How should I store and maintain a blue-finished carbon steel ninjato?
Updated Mar 2026
Carbon steel, regardless of surface treatment, is susceptible to rust when exposed to moisture, fingerprint oils, or fluctuating humidity. For a blue-finished 1095 ninjato, the recommended routine is straightforward: wipe the blade with a clean, lint-free cloth after any handling to remove oils transferred from skin contact, then apply a very thin, even coat of choji oil or a comparable mineral-based blade oil using a dedicated applicator cloth. The blue surface finish provides some inherent protection, but it should not be treated as maintenance-free. Store the ninjato horizontally on a display stand or in its saya in a climate-controlled environment away from direct sunlight, which can affect both the lacquer on the saya and the tonal qualities of the blue finish over time. Avoid storing in sealed cases without any air circulation, as trapped humidity accelerates oxidation even on treated surfaces.