9

The back of the blade and the adjacent sides should be shiny (there are katas which you use your katana to make sure no one is behind you by using the mirror-like surface of the sword), but the center and edge may be more matte (but still reasonably polished) and should have a wood-like 'grain' or water-like pattern (think ripples or waves). These patterns are unique to each blade (if genuine and not etched) and are a major part of a particular blade's beauty and personality. In ancient blades the pattern forms as a result of the layering and forging process, but in modern blades it may be 'fake' and a result of acid etching.