This is not a standard test performed on silk! However, it is a fairly definitive test. Extracted from the fabric edge off a bunch
of silk yarn, lit with a match. The bunch of Silk burn slowly with faint glow. Firstly, it will curl into a ball with a similar
smell of burning human hair or bird hair. Then, after burning into the dark brown globular, once you touch the globular,it will be
broken into powder. Finally, when leaving the flame, it stops burning immediately. So Silk is also a natural flame retardant .The
burning silk should smell like burning hair. (Both substances mainly consist of a fibrous protein–fibroin in the case of silk and
keratin in the case of hair.) A synthetic fabric will burn with a smell like burning plastic and will drip, form a black ball of
residue (not ash), and produce black smoke. It will continue to burn even after the flame is taken away.