Silk fabric is made by collecting filaments from a mulberry silk moth's cocoon, combining the output from four to eight cocoons into a single strand of raw silk, washing and preparing the silk strands and then weaving or knitting the strands into fabric. Approximately 2,500 silkworms must work to produce a pound of raw silk.
Manufacturers produce four types of silk yarn. To make thrown singles for sheer fabrics, they twist individual strands in one direction. For tram that goes into the weft of a fabric or filling, they twist multiple strands in one direction. To produce crepe for crinkly fabrics, they twist raw silk threads, double them and twist again. To make organzine warp threads, manufacturers twist raw silk in one direction and then twist two strands together in the opposite direction. Each strand of silk measures 600 to 900 meters long.
As of 2005, the world's top silk producers were the People's Republic of China, India, Uzbekistan, Brazil, Iran, Thailand, Vietnam, the Democratic People's Republic of Korea, Romania and Japan. China cultivated 3.5 times more silk than second-place India.
Silk was first produced in China around 3000 B.C. Silk textiles have been found in ancient Chinese and Egyptian tombs.