What makes 1090 carbon steel stand out for katana collecting?
Updated Mar 2026
1090 carbon steel contains approximately 0.90% carbon, placing it in the high-carbon range that allows for meaningful differential hardening during the forging process. This heat-treatment technique creates a visible hamon - the temper line along the edge - that is a hallmark of authentic Japanese sword aesthetics. Lower-carbon steels and decorative stainless alloys typically cannot produce this effect. For collectors, the hamon is not purely cosmetic; it signals that the blade underwent a genuine hardening process rather than a surface treatment, which distinguishes a quality display replica from a mass-produced wall hanger.