Rosewood is naturally dense and oil-rich, which makes it more resistant to moisture than softer woods, but it still benefits from regular attention. Wipe the saya with a dry microfiber cloth after handling to remove fingerprint oils. Once or twice a year, apply a thin coat of natural wood conditioner — lemon oil or food-grade mineral oil works well — and buff it dry. Store the sword horizontally on a rack in a room with stable humidity, ideally between 40 and 55 percent relative humidity. Avoid placing it near heating vents or in direct sunlight, which can cause the wood to dry out and crack over time. With basic care, rosewood darkens to a rich, warm patina that improves the display appeal of the piece.