Silk DOES burn when a flame is held to it.
Most textiles will burn readily, but silk only burns while a flame is held to it. Genuine silk fibers shrink from the flame and stop burning when the flame is removed. The authenticity of silk can be determined by an odor that has been compared to charred meat or burning feathers. Wool is another fiber that shrinks from the flame, but the odor produced is more similar to burnt hair. Other natural fibers such as cotton, ramie and hemp burn quickly and smell like burning paper. Synthetic fabrics produce a chemical odor as they burn and melt simultaneously.
How Silk is Made
Silk has long been considered a luxurious fabric used to make garments for people who have the ability to pay higher prices for their clothing. Silk is expensive because of the complicated process required to create the fabric. The silkworm creates a cocoon around its body by secreting a substance through its head. The cocoons are then softened by a series of immersions in hot and cold water, allowing the silk filaments to be unwound in one continuous strand. Up to 10 filaments are wound together to produce “reeled silk” in lengths from 300 to 600 m. These reeled filaments are then wound into skeins and shipped to silk mills in many areas of the world. The fabric made from silk can vary in appearance. Raw silk fabric may closely resemble cotton while fabric woven of very refined silk threads is lightweight and silky.
“FabricLink | Fabric University.” index.jpg. N.p., n.d. Web. 19 Oct. 2012. http://www.fabriclink.com/university/burntest.cfm
“How Silk is Made.” Silk Painting Gallery All About Silk Painting. N.p., n.d. Web. 19 Oct. 2012. http://www.silkpaintinggallery.com/silk.htm