Review: Sakura Koi Coloring Brush Pen (6-pc grey set)

I mostly use water-based markers to shade sketches and to add basic tones to comics, so I figured, instead of grabbing a bunch of single markers like I usually do, why not try this 6-piece set of greytone Sakura Koi “Coloring” Brush Pens?

Sakura Koi Coloring Brush Pen, front and back packaging
Sakura Koi Coloring Brush Pen, front and back packaging.

These are disposable, felt-tip brush pens with water-based, dyestuff ink. The pen bodies all say “coloring brush pen,” but the front packaging calls them “watercolor brush pens.” It’s unclear to me whether these are specifically intended for use with water or watercolors, but Koi is also the name of Sakura’s line of actual watercolors, available in both tubes and pans, so… maybe?

Available in 48 colors, the Sakura Koi brush pens are single-tipped and pen-sized, not marker-sized. The pen caps correspond to the color, but annoyingly, neither color name nor code appear anywhere except in tiny text above the bar code on a graphically busy pen body. This seems like a stupid oversight since we all know that cap colors never really correspond to actual colors.

This is particularly true for greys, where it’s important to match both value (relative dark/lightness) and hue (“color”).

Sakura Koi Coloring Brush Pen, grey set
Sakura Koi Coloring Brush Pen, 6-piece grey set, on Strathmore Bristol. The numbering for these colors makes no sense to me. Why tf is Warm Grey numerically between Dark Cool Grey and Cool Grey??

The 6-piece grey set comes with three cool greys and three warm greys, with light, regular, and dark variations of each. It is not obvious which are cool and which are warm from the caps, and the color values are also really hard to tell at a glance. I ended up writing the color names on the caps in Sharpie.

The greys within their temperature group are really inconsistent.

Dark Cool Grey is significantly bluer/greener than Cool Grey, which is more neutral, and Light Cool Grey, which is way more neutral. Light and Dark Warm Grey, meanwhile, are both more neutral than Warm Grey, which is super reddish. It seems to me like Cool Grey, Light Cool Grey, Light Warm Grey, and Dark Warm Grey are fairly close in temperature (and neutralish), while Dark Cool Grey and Warm Grey are weird outliers.

Sakura Koi Coloring Brush Pen
Mixing colors within the temperature groups, on Bristol. Left is the Cool Greys; right is the Warm Greys. Top is mixing while wet. Bottom is mixing after the first color has dried.

The brush tip is ~9 mm long and ~4.5 mm at the base, but only about the last 4 mm of the tip is flexible. The felt in the tip isn’t very dense; you can see all the fibrous bits pretty clearly, which makes it obvious it’s not a very durable brush. It’s gonna deform and fray pretty fast.

Fine strokes are hard to get and even harder to control, and it’s hard to taper strokes. It’s serviceable enough for sketching, but definitely not for inking.

A dove drawing with Sakura Koi Coloring Brush
A dove drawing with Sakura Koi Coloring Brush in a Punctuate Sketchbook. Would have preferred to be able to get more taper in the lines around the neck and the base of the legs.

The poor temperature matching for the greys is obvious any time you use the colors together.

This isn’t a huge deal for sketches, nor if you’re using the actual color markers. It annoyed me a bit, but the mismatchedness of it sort of grew on me over time, maybe because it felt like a weird limited palette exercise?

Dove with Sakura Koi Coloring Brush Pen Cool Greys
Dove with Sakura Koi Coloring Brush Pen Cool Greys. It’s super obvious the Dark Cool Grey is a totally different hue than the other two.

The ink in the Sakura Koi brush pen comes out really wet. It dries pretty quickly on cheaper, more absorbent papers, like printer paper or index cards, but on Bristol it takes about 6-8 seconds before you can touch it without smearing. This is also true for watercolor paper.

It’s only on those thicker papers that you can manipulate the ink with water after it’s dried though. The thinner papers don’t hold up against water in the first place, but on watercolor paper, you can add water and then push the dye-ink around and spread it.

Sakura Koi Coloring Brush with water
Inked with Sakura Pigma Brush & Pigma Sensei on Strathmore cold press paper (140 lb/300 gsm). Shaded with Sakura Koi brush pen. Then I added some water (with a Niji Waterbrush).

The final result can look pretty close to actual watercolors. The benefit of the brush pen is just that it’s way faster, more consistent, and more precise to start with. You can go directly from the first to last step above with real watercolor, but it’d take longer and the grey wouldn’t be as even. That variation is some of the charm of watercolor, but it can slow you down if you’re just wanting to throw down some simple value.

With a brush pen, you can get into the fine areas of pigeon neck fluff and wing feathers more easily and then soften edges as desired with water afterwards. And once it’s dry, you can go back in with the brush pen again if some of the details got washed out — that’s probably the best part, since the colors you used will match exactly. Here’s the final pigeon:

Sakura Koi Coloring Brush with water
What a fancy pigeon.

Wet-on-wet techniques don’t work as well with the Sakura Koi brush pen. As with the Akashiya Sai watercolor brush pen and the Winsor & Newton watercolor marker, color washes out of the tip very quickly when it makes contact with water, so you have to keep waiting for new ink to drain into the brush tip before depositing more of it onto the page.

You can forget about trying to put down fine lines on a wet page, but using the side of the brush to get broad strokes works okay, especially for darker colors. The ink is pretty easily manipulated on the page when wet, which is what makes it most similar to watercolor.

Overall, I think the Sakura Koi brush pen is more fun to use as a watercolor-mimicking tool. Some of the weaknesses of the brush tip become moot when you plan to soften everything with water later anyway, and the brush is still good enough for minor detailing on top of a “painting” once dry.

Some mountains with the Sakura Koi Coloring Brush Pen using wet-on-wet techniques
Some mountains with the Sakura Koi Coloring Brush Pen using wet-on-wet techniques.

For drawing and sketching, the Sakura Koi brush pens are just okay. Its weaknesses aren’t uncommon for the category. The 6-piece grey set is $14.94 MSRP, which comes out to $2.49/marker, which is what Blick has for the price of open stock. Few other retailers have open stock available, though the sets are often available for cheaper than MSRP, including at Blick. I got mine for $11.50 a while back, so just under $2/marker.

All of these prices are within a fairly typical range for (single) water-based brush pens, though many alternatives are dual-tip. Sakura Koi might be intended to be used in a watercolor-like way, but the truth is you can achieve similar effects with most water-based markers, whether or not they’re specifically marketed as “watercolor markers.” They’re all water-soluble, after all.

I don’t really feel strongly about the Sakura Koi brush pens one way or another. They’re fine. The price is fine. It’s fun to add water and push ink around. They’re okay for dry use, too. Most other felt-tip water-based pens also fall squarely in the category of “fine,” so it’s anyone’s pick. (This does make Akashiya Sai the fun outlier though — it has a bristle brush tip!)

Portrait with Sakura Koi Coloring Brush Pen in warm greys
A portrait using the warm greys in the set. This was “inked” initially with Dark Warm Grey, then water was added, then some regular Warm Grey, then more water, then final details.

About the author

Kiri is a Seattle-based artist, writer, webmaster, and (brush) pen enthusiast with over 12 years of convention and event vending experience and a lot of opinions.