What makes a tsuba 'black' — is it a coating or the metal itself?
Updated Mar 2026
The answer varies by piece. Traditional Japanese iron tsuba develop a natural dark patina through controlled oxidation — a process called rokusho treatment or simple oil-and-heat cycling — that produces a stable, matte black or dark grey surface that is part of the metal itself, not a surface layer that can chip or peel. Modern production pieces more commonly use a black oxide finish, a chemical conversion coating that bonds to the iron at the molecular level and provides similar visual results with good durability. Some decorative tsuba use a lacquer layer over iron or steel for a glossier appearance. For display purposes, all three are stable choices, but oil-patinated iron develops the most character over time, deepening slightly with age and handling.