How is the hamon on a clay tempered T10 ninjato formed?
Updated Feb 2026
The hamon is created through differential hardening, a centuries-old Japanese technique. Before quenching, the smith applies a clay mixture — thicker along the spine and thinner along the edge. When the heated blade is plunged into water, the thinly coated edge cools rapidly and becomes extremely hard martensite, while the thickly coated spine cools slowly into softer pearlite. The visible boundary between these two crystalline structures is the hamon. Because variables like clay thickness, water temperature, and blade angle during quenching are never perfectly identical, every hamon pattern is unique. On T10 steel specifically, the tungsten content encourages a tight, well-defined transition zone that polishing reveals with particular clarity.