Bluish inksticks ( Seiboku, 青墨 ）

There's a reason seiboku looks blue rather than warm black: the same optical principle that colors the sky.

Very fine soot particles scatter light unevenly, favoring blue wavelengths over red — the finer the particle, the cooler the tone.

That blue-black is admired well beyond calligraphy studios: Sailor, Japan's celebrated pen maker, named a nano-pigment fountain pen ink after it, prized worldwide by enthusiasts for its teal-leaning shading.

Kobaien's Seiboku inksticks carry that same character in its original form — ground fresh from soot and glue, centuries before ink ever came in a bottle.

The following list is arranged in order of product popularity.