Ferric chloride was used by Oscar as part of his etch for damascus.He also experimented with dilute sulphuric acid. He refers to it in both his 1997 article and the last one in DGJ. The purpose of the Ferric Chloride is to etch the iron and turn it black, the rusting process occurs after the etch, and the finishing is done with the boiling logwood bath. This gives the classic Black/White of American SxS's. All of Oscar's articles are available from DGJ. Still, even with Oscar's detailed "menu" it is more "art" than "science". Best, Dr. BILL