What Is Sheen in Ink

You might see this SHEEN in many articles talking about fountain pen ink, junk journal or other related content. Then what is SHEEN referred to?  And how do we get this sheen thing?
Sheen is the metallic luster or rainbow-colored reflection phenomenon of fountain pen ink under certain conditions, which usually appears at the edge of the handwriting or accumulation after the ink dries. This effect is not the color of the ink itself, but an optical phenomenon caused by the refraction or interference of light on the surface of the ink components, similar to the color reflection of oil film on the water surface.

1. The formation principle of Sheen

Ink ingredients:

Contains high concentrations of dyes or special chemicals (such as polyvinyl pyrrolidone, PVP), which form microcrystalline or film structures after drying.

Commonly seen in highly saturated inks (such as Organic Studio Nitrogen, Sailor Four Seasons Color Series).

Notebook Paper:

Smooth notebook paper (such as coated paper, tomoe river paper) is more likely to show sheen, because the ink is not easy to penetrate and will accumulate on the surface.

Paper with strong ink absorption (such as newsprint) hardly shows sheen.

Writing method:

The thicker the ink accumulation (such as slow writing, painting), the more obvious the sheen.

2. Typical performance of Sheen

Color type Representative ink Effect example
Red series Organic Studio Nitrogen (blue → red copper flash) Dark blue base + red copper reflection
Gold series Sailor Shikicai Yamadori (purple → gold flash) Purple base + gold luster
Green series Diami Eau de Nil (blue-green → pink glitter) Blue-green base + pink reflection

3. Difference between Sheen and Shading (gradient)
Characteristics Sheen Shading
Visual effect Metallic luster/rainbow reflection Gradual change of light and dark of the same color
Cause of formation Optical effect of ink surface Uneven distribution of ink on paper surface
Typical ink High saturation dye ink Low viscosity water-based ink (such as Pilot Color Shizuku)

4. How to enhance the Sheen effect

Choose the right ink:

High sheen ink: Organic Studio, Diami, Sailor Storia series.

Matched paper:
Recommended: Tomoe river paper (52g), Rhodia Premium, Maruman Mnemosyne.

Writing skills:

Write slowly and let the ink accumulate.
Use a broad-tipped fountain pen (such as a B-tip) or a dip pen.

V. Advantages and disadvantages of Sheen ink
Advantages:

Stunning visual effects, suitable for artistic creation and special writing.
The same bottle of ink can present two colors (base color + reflective color).

Disadvantages:

Slow drying, easy to rub (need to wait 20-30 seconds).
After long-term storage, sheen may weaken (shaking the ink can restore it).

VI. Cleaning and maintenance

Anti-clogging: High sheen ink is easy to remain, and the pen needs to be cleaned regularly (once a month).
Storage: Keep away from light to prevent dye decomposition.