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.
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.
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.
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.
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.
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.
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.
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.