The most important of the silk-spinning insects is the real silk moth.
The Bombyx mori silkworm has been bred on trays of mulberry leaves (hence the name "mulberry silk moth") in China for almost 5000 years. Long before the rise of the Roman Empire, when the tribes of Europe still lived in primitive huts, the silkworm was already fully domesticated.
For millennia, it has not been able to survive without human care and feeding. There are no wild mulberry silk moths or moths living in the wild.
Raised in captivity for thousands of years, the silk moth Bombyx mori has evolved into a blind moth that cannot fly and only lives for a few days. During this time, he lays about 400 eggs and dies after four to five days. The moth has no eating tools and cannot eat any food. Silk farming usually takes place in large industrial plants. In the last few decades, silk has degenerated into a mass product without appreciation. The enormous drop in prices and the concentration on economically efficient large companies have not only damaged the quality, but also worsened the cultivation conditions for the silk farmers and polluted the environment.
Silk farming in India
In India live mainly the Japanese oak silk moth Antheraea yamamai and Eri and Muga silkworms. Traditionally, wild collection is based in India. The cocoons left by the butterflies in the forests and are collected for further processing. As part of programs to generate income for the poor rural population, small agricultural projects in which the Tussah silk moth is bred have emerged in many states in recent years. Therefore, the description of Tussah silk as "wild silk" is no longer correct today. Influenced by the past of wild collection of cocoons and the philosophy of non-violence, e.g. by Mahatma Gandhi, silk farming is often practiced in the spirit of "Ahimsa" (sankskrit: non-injury).
Two methods are mainly used. On one hand, the cocoons of the silkworms are not processed until the moth has hatched. The cocoon is dissolved by the moth with endogenous fluids. A hole is etched into it for the moth to escape through. So the cocoon is damaged and it is no longer possible to unwind a filament. The relatively short pieces of thread must first be spun to enable further processing (in the weaving mill). The traditional wild silk fabrics made from tussah silk were also created using this method.
With the Tussah silk breeding of the Japanese oak silk moth, it is possible to provide the completed cocoons with a small incision and then leave them to continue their natural development. The moth "discovers" the hole created for it and escapes without further damaging the cocoon. This method of silk fiber extraction is more effective in terms of the quality of the silk fibers.
Some of the silk is processed in small, handicraft businesses, where individual silk fabrics are created on hand looms, some of which are also spun by hand.
The differences in textile fabrics
To obtain mulberry silk (formerly: cultivated silk), the cocoons are dried when abandoned by the silkworm after they have hatched. In the first step of the processing, the cocoons are softened in a hot alkaline solution in order to loosen the sericin, the silk glue, and to be able to unwind the silk thread. A continuous thread up to 1500 m long can be won from a cocoon (reel silk). From inferior or damaged parts of the cocoon, the short fibers are processed into Schappeseide (spider silk).
The thread of the mulberry silk moth is a very fine and regular fibre, due to five millennia of cultivation. After removing the sericin, the filament (the grège) is nearly white. Fabrics made from mulberry silk have a strong luster, are smooth to the touch and drape soft and supple. They correspond to the usual idea of a silk fabric.
With wild collection or the Ahimsa method, it is not possible to reel off endless filaments because the cocoons have been damaged by moths or humans. This means that only relatively short fibers can be obtained, which then have to be spun so that a textile can be woven from them. Furthermore, the "Indian" silkworms have in common that their silk threads have a yellowish to brownish color and are also much more irregular. This resulted in the typical wild silk structure.
If the silk fibers are degummed well and spun into fine yarns, the result is very soft and tactile fabrics with interesting textures. This is reinforced by the spinning and weaving techniques of manual production, which are difficult to replicate industrially. The three types of silk Tussah, Eri and Muga are often mixed in order to vary the fabric properties. Tussah silk fabrics are less lustrous, heavier and more "sturdy" than mulberry silk fabrics.
Ecological and social aspects
If silk farming is carried out as organic or bio-dynamic agriculture and the corresponding criteria are met, certification according to EU 834/2007, the so-called organic regulation, as "controlled organic animal husbandry" (kbT) can take place. The fodder for the caterpillars is cultivated without herbicides and pesticides and the animals are kept without hormones and the use of other chemical agents. Raw silk production, reeling and boiling must also be kbT-compliant.
The raw silk can then be processed into textile fabrics according to the rules of the Global Organic Textile Standard (GOTS) or the IVN Best certification. With these two seals of quality, ecological, sustainable and social parameters are included in the assessment.
The standards define the list of possible substances that may be used in the entire textile chain, which waste water qualities must be met and that fair working conditions must be observed. The core labor standards of the International Labor Organization (ILO) form the basis for the social parameters.
Regular quality and residue controls are just as obligatory for obtaining one of the two certificates as the complete documentation and traceability of the end product back to its origin (traceability). This ensures that the consumer is holding a textile in their hands that was actually manufactured under fair, ecological and sustainable criteria.
In addition to the incomparable properties and the attractive charisma of the natural fiber silk, this means that the wearer or buyer can afford the luxury of an exclusive piece of clothing with a clear conscience. Whether it's organic silk or Ahimsa silk - that's up to personal taste.
© Dr. Matias Langer 2014
Note on organic silk pricing
The higher price of organic and non-violent silk (organic and Ahimsa silk) compared to conventionally produced silk is caused by
- lower yield due to smaller but higher quality cocoons with organic feeding and breeding
- higher production costs due to lower production quantities (scaling effect) and ecologically compatible treatment and processing (spinning, twisting, weaving, dyeing)
- higher wage costs through social and fair working conditions
- additional cost of annual certification