Iridescent Stainless Cutlery Set

Iridescent stainless cutlery · Oxide coloring · Nakano Kagaku · Tsubame, Niigata

Color that lives inside the metal
IROAI's colors are not applied to the surface — they emerge from within it. The technique is called oxide coloring: by precisely controlling the thickness of the naturally occurring transparent oxide film on stainless steel (between 0.1 and 0.3 microns — roughly one ten-thousandth of a millimeter), different wavelengths of light are reflected or cancelled. The result is iridescent color, shifting subtly with the angle of view — the same optical principle that makes a soap bubble appear to glow with multiple colors at once.

Color without dye or paint — safe, stable, and recyclable

Because the color is structural rather than applied, it does not peel, fade under UV exposure, or degrade over time. The pieces can be recycled at end of life in the same way as any other stainless steel product — no separation of coating or treatment is required.

Two finishes — two different qualities of light

Mirror
The metal surface is polished to a mirror finish by craftspeople in Tsubame-Sanjo, Niigata — Japan's foremost cutlery manufacturing region. The oxide coloring is then applied over this reflective base, producing colors that appear light and luminous, shifting like a rainbow across the surface. Smooth to the touch at the lip.

Mirror — Blue

Matte
A proprietary surface treatment creates a fine matte texture before the oxide coloring is applied. The result is deeper, quieter color — the same hues read with more depth and less flash. Works equally well alongside natural wood tableware, lacquerware, or contemporary ceramics.

Matte — Blue

IROAI Matte — no dye or paint used

Tens of thousands of tests to get the color right
The underlying technique was first developed in the United Kingdom in 1972. It has been known for decades, but rarely used in practical products — because controlling the color with precision is extremely difficult. There is no textbook for this application. The process cannot be easily replicated.

Nakano Kagaku, a surface finishing specialist based in Tsubame, Niigata, has been working on surface treatment technology for over 60 years. Using this accumulated knowledge as a foundation, they developed their own proprietary oxide coloring process. The number of test records accumulated in the process of making IROAI's colors repeatable and precise runs into the tens of thousands.

Each color in the IROAI lineup appears only when the material selection, the polishing standard, and the oxide treatment conditions align exactly. The iridescent result is not a shortcut — it is the endpoint of considerable accumulated effort.