Why are some blades in this collection tinted red?
Updated Feb 2026
The red coloring on certain ninjato blades is achieved through controlled oxidation or acid-etching processes applied after the steel is shaped and polished. Some smiths use a heated chemical bath that deposits a thin, stable oxide layer on the surface, producing a deep crimson tone without affecting the steel's underlying hardness. Others employ selective acid treatments that darken the steel to a reddish hue while simultaneously revealing the grain pattern beneath. The result is purely aesthetic — it gives the blade a dramatic look that pairs naturally with darkred saya lacquer and complements themed displays. The coating is stable under normal indoor conditions, though a light application of choji oil every few months will help preserve the finish.