How do I care for a black blade treatment on a ninjato sword?
Updated Feb 2026
Caring for a black blade treatment on a ninjato follows the same fundamental approach as any colored blade finish on high-carbon steel. After every handling session, wipe the full straight blade with a soft lint-free cloth to remove moisture and fingerprints - high-carbon steel beneath any color treatment will oxidize if left with moisture on the surface. Apply a very thin coat of camellia oil or mineral oil and buff away excess with a soft cloth. For the black surface treatment specifically, use only soft cloths for any contact and never use abrasive materials, metal polishing compounds, or solvents that would damage or remove the color. The straight ninjato blade makes the wiping routine particularly straightforward - the flat, uninterrupted surface can be wiped from spine to edge along the full length in a single smooth motion without navigating the katana's curve. Store the black ninjato in the scabbard or on a display rack in a low-humidity room to protect both blade and lacquered scabbard surfaces. Inspect periodically for any oxidation developing beneath or through the black treatment.