The Key Role of Impurities in Ancient Damascus Steel Blades

"The art of producing the famous 16-18th century Damascus steel blades found in many museums was lost long ago. Recently, however, research has established strong evidence supporting the theory that the distinct surface patterns on these blades result from a carbide-banding phenomenon produced by the microsegregation of minor amounts of carbide-forming elements present in the wootz ingots from which the blades were forged. Further, it is likely that wootz Damascus blades with damascene patterns may have been produced only from wootz ingots supplied from those regions of India having appropriate impurity-containing ore deposits. "

http://www.tms.org/pubs/journals/JOM/9809/Verhoeven-9809.html