I was recently in Lyon in France, where they make beautiful silk luxury items, and I discovered some interesting facts about silk manufacturing that I’d like to share with you. As early as the 12th century, the Chinese were the first to produce silk. They used it to make winter clothes, bow-strings and fishing-nets since silk was a very cheap product there. It is a natural fibre produced by the caterpillar of the mulberry bombyx butterfly. The breeding of this silkworm is known as sericulture.
The stages of silk growth
The various stages necessary to the manufacture of the silk fibre are as follows: the eggs or seeds are round and very small, only a few millimetres in diameter. They are yellow when they are laid, then turn grey after a few days. The eggs are hatched artificially when the mulberry tree leaves appear. Before they hatch, the eggs are incubated by heating them gradually for a couple of weeks. For a long time, human body warmth was used for this: women carried seed bags on their chest or their belly. Nowadays electric incubators are used instead. When they are first born, the silkworms are black with hairy bodies and measure around 3 mm in length.
In the first thirty days, the silkworm grows to ten thousand times its initial weight and ends up between 6 to 8 cm long. It sheds its skin or moults four times. This period of growth requires close attention, the temperature needs to be carefully controlled and the breeders act almost like nannies. The larva needs specific food so that the silk filaments become solid, fine and elastic. It is fed the leaves of the mulberry tree three times a day. During the last week, the silkworm eats a lot more in preparation for the cocoon. On around the thirtieth day, its appetite slows down, and the silkworm starts to weave its cocoon with branches of heather deposited by the breeders. The worm turns on itself, its head making a figure of eight. The following day, it is put into storage for safekeeping. Over a short period of time the silkworm spits out between 800 and 1500 m of silk thread. 8-10 days later, the cocoons are unwound and then sorted into drying ovens at 70-80 degrees for around eight hours. In this way the larva is destroyed without damaging the cocoon. The silk fibres are then ready for spinning, either manually or mechanically. They are arranged and twisted to increase resistance and to take on the necessary properties.
Silk production in Lyon
In Lyon, silk production started in 1536 and became an industry when the first weaving machines were invented. Lyon’s silk industry was so popular that it began to export throughout the world. Shortly before the French Revolution, this thriving industry sustained more than half of the inhabitants of Lyon. Little by little, in the St Jean neighborhood, magnificent Renaissance style residences were built, a testimony to the extreme wealth of the merchants who acquired the silk and then sold it once it was woven. It was also at this time that weaving looms were set up where silk workers would spend hours making pieces of fabric for very little pay. Following the French Revolution, rioting silk workers and the invention of industrialised silk put an end to the golden age of the silk production in Lyon during the 19th century.
Uses of silk
Apart from its many clothing uses, silk’s attractive lustre and drape makes it suitable for many furnishing applications. It is used for upholstery, wall coverings, blended with other fibres for window treatments, rugs, bedding and wall hangings. Artificial fibres have largely replaced silk, but it has traditionally had many industrial and commercial uses, such as in parachutes, bicycle tyres, duvet filling and artillery gunpowder bags. New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms.