Kosa silk is obtained from the Indian silkworm Antheraea mylitta and is a variety of Tussar silk. The silkworms grow their cocoons on specific kinds of trees, which include the varieties arjun, saja and sal. Kosa silk is known for its sturdiness and its unique texture.
Two places, namely Korba and Champa in Chhattisgarh, are known for producing high- quality Kosa silk. The one produced in Champa is known to be of superior quality and is exported around the world.
The production of a single meter of Kosa Silk is a painstaking process and becomes even more complicated due to the rarity of the Kosa worm. As a result, the raw silk yarn is mixed with cotton or polyester in many cases. A simple Kosa sari may take about three to five days to produce, starting from yarn extraction to weaving, depending on the number of people involved.
The best way to check the purity of Kosa Silk is by burning a few threads of the fabric. If authentic, the burnt threads leave a residue quite unlike ash, which is black in color and has an unpleasant odor.