
In sword and knife making, the hamon (刃文, hamon) (from Japanese, literally “blade pattern”) is the visual effect of differential tempering. The hamon is the visual separation between the hardened edge and the softer portions of the blade. In the case of a traditional Japanese clay hardening (Yaki-Tre), the process is be better termed ‘differential hardening’ as it is achieved during the quench / hardening of the blade. A similar effect can also be achieved in the tempering stage by deferentially heating the spine. The term ‘differential temper’ references the result of each method, while the term ‘differential tempering’ refers to the method used. For this discussion, we will focus on clay hardening.