Compiled from 7 sources; we haven't tested this product ourselves yet. How we research
Quick answer
Sailor Kiwa-guro is a black pigment fountain pen ink from Sailor of Japan, sold in a 50 ml (1.7 fl oz) glass bottle 70 mm (2.8 in) tall. Sailor says its ultra-fine pigment resists water, feathering and bleed-through. It's dry to the touch in about 40 seconds but can smear until 100, and pens need regular cleaning.
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The 50 ml bottle to scale (1 mm = 2.8 px), from Sailor Japan's dimensions.
Product facts
Product
Sailor Kiwa-guro pigment fountain pen ink, 50 ml bottle
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Notes on these facts
Made by The Sailor Pen Co., Ltd., Kure, Hiroshima, Japan; majority-owned by PLUS Corporation since May 2022. Made in Japan: Hiroshima Prefecture's profile of Sailor says its site in Kure, Hiroshima makes fountain pens, inks and ballpoints, and the bottle's JAN 4901680184508 carries Japan's 49 GS1 prefix (it shows where the code was registered). Sailor's product page (read in full on October 21, 2026) doesn't print a country of origin. Source. Price: example listing.
Price bands are typical US retail, checked October 2026. Conversions to US dollars are approximate, at October 2026 rates (US$1 = ¥158 = ₩1,330 = NT$32.5 = CN¥6.7 = SEK 9.9 = DKK 6.7 = ₺49.6 = C$1.41 = A$1.43 = CZK 21.7; €1 = US$1.12; £1 = US$1.32; CHF 1 = US$1.21).
Key takeaways
Sailor's Japanese site lists the 50 ml bottle (13-2002-220) at W53 × D44 × H70 mm (2.1 × 1.7 × 2.8 in) and about 203 g.
It lists at ¥2,530 (about US$16) including tax in Japan.
Mountain of Ink rates its water resistance high: the ink did not budge.
Mountain of Ink found it dry at 40 seconds but able to smear until 100 seconds.
On October 21, 2026 it was the 46th best-selling bottled ink on Amazon US, the second pigment black after Platinum Carbon Black.
What is Sailor Kiwa-guro?
It’s a black pigment fountain pen ink from Sailor of Japan, made with what Sailor calls an ultra-fine pigment it developed itself. Kiwa-guro (極黒) means extreme black, and US shops sell it as Kiwaguro Pigmented Black or Nano Black.
Sailor’s Japanese page says the ink resists clogging and writes as comfortably as a dye ink, while resisting water, feathering and bleed-through, so it suits anything from illustration to official documents. Wonder Pens notes it’s one of Sailor’s two original pigment inks, with the blue-black Sei-boku. Sailor has made pens in Kure, Hiroshima since 1911, as our Sailor history explains.
On October 21, 2026 it was the 46th best-selling bottled ink on Amazon US; the only pigment fountain pen ink above it was Platinum Carbon Black, at 5th.
Kiwa-guro specs
Spec
Value
Maker
The Sailor Pen Co., Ltd., Japan
Code
13-2002-220, JAN 4901680184508
Bottle
50 ml (1.7 fl oz), glass
Bottle size and weight
W53 × D44 × H70 mm (2.1 × 1.7 × 2.8 in), about 203 g (Sailor Japan)
Bottle opening
20.6 mm (0.81 in), per Goulet
Ink type
Ultra-fine pigment (Sailor Japan)
Water resistance
High (Mountain of Ink)
Dry time
Dry at 40 s; shine smears until 100 s (Mountain of Ink)
Japan list price
¥2,530 (about US$16) incl. tax; ¥2,300 (about US$15) before tax
Price band
$$$ ($20–75 per bottle)
Sailor’s page notes that the bottle no longer comes with an ink reservoir insert. Goulet also sells Kiwa-guro as Sailor cartridges.
How many converter fills one 50 ml bottle holds (bottle ÷ capacity), with Kiwa-guro's sourced properties.
How water resistant is Kiwa-guro?
Very: in Mountain of Ink’s test, the writing didn’t budge. Sailor’s Japanese page lists water resistance first among the pigment ink’s strengths, and Goulet marks it as water resistant.
That makes it a pick for envelopes, signatures and line work under watercolor. A Goulet customer who paints over it in a 180 gsm sketchbook waits a few hours first for the best result.
How does it look and how fast does it dry?
A dense, shiny black that’s dry to the touch in about 40 seconds but smearable until about 100. Mountain of Ink calls it very shiny rather than sheening, with no shading.
Wonder Pens describes it as matte head-on with a hint of shine at an angle. On copy paper Mountain of Ink saw just a little feathering and no bleeding.
Which pens is Kiwa-guro safe for?
Pens you write with often and can flush easily, ideally a Sailor. Sailor’s Japanese page says to use it in Sailor fountain pens and that it can’t guarantee pens from other makers.
A Sailor Pro Gear Slim is the natural match. Wonder Pens says you shouldn’t have clogging problems with good habits: write every other day or so, don’t let the pen dry out, and flush between fills.
How do you clean it out?
Flush with water before the ink can dry in the feed, and clean the pen between fills. Pigment particles stay put once dry, which is what makes the ink water resistant and also what makes a neglected pen hard to clear.
If a pen has sat inked for weeks, soak the nib and feed in water before flushing. Don’t use it in a pen you might forget in a drawer.
How does Kiwa-guro compare with other black inks?
It’s the most water resistant of the easy-flowing blacks, at the cost of more care.
In Japan. Hiroshima Prefecture’s profile of Sailor says the company’s site in Kure, Hiroshima makes its fountain pens and inks, and the bottle’s JAN code is Japanese. Sailor’s product page doesn’t print a country.
Sailor has been majority-owned by PLUS Corporation since May 2022. We didn’t find a Sailor date for Kiwa-guro’s launch.
Frequently asked questions
What does Kiwa-guro mean?
Extreme black (極黒). Sailor's Japanese site names the ink 極黒（きわぐろ）, and US retailers sell it as Kiwaguro Pigmented Black or Nano Black.
Is Sailor Kiwa-guro waterproof?
It's highly water resistant. Sailor says the pigment ink is strong against water, Goulet lists it as water resistant, and in Mountain of Ink's test the writing didn't budge.
Can I use Kiwa-guro in a non-Sailor pen?
Many people do, but Sailor's Japanese page tells you to use it in Sailor fountain pens and says it can't guarantee other makers' pens. Keep it in a pen you write with often and can flush easily.
Will pigment ink clog my fountain pen?
Not if you use the pen regularly. Wonder Pens advises writing with it every other day or so, never letting it dry out, and flushing the pen between fills rather than topping it up.
Why does Kiwa-guro smear after it looks dry?
Its shiny finish stays soft. Mountain of Ink found it dry at 40 seconds but still smearable until 100, so give it time on coated paper or blot it.
Is Kiwa-guro good for drawing with watercolor?
Yes, it's a sketcher favorite. Goulet says artists like it for its water resistance, and one Goulet customer uses it under watercolor and gouache after letting it cure for a few hours.
Is Sailor ink made in Japan?
Yes. Hiroshima Prefecture's profile of Sailor says its Kure site makes the company's inks, and the bottle carries a Japanese JAN code.
