some years ago i watched one of our finest lampwork artists in UK, the late Diana East, creating an iridescent metallic lustre coating on a handmade bead by blowing "fumes" of gold onto the surface under heat , and also when visiting Czech beadmakers (with J-me and Guy) they were able to coat moulded faceted beads with a similar iridescent-metallic- type lustre also under heat within a sort of vacuum chamber. however that lustre tended to rub off the finished beads when worn on the skin!