Ink Review: Sailor Souboku

Sailor Souboku writing sample

I’ve been using Souboku with a few pens, but to really test it, I used it for six weeks in two pens: a Nemosine Singularity with a medium stub nib, and a Kaweco Sport with fine nib.

Souboku is a wetter ink. When I paired it with a wet-writing pen and wrote on fountain-pen friendly paper, I found dry time to be a bit longer than average. To the point that if you forgot that, you might smudge the ink before it dried. Then your blue fingers would remind you the next time.

Startup was excellent. In fact, when I picked up the Kaweco Sport after not using it for over a week, the ink began flowing the moment I touched nib to paper. That was a nice surprise.

I’ll go to the writing samples next, to show the ink in action, but please note that both these pens are writing very wet (the Singularity because I primed the converter). In a dry-writing pen, Souboku would have look grayer.

Here is a writing sample on Rhodia.

Sailor Souboku writing sample

At the end of that writing sample, I flipped the Kaweco Sport nib, to show how the ink looks with a narrower nib. And the answer is: legible and crisp.

Here is Souboku on another fountain-pen friendly paper, the cream-colored Tomoe River.

Sailor Souboku writing sample

I liked Souboku on Tomoe River, and I see a tiny hint of sheen there, though I certainly wasn’t trying for it — that’s a medium stub. It has an interesting vibe that makes you wonder if you could get some sheen in a different pen.

Now here is a closeup of Souboku on my typical “normal paper,” Staples Sustainable Earth legal pad paper.

Sailor Souboku writing sample

That’s the downside: Souboku does have a tendency to feather a little on regular paper, especially from a wetter pen. It’s not terrible or disqualifying feathering, for me, but it is something I noted as I used Souboku on regular paper.

To bring out its best, Souboku benefits from more expensive, fountain-pen friendly papers like Rhodia or Tomoe River. The ink has nice shading and a crisper look on those papers.

It also benefits from a wetter-writing pen, which gives it a darker color. In a pen with dryer ink flow, Souboku dries grayer. It has a slightly green and slightly gray tint, which I like, but a wetter pen perks it up.

If you’re looking for a waterproof ink, Souboku is an excellent choice. Here are writing samples on normal, absorbent paper and on fountain-pen friendly Rhodia after exposure to running water.

Sailor Souboku water resistance

The writing holds completely on exposure to water, even on the coated Rhodia.

Best of all? Even though it’s a pigment ink, and waterproof, I found Souboku very easy to clean out of a pen. Even after six weeks, it cleaned quickly out of both the Kaweco Sport and Nemosine Singularity. That was designed as a pretty tough test, and Souboku passed with flying colors. I’ll have no fears using Souboku in a more expensive pen.

Souboku is also, in my opinion, reasonably priced. You can buy a box of 12 cartridges for $10 or a 50 ml bottle of ink for $24; I got my bottle from the Nibsmith.

That’s the same price as a 50 ml bottle of Sailor Seiboku, Sailor’s other blue pigment ink. (The older Seiboku used to be written Sei-boku, but Sailor now denominates it Seiboku, no hyphen, which mirrors Souboku. I’ll follow Sailor’s lead in this post.)

The newer Souboku does come in a nicer bottle, a rectangular prism that is a larger version of the 20 ml Shikiori bottles.

Sailor Souboku

Both Sailor blue-black pigment inks cost slightly more than Platinum’s offering, Platinum Blue-Black, which I’ve also been using, and which I’ll review next.

Here is a swab comparison of Platinum Blue-Black to Sailor’s new Souboku and then the older Sailor Seiboku.

Platinum Blue-Black Sailor Souboku ink comparisons

These are three very different renditions of the notion of a blue-black pigment ink.

If I’m comparing just the two Sailor inks, the newer Souboku is far and away my choice over the older Seiboku. That’s because the newer Souboku is low-maintenance, while the older Seiboku is high-maintenance. Sure the color of the older Seiboku is fun, but I just won’t keep an ink I worry about using in nicer pens.

Platinum Blue-Black is like Souboku in being very low-maintenance. Differences include, obviously, color, but also the level of resistance to water. Souboku is perfectly waterproof, while Platinum Blue-Black is only water-resistant.

Now here is Souboku compared to a few other grayish blue blacks.

Sailor Souboku ink comparisons

Though none of these are identical to Souboku, of course, an intriguing alternative is the dye-based Sailor Jentle Blue Black, which is a very good ink priced at only $12.50 for a 50 ml bottle. Sailor Jentle Blue Black has some water-resistance, too, though it’s not completely waterproof like Souboku. And it’s not a pigment ink.

I’m pretty happy with Souboku. It’s a waterproof pigment ink in a traditional blue black, that’s still easy on your pens. I like it better in a wetter pen, and better on fountain-pen friendly paper, but it’s a good ink.

10 thoughts on “Ink Review: Sailor Souboku

    1. Thank you. Rhodia is my favorite, but I actually use a lot of “normal” paper because I use my pens for work, and I usually write with fine and extra-fine nibs. I use Field Notes a lot, too — even the basic paper works for me with fine nib pens. 😊


  1. So did you prefer the Sailor or Platinum blue black carbon/nano pigment? The one I tried was Sei-boku, and I didn’t realize they changed the ink a little, and put it in a lovely bottle. Thank goodness it isn’t the small bottle either. I won’t go down that path today, but I could! I am interested in inks that are waterproof or at least water resistant, and recoverable. I also like to know how lightfast the inks are as well. I know Kiwa guro is totally waterproof, but the Sei-boku was not as waterproof as the black version. I may have to try this new version out in the future. I love the Platinum bottles, but I’ve never tried any of their ink. I have a Platinum pen and love it. I have just been more interested in Sailor ink/pens for some reason. The Pilot blue black did not enthuse me at all. I got a box of cartridges of it with my first Pilot Prera pen. That was used with an F nib, so maybe a heavier flowing nib would make me change my mind.

    Liked by 1 person

    1. Kelly, it’s super-confusing, and I can see I did not help. 😊 Thanks for giving me the chance to clear this up. I’m talking about three different blue-black pigment inks. Sailor Sei-boku (now called Sailor Seiboku without the hyphen) is one: it’s a pigment ink, also a blue black, but it’s a more bright color. This new ink I’m reviewing here is not a replacement for Seiboku, but an addition. It’s Sailor Souboku, also a pigment ink, also a blue black, but a grayer color. Platinum Blue-Black is the third: a blue black pigment ink that is more of a standard blue than either of the Sailor blue-black pigment inks.

      I’ve got one photo above comparing swabs of all three: the new Souboku with Platinum Blue-Black and Seiboku (which I at that point wrote as Sei-boku) — there you can see the differences. All three inks are still available.

      All three, plus the two black pigment inks Sailor Kiwa-guro and Platinum Carbon Black, are either very water-resistant or completely waterproof — to different degrees. I don’t remember the degree of water-resistance with Sailor Seiboku, but of the other four, the completely waterproof two are Platinum Carbon Black and Sailor Souboku (the new one). The water-resistant but not waterproof two are Sailor Kiwa-guro and Platinum Blue-Black. That’s been my experience at least.

      I have no idea about lightfast qualities.

      I do not like Sailor Seiboku (the older one), because it was very high-maintenance for me. I do like Sailor Souboku (the one reviewed here). I also like Platinum Blue-Black. My favorite is Platinum Blue-Black.

      I think Pilot Blue Black is a very fine ink, but you say it perfectly: it does not enthuse me, either. I know other people feel like that about the blue inks I like. It’s all good; something for everyone.

      At a certain point, though, I can’t help thinking that I also could have stopped at Waterman Serenity Blue or Aurora Blue, and Pelikan Brilliant Black or Montblanc Mystery Black, and been just fine. Except hundreds of dollars richer. 😆


      1. Oh, I am so glad that you cleared that up. It is confusing for sure. You went into great detail, and I do appreciate that. That is one reason I’m on hold for another blue black too. Now I MIGHT make an exception for the Sailor-Seiboku, just because of what you said about it. If it is truly waterproof and easier to deal with, I want to at least try that before long. One day I will try the Platinum inks. I wanted to try the Sepia nano, but heard it didn’t do well on a uv test.

        Liked by 1 person

        1. I have a visual memory so I remember them by their color. But maybe we should make a rhyme of it? How about, “Sou for you.” 😂 Or, Sou buy two. Woo for Sou. Stick to Sou. 🤩

          I do want to repeat that I like the color of Seiboku, and that I’m sure many people use it happily. I just found Seiboku high-maintenance, with some staining concerns, so I personally would only use it in a dedicated or cheap pen. Whereas Souboku (this new one) was very low-maintenance, so I will use it in my nicer pens. That’s why I prefer Souboku. I’ll stick to Sou. 😊 But Seiboku is a good ink, too.



    In all seriousness, good review, but I am very, very hard-pressed to consider yet another b/b ink. What I would be *really* curious to see you do is compare it to the non-pigment Pilot B/B (the 350ml “Coke bottle” ink for $22) and see how they fair (fare?) next to each other. I learned about that ink from Dan.

    I bet b/b, in some fashion, was the first ink I ever used, 50 years ago.

    Liked by 1 person

    1. (Prepare for a comment so long it reminds you of War and Peace.)

      I know PIlot Blue Black. I used to own Pilot Blue Black, but don’t any more. Someone in my family likes it, so I last used it in January. I find it perfectly decent, just as good as the more expensive Pilot-Iroshizuku Shin-kai, and very similar. It’s a gray-leaning blue black. I have no idea of its water-resistance — unless I’m doing a review, when it comes to water-resistance, I’m a classic Jay Cutler “Don’t care!”

      Souboku strikes me as more attractive and interesting than Pilot Blue-Black, without being able to compare the two at the same time. Souboku has a touch of green, almost, and if you use it on fountain-pen friendly paper, it’s got pizzazz and some three-dimensionality. It’s a pigment ink, so it’s got more going on.

      In contrast, I think of Pilot Blue Black more like Waterman Serenity Blue: not exciting, but if you like the color, a fine everyday ink. I prefer the color of Waterman Serenity Blue, and I love its behavior, so that’s my standard for an everyday ink. Others may choose Pilot Blue Black instead.

      Let me put it this way: I’ll never choose to use Pilot Blue Black again, because to me there’s nothing special about it. Life being short. But I will choose to use Souboku again. It’s more interesting. Every time I buy an ordinary gray-leaning blue black, I end up thinking, huh. So that’s all there is.

      Souboku is better than that.

      But still, I have to warn you about something. The next ink I’m going to review isn’t even blue black, but just blue. So if you think this was unexciting, I want you near a defibrillator before I hit “publish” on the next one. You may need a jolt to get back going….


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