This is video of a tour we took of a silkworm factory in Đà Lạt, Vietnam. Below is a description of the stages in which silk is created and harvested from silkworms:
“The production of cocoon for their filament is called sericulture. The species Bombyx mori is usually cultivated and is raised under controlled condition of environment and nutrition. The life cycle of silkworm encircle in the four stages. The egg, the silkworm, the pupa and the moth. The silkworm which feeds on mulberry leaves forms a covering around it by secreting a protein like substance through its head. This stage is called cocoon, the desirable stage for the silk producers.
Filature operations: The cocoons raised by the farmer are delivered to the factory, called a filature, where the silk is unwound from the cocoons and the strands are collected into skeins. Some cocoons are scientifically bred in such factories. The filature operations consist of the following stages.
The cocoons are sorted according to the color, size, shape and texture as these affect the final quality of the silk. Cocoons may range from white and yellow to grayish.
Softening the Sericin:
Silk filament is a double strand of fibroin, which is held together by a gummy substance called sericin or silk gum. After the cocoon has been sorted, they are put through a series of hot and cold immersions, as the sericin must be softened to permit the unwinding of the filament as one continuous thread.
Reeling the filament:
Reeling is the process of unwinding the silk filaments from the cocoon and combining them together to make a thread of raw silk. As the filament of the cocoon is too fine for commercial use, three to ten strands are usually reeled at a time to produce the desired diameter of raw silk which is known as “reeled silk”. The useable length of reeled filament is 300 to 600 m.
The silk filament is reeled into skeins, which are packed in a small bundles called books, weighing 2 to 4.5 kg. These books are put into bales weighing about 60 kg. In this form raw silk is shipped to silk mills all over the world.”
—taken from a silk production website.