How should I store a carbon steel katana to protect the finish?
Updated Mar 2026
Carbon steel is reactive to moisture and will develop surface oxidation if left unprotected. For long-term display, apply a light coat of choji oil or food-grade mineral oil to the blade before sheathing it in the saya - about once every four to six weeks, or more frequently in humid climates. Avoid storing the sword in a sealed case without any air circulation, as condensation can build up inside the saya. Keep the display away from direct sunlight; prolonged UV exposure can cause lacquered saya to fade or crack at the seams. When handling the blade for cleaning or repositioning, use clean cotton gloves to avoid transferring skin oils, which are mildly acidic and can leave marks on the gold finish over time.