Sailor is one of the three Japanese giants of fountain pen industry. The other two are Platinum and Pilot. While they all make excellent pens, or so I hear, they also make an amazing ink. Sailor in particular makes wonderful limited editions and I believe is the largest ink producer in Japan, supplying shops around Japan with variety of custom, specialty inks. For the rest of the world they periodically release special editions of their “Jentle” line. Jentle inks are definitely one of the most loved inks by the community. And rightly so. The properties are almost always exceptional and the inks are a joy to use.

Today’s ink, however, is not one of their standard, nor special edition Jentle line. It belongs to the “Nano” line, which is Sailor’s pigment based ink line. There are currently only two Nano Sailor inks, Black and Blue Black. In this article we’ll take a look at the Sei-Boku Blue Black ink.

A list of properties and my experience with using the ink extensively can be found at the end of this post.

Ink Card

Sailor Nano Blue Black fountain pen ink
Sailor Nano Blue Black fountain pen ink
Sailor Nano Blue Black fountain pen ink
Sailor Nano Blue Black fountain pen ink

The ink cards I use are made by “maruman” and are actually called Word Cards. They use watercolor paper but unfortunately they don’t specify the content of cotton nor the weight of the paper. Nor they state whether the paper is acid free or not. It is, however, good for visual demonstration of the characteristics of the ink. Unfortunately, I believe the Word Cards are no longer made but there are other methods of making these samples, and so I don’t see it as a tremendous loss. Cutting one’s own cards from the best quality watercolor paper may be far better option, even if not as convenient.

As for the ink itself, Sei-Boku is a cool hue of blue. It is a good middle value ink that shades, which means that the value shifts from middle to dark middle, even to dark. It does even produce red sheen on right paper. However, I find it needs to be applied fairly heavily for the sheen to show consistently.

The ink is fairly dry and quick drying. It feels as if it leaves a film behind, unlike other inks, which have a more watery consistency and feel. I believe this is in part due to the pigment component in the ink.

As I mentioned, Sei-Boku belongs to the Sailor’s “Nano” line. Unlike the majority of fountain pen inks, the Nano inks are pigment, rather than dye, based. The reason why fountain pen inks are in majority dye based is the fountain pen feed mechanism, or the ink regulator. The feed can get clogged when not attended regularly, even with a relatively watery dye based ink. This is due to evaporation. When the water evaporates from the ink that’s in the feed, it leaves behind the dye component, which blocks the ink channel. In the case of pigmented inks the risk of clogging and damaging the ink regulator increases dramatically because even if the ink doesn’t dry out, the pigment particles settle down and can cause problems.

Bottle Design and Functionality

Sailor Nano Blue Black fountain pen ink
Sailor Nano Blue Black fountain pen ink

The ink comes in Sailor regular ink bottle which contains 50 ml of ink, only difference is the sticker on the side of the bottle. The Japanese characters on it look extremely cool. The box is beautifully designed as well, very exotic at least for a westerner. While Sei-Boku is not one of the most expensive inks, it’s pretty pricey. A bottle of 50 ml is sold for €22.

As for the esthetics of the bottle, I think it looks really nice. The design is definitely Japanese and minimalist. However, when we consider its functionality, it fails miserably. Just like the J. Herbin bottle I discussed in the Cacao du Brésil review, it simply won’t allow you to fill the pen, because it’s too short. At least it has a wide mouth, so when the bottle is full you can tilt it and fill a pen with larger nib.

Using the Ink

Sailor Nano Blue Black fountain pen ink in my sketchbook
Sailor Nano Blue Black fountain pen ink in my sketchbook

I used the ink extensively for some time now, both in my sketchbook and for writing. Subjectively, I’m not a great fan of this ink. While I enjoy the color and the permanent aspect, the ink doesn’t perform to my liking. This is partly a matter of personal preference, of course, so you may find that the ink is a great match for you. If you like dry inks that are permanent and prefer cool hues of blue, the ink may be just what you’re looking for. I personally much prefer warm blues with free flow.

I would like to share a word of caution with you about using this ink in any pen that is precious to you, or a pen made from a material that cannot be easily washed with bleach or a pen flush, such as Ebonite. While using the ink in my Ranga Bamboo, some ink leaked into the cap of my pen and ever since the pen was heavily stained, the threads dark blue and the section shiny red (the ink leaves a heavy red sheen). I managed to partially rid the pen of the stains in the course of past several months but it won’t ever be like new. Partly this was my fault as I should have reserved it for my cc or piston fillers where leakage doesn’t occur, but the fact remains that the ink is very aggressive in this respect and should be used with caution. Now don’t get me wrong, this ink is beautiful. Too dry for my liking, but the color, shading and sheen are amazing. On the page, the ink looks spectacular. I love everything about how it looks but there is the undeniable fact that once the ink sinks its teeth into something, it won’t let go. I even had problems to clean it from a stainless steel nib!

You can see more writing samples with the ink in my review of Ranga Bamboo fountain pen. Note that those images are not color corrected, however, while the images in this review are.

List of Properties and Behavior

Following are listed my subjective findings and conclusions observed during the time I used the ink.

Concentration and Chroma

The concentration parameter describes what is usually referred to in fountain pen community as “saturation”. However, the correct term describing the ratio of pigment/dye to vehicle is called pigment load, or concentration. The pureness, or “brightness” of a color is called chroma.

Based on the high pigment load, I think it could very well be suitable for dilution. I have not tried diluting it myself but I’m almost certain that diluting it with some distilled water not only improve the flow properties but also provides you with more value. When diluting any ink, please remember to isolate small quantities of the ink in a separate container first, so in case you don’t like the results your whole bottle won’t be ruined.

The blue hue is fairly low in chroma. It is not the brightest blue out there. It is, after all a blue black.

Hue and Value

The ink is a cool hue of blue. It is green-blue in color. The value is middle, in the places where it builds-up (shading), the ink goes up to dark-middle value to dark value. It is not very transparent.

Overall Flow Properties and Behavior

The ink flows well but I find it to be very dry. The lubrication seems to be all right but it is an ink that I would not put into a dry writing pen. The ink does not penetrates the paper fibers aggressively, it feels like it leaves a film on top of the page. Therefore it doesn’t bleed through or feather and I found it very easy to use on any paper.

Water Resistance and Permanence

The ink is waterproof.

Drying Times and Dry Smear

The ink dries very quickly. However, when I used it in a wet pen, I noticed a fair bit of dry smear. This is mainly a problem when you either use a non-absorbent paper or/and a wetter pen.

Special Properties

The ink has tendency to sheen. The sheen color is cool red-violet. This produces a really nice effect.

It also shades very well, from middle-value to dark-middle value, to dark in some places.


Due to the waterproof composition and the pigment particles, the ink sticks to steel nibs, ebonite and plastic feeds and majority of pen materials. It is very difficult to clean. Therefore it should be used with caution and proper pen hygiene should be maintained.

Some Comparable Inks

Sailor Nano Blue Black fountain pen ink compared to some similar inks
Sailor Nano Blue Black fountain pen ink compared to some similar inks

There are some comparable inks out there among which I can list the following:

  • Noodler’s Ink Bad Blue Heron: A dye based permanent ink from Noodler’s Ink. Bad Blue Heron belongs to the Warden/Eternal series, which is a series of extremely permanent inks. If you’re looking for an alternative to Sei-Boku, I would definitely recommend it. It’s an exceptional value. The ink is more feather/bleed prone than Sei-Boku but definitely worth checking out.
  • Diamine Denim: Not a permanent ink nor water resistant but one that is in the blue black color family. And a good performer.
  • KWZ Ink Iron-Gall Blue Black: An iron-gall based permanent ink from the Polish ink workshop KWZI. Very good alternative to Sei-Boku, note though that this ink is iron-gall which too requires a good pen hygiene and can be damaging to steel nibs when maintenance is neglected.
  • Pelikan 4001 Blue Black: Another ink based on iron-gall formula. Pelikan 4001 is a warmer hue of blue than Sei-Boku. It provides good writing experience as well as water resistance.
  • Rohrer & Klinger Iron-Gall Salix: Final ink in this comparison, the R&K Salix is another permanent iron-gall based ink. It is lighter than Pelikan 4001 and I find it more boring and drier. Still a good option for permanent writing though. Maintenance concerns apply.


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