1) Silk is a natural protein fiber secreted as a filament by silkworms. It is off-white to yellow in color with a diameter of 12-30 micrometers.
2) There are four main types of silk: mulberry, eri, tasar, and muga. Mulberry silk accounts for around 90% of world production.
3) Silk is composed mainly of the protein fibroin surrounded by the gumlike protein sericin. When processed, the sericin is removed, leaving nearly pure fibroin fiber.