoons to preserve them longer.

   After stifling, the cocoons have to be sorted out based on quality and other features, including color, shape, length, and luster. Cocoons with flaws such as mold growth, urine stains, and perforations would be discarded.

    

3. Water Boiling

   To aid in the softening of the cocoons, they are placed in boiling water. This boiling method also allows silk producers to easily locate the end of the fiber strand required for unwinding. In addition, boiling also breaks down the cocoon adhesive known as sericin without damaging the fibers and guaranteeing the gathered threads are intact. Since it can make the silk rough and difficult to dye, gum removal is of utmost importance.

    

4. Deflossing

   Immediately following the boiling process, the cocoons may still have loose fibers or an ill-defined layer that holds uneven and broken filaments. Deflossing must be performed in cocoons to remove these filaments. This process produces a cleaner look, easier next methods, and better market value. The deflossing process involves brushing or peeling off the layer manually.

    

5. Reeling and Twisting

   After deflossing, it is important to unroll the cocoon and combine the silk filament to turn the cocoons into threads and produce a single silk strand. This step is known as reeling and twisting. Traditionally, this step was done by hand. However, today, silk producers utilize machines that simultaneously unravel and dry the silk. During this step, a small amount of sericin may remain on the threads, protecting the fibers during processing; however, this is usually washed out with soap and boiling water.

   In addition to that, many producers reel several filaments together since one silk strand is too thin. Depending on how thick the final silk yarn will be, about 2 to 20 cocoons are spun together to produce the product. After that reeling, the next step is to detach the string from the reel and then twist it into spiral circles, forming skeins or bundles of yarns. The number of twisting and silk threads utilized will greatly depend on the types of silk the manufacturer aims to make.

    

6. Dyeing

   After the washing and degumming of Silk, bleaching and drying will be done. After that, the dyeing process can now begin.

    

   • Traditional

     The traditional silk dyeing method utilizes natural colorings found in the surrounding environment, such as dyes of fruit or indigo plant leaves. A container with hot water and indigo leaves will be prepared to soal silk threads together in bundles. This procedure will happen numerous times to guarantee appropriate color tone and quality.

     However, with the advent of technology in the commercial manufacturing of silk, these traditional dyeing methods have almost become nonexistent. Today, most manufacturers utilize several dyes, such as acid dyes or reactive dyes. These dyes provide a more range of choices in colors and shades to serve the broader demand of customers.

   • Modern

     As stated above, technological advancement allowed silk producers to dye silk threads for a broader range of colors and shades. The modern dyeing process involves reactive or acid dyes that are easy to use, vivid, wet-fast, and have significant applicability. However, the issue with these stains is that they require several supporting agents, yield substantial quantities of wastewater, and have little dyeability.

     The modern dyeing process is nearly comparable to the traditional method, wherein the manufacturers immerse the silk threads in a dye bath. Although, the silk thread can either be fixed to a circular-shaped jig or fed through two cylinders.

      

7. Making silk heavier

   In this step, treatment utilizing synthetic resins and heavy metal salts must be done to produce weighted silk. Some producers also supplement dyes to color the threads. This treatment technique will aid in making the silk heavier, which is a more luxurious type of silk in the market.

    

8. Spinning step

   This spinning method has always been a crucial element in silk production. This step was traditionally done manually using the classic spinning wheel. However, modern industrial techniques have paved the way for manufacturers to spin silk threads much more rapidly. This quicker production method can be achieved through ring-spinning, mule-spinning, or hand-spinning. In addition, the spinning process helps unwind the dyed silk fibers to lay flat in preparation for weaving.

    

9. Weaving

   The final piece of silk that comes together is achieved through weaving. Today, there are several different methods by which silk can be woven. The most common ones are plain, twill, and satin. Also, the finish of the silk will greatly depend on the type of weave.

   Commonly, weaving encompasses entwining two sets of threads so that they lock around each other and produce a durable, uniform piece of fabric. The silk threads will be woven at right angles to each other, and the two different grades are called a warp and a weft. The warp will run up and down the fabric while the weft runs across it.

    

10. Digital or Screen Printing

    After weaving the mulberry silk, if a silk fabric needs a unique pattern or design, it will be printed after pre-treatment. Today, this process can be performed in two various ways:

    1. Digital Printing that utilizes a specially designed textile printer, using ink to transfer hand-drawn or digitally produced artwork onto fabrics; and
    2. Screen Printing is the more traditional, more hands-on technique of effectively producing the same outcome. However, in some situations, a silk product that is bolder and more radiant may be achieved due to a thicker application of ink.

     

11. Finishing

    Lastly, silks must be finished to be ready for use and market. Finishing a piece of silk offers it that exceedingly radiant sheen that it is so universally known. Finishing also helps in achieving the preferred appearance and feel of silk.

    Silk finishing can be done in many different ways, primarily by employing various chemical treatments which can augment a host of valuable properties such as fire resistance and crease-proofing.

How is Cruelty-Free Silk Made?

A long history of debate regarding the conventional method of producing silk has long been in place. The issue of land controversies lies in the idea of animal cruelty, primarily because of subjecting the silkworms to gas or heat and boiling them while they are still alive in the cocoon. 

With that, today, there are cruelty-free silk products in the market. However, the process does not involve mulberry silkworms but frequently consists of the silkworm Philosamia rinini. Unlike the traditional technique, silk cocoons are acquired and treated after the moth hatches from its cocoon. First, the moth will discharge a liquid that will aid in producing a hole where it will hatch and then disrupt the long, continuous silk fiber to make short ones. The next processes begin from spinning to finishing.

Though it is a cruelty-free technique, the silk created is somewhat more costly. This higher price is because of the extra ten days required for the larvae to grow and hatch. Furthermore, the cocoons only make about one-sixth of the usual fiber volume. This process of making silk is still not free of disagreements since the silkworms still experience some form of suffering. Some claim that these silkworms do not get enough food and are forced out of their cocoons prematurely. Others also accuse that the female moths might be compressed to death. On the other hand, the males frequently get refrigerated and released when needed for breeding and discarded when they can no longer mate.

• Physical

  A triangular cross-section with round corners is the typical structure of silk fibers made from Bombyx mori silkworm. This structure is mainly composed of beta-sheets. It is also composed of flat planes that allow light to be redirected and scattered, giving silk its natural gloss.

  The cross-section structure comes in different shapes and diameters for other types of silkworms, depending on the environment they thrive. For example, the cross-section for Anaphe is crescent-like, while Tussah is an elongated wedge.

  Silkworm fibers are naturally squeezed out from two silkworm glands as a pair of primary filaments glued together, with sericin proteins that function like adhesive, to produce what is known as bave. Natural and synthetic silk is recognized to have noticeable piezoelectric properties in proteins, perhaps due to its molecular structure. Therefore, silkworm silk was utilized as the standard for the denier, a measurement of linear density in fibers.

  Unlike many synthetic fibers, silk has a smooth, soft texture that is not slippery. Furthermore, silk is one of the strongest natural fibers, but it decreases its strength by 20% when wet. Silk is also widely popular for its excellent moisture to regain about 11%. However, its elasticity is moderate to poor: if stretched even a small amount, it remains stretched. In addition to that, it can be weakened if exposed to too much sunlight. Insects may also be attacked, particularly if silk is not cleaned properly.

  Silk also has been recognized as a poor conductor of electricity and hence susceptible to static cling. In addition, silk has a high emissivity for infrared light, making it feel cool to the touch. Shrinking of silk for up to 8% may occur due to a relaxation of the fiber macrostructure. So, silk must always be washed before garment construction or dry cleaned. Dry cleaning may still shrink the chiffon up to 4%. Infrequently, this shrinkage can be undone by a tender steaming with a press cloth. There is almost no gradual shrinkage or shrinkage due to molecular-level deformation.

• Chemical

  Silk produced by the silkworm contains two main proteins, Sericin and fibroin, fibroin being the structural center of the silk, and Sericin being the adhesive material surrounding it. Fibroin is made up of amino acids that form beta-pleated sheets. The high proportion of glycine amino acid of fibroin permits tight packing. Alanine and serine also make the silk fibers durable and resilient to breaking. This tensile strength is because of the numerous interceded hydrogen bonds, and when stretched, the force is applied to these multiple bonds, and they do not break. Silk resists most mineral acids, except sulfuric acid, which liquifies it. As a result, it is yellowed by perspiration. Chlorine bleach will also damage silk fabrics.

Uses of Mulberry Silk

Mulberry silk is widely accepted and sought-after in the market. Not only because it looks and feels expensive but also because silk can be used for several purposes.

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Today, mulberry silk has been increasingly famous in the bedding industry because of its natural properties. Mulberry Silk aids in generating an incredibly comfortable sleeping experience. Mulberry Silk can balance the body temperature and moisture throughout the night to support an ideal sleeping environment. With that, the bedding and beauty industry has marketed pillows or pillowcases, eye masks, silk comforters, and many more.

Besides being used in the bedding industry, silk is also well known in the fashion industry. It is used to make couture, everyday wear, and many other things. Because of its smooth feel and expensive look, together with its amazing temperature regulating abilities and advantages for skin and hair health, many people invest in silk wear, even though they may cost a little bit extra.

Why is Mulberry Silk Expensive? 

The physical and chemical properties of silkworms are required to protect themselves in the cocoon against harsh environments. In addition, the silkworm makes a fire, mite, and weather-resistant house to permit its metamorphosis. These properties are what make Mulberry Silk so luxurious. They provide a great advantage in skin, hair, and overall well-being. Being very strong, Mulberry Silk can be likened to a luxurious cocoon made by the finest silkworms.

As stated above, the complexity of the production process does not halt Mulberry Silk from being admired. However, why is that? The answer is relatively simple: Mulberry Silk threads are smoother, stronger, and finer than any other variety of Silk in the world. Studies have shown that Mulberry Silk is stronger than steel with the same diameter. In addition to that, Mulberry Silk also has a lower density compared to cotton and wool. It gives it the capability to hold as much as a third of its weight in moisture without feeling damp. Silkworm also produces a homogeneously colored cocoon containing the longest Silk threads available. It is a vital characteristic of spinning them together to create the finest type of Silk—making Mulberry Silk durable and high in quality.

Ethics of Sericulture

If you have reached the end of this article, you perhaps know by now that Silk is the result of an indispensable part of the caterpillar's metamorphosis. Unfortunately, for the traditional aspect of the industry, producing Silk means killing the silkworms within their cocoons. However, there is an ethical workaround to a thousand-year-old process: Peace Silk or Ahimsā Silk. When selecting products respecting this principle, one should save the life of silkworms. Moreover, this principle also ensures that the Mulberry trees are grown in an organic environment. Finally, Protecting the environment and workers should never be compromised for any market. Hence, it should always be of the utmost importance.

References: 

 

1. AdvanceTextile86. 2017. Silk Production Process Steps. Retrieved from: https://advancetextile86.blogspot.com/2021/08/silk-production-process-steps.html. Retrieved on 9 November 2021. 
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