What is Hadatatsu in Japanese Katana terminology?

Hadatatsu or 肌立つ in Japanese, refers to a state where the forged parts of the ground iron (jigane) of a Japanese sword are prominently visible. This occurs as a result of the ""Orimodoshi Tanren"" (折り返し鍛錬), a process of repeated folding and forging that is used to make the sword.

The term ""Hadatatsu"" literally translates to ""skin standing"", which describes the appearance of the pattern that stands out on the surface of the sword. This pattern is a testament to the meticulous forging process that the sword undergoes.

The pattern of the ground iron (jigane) plays a significant role in the aesthetics and value of a Japanese sword. It is one of the factors that sword connoisseurs look at when evaluating a sword. The Hadatatsu, with its prominently visible forged parts, is a distinctive feature that sets the sword apart.