There are too many mischaracterizations to address individually in the last post; needless to say, steel itself is primarily iron with only trace elements added, such as varying amounts of carbon (usually less than 1%) and other elements. Color of the steel does not rely on polishing but is inherent in the material. Even though the tatara method does not result in complete melting, there is sufficient fusion to result in varying trace elements to be incorporated based on material inputs. These cannot be visually identified by the smith; the smith sorts materials based on their characteristics before and after being heated and quenched, then broken. Higher carbon materials break under those conditions, while low and medium carbon materials are more resilient. There is a lot more to say but I am sure Ken can contribute a LOT.