 During silk comforter production, however, the silk filament is not unraveled, but rather stretched into a flat tangled web and layered to form silk floss, which will fill the comforter.The cocoons are first boiled to loosen the sericin holding the filaments together and kill the silkworm.Each cocoon is stretched by hand on a U-shaped wooden rack, and the ball of thread becomes a sheet of tangled fibers.