Fountain pen inks with the Pentel pocket brush

Most brush pens only come in black. Occasionally, they also come in grey, but very rarely are there any additional colors.

My favourite brush pen, the Pentel pocket brush, only has black cartridge inks available. A few years ago, when I picked up a new Pentel pocket brush for a fresh tip, I decided to syringe-fill the old one with grey ink (specifically J. Herbin’s Gris Nuage). This was a great decision, and I’ve really enjoyed being able to use my fav pen to add value to drawings in addition to making the lines.

More recently, Pentel decided to release five limited edition versions of the pocket brush with different colored pen bodies. Alas, they’ve found my weakness… collectibles and colors.

The limited edition (LE) camellia Pentel pocket brush
The limited edition (LE) camellia Pentel pocket brush

I picked up the green (bamboo) one first, because green is the best color, and ostensibly because it was about time for a fresh pen anyway and I was also pretty tired of losing my solid black pen on my solid black table and in my black bags and on my black clothes (lol). And the new pen’s great! It’s just a normal Pentel pocket brush with a fresh, colorful body. It handles just like all the other ones I’ve had.

But inevitably, I started eyeing the purple (wisteria) and red (camellia) ones too. They’re both so pretty!

The LE pens all still have the standard black refills, but since I 1) probably don’t need multiple identical pens with the same ink, and 2) have enjoyed my old Pentel with grey ink, the perfect justification for getting more of the LE pens was so I could fill them with additional colors of ink.

Red is a great accent color in general, and doubly good for someone who draws a lot of horror. And look, if I’m gonna have the green and red pen, I might as well get the purple one too! (The marble and mahogany ones are not in my collection yet, but let’s be real, it’s probably just a matter of time.)

All the Pentel pocket brushes currently in my possession
All the Pentel pocket brushes currently in my possession… I’ve had an unopened regular edition pen (far left) for a while. In case of emergency.

I explained syringe-filling in depth when I was trying to figure out how to refill my Daiso fountain pen. It’s a little intimidating at first, but you get the hang of it fast, and thereafter you have the freedom to fill your cartridge pens with whatever you want. That freedom is, of course, both a blessing and a curse, as the world of fountain pen inks is very vast. Indeed, inks are absolutely terrifying to someone who likes 1) collecting things and 2) pretty colors, and I’ve avoided it a long time for that reason.

While you can find sampler bottles at 5 mL or 10 mL for some, most fountain pen inks come in bottles at least 30 mL in size, which means they’ll last a very long time. My 30 mL bottle of J. Herbin’s Gris Nuage still has about… a sixth left? after more than three years of regular refills. This, at least, has been a good reason to keep my ink collection under control. I don’t have a lot of room to store things, so I need to be using the inks I buy.

The LE camellia Pentel pocket brush, a bottle of Robert Oster's Astorquiza Rot red ink, and a blunt-tip syringe.
The LE camellia Pentel pocket brush, a bottle of Robert Oster’s Astorquiza Rot red ink, and a blunt-tip syringe.

“But what about the Pentel Art Brush? Those already come in a bunch of colors, so you don’t have to syringe-fill anything or buy separate inks…”

You’re right, and I don’t have any particular reason to not use Pentel art brushes except that I don’t remember really enjoying those pens the last time I used one (a very long time ago) — the squeezy body made ink flow kind of inconsistent. The brush tip is also larger than the one on the pocket brush, pushing it over into the unwieldy territory, in my opinion. At least for drawing and sketching — it’s probably still fine for lettering.

Besides, one bottle of ink is how many cartridge refills? It’s not hard to guess that buying a bottle of ink is way more cost efficient than dealing with a dozen tiny refills, but here’s the math for funsies:

At $2.45 a pop, a mere three (3) refills already costs the same as a 30 mL bottle of standard Diamine ink ($7.50). Even your pricier bottles of (30 mL) ink top out around $20, which is the cost of eight (8) cartridge refills.

Most pen cartridges have between 1.3-1.7 mL of capacity. Since the art brush’s whole body is a reservoir, I’m gonna guess very high and say it can hold 3-3.5 mL, but even then, eight refills (8 x 3.5 mL = 28 mL) isn’t as good as 30 mL of ink. With larger bottles of ink, the savings are even bigger.

Besides, the refills for the Pentel art brush being the entire pen body just makes it extra obvious it’s only there to keep the refills proprietary. Technically, with the squeeze mechanism of the art brush, you could just suction ink out of a bottle and into the pen body/reservoir, but that sounds way messier than syringe-filling a normal cartridge.

Wtriting sample and pen test with Pentel pocket brush and three different inks.
Pentel pocket brush and three different inks.

One of the things I really like about using fountain pen inks is that they often have some degree of “shading,” or the tendency for ink to pool unevenly within a stroke, leading to areas of deeper saturation and a nice overall variation in color. You can see some in the above example when I press down and make blobs in the middle of a stroke. For the red, this makes it look a little more like fresh blood. ;)

Shading can be inconvenient if you’re aiming for consistency, but if you prefer solid color blocks to add value to sketches, you’re probably better off using markers. (And I do often use markers!) But I think ink shading adds (or emphasizes) a dynamic, organic feeling in sketches, which can be really fun sometimes.

Sketch with three Pentel pocket brushes!
Sketch with three Pentel pocket brushes!

Remember to only fill brush pens (and fountain pens) with fountain pen ink though.

The pen bodies and cartridge reservoirs aren’t air tight, so typical, pigment-based artist inks for use with brushes and dip pens will dry up fast, leading to clogging and dried up bristles. Since the Pentel pocket brush’s bristles are synthetic nylon, they probably won’t sustain too much lasting damage once you wash out the dried ink, but I still wouldn’t recommend it.

I’ve tried before to fill my pocket brush with very small amounts of inks like Deleter Black and Dr. Ph. Martin’s Bombay India Ink. It works okay for a while, but inevitably starts to skip and clog. Better to stick with dipping the brush into the ink bottle for those types of inks, though there’s nothing wrong with dipping a Pentel pocket brush instead of a “real” brush!

My current ink collection
My current ink collection. The five on the left are pigment-based and I wouldn’t put into my brush pens; the three on the right are dye-based and I would!

Because they’re typically dye-based, most fountain pen inks are not waterproof. But as long as you’re aware of that, it can be fun to play around with.

While they can look deceptively like watercolor (which, like artist inks, are usually pigment-based), being dye-based gives fountain pen inks a wider and often more vibrant range of color. They’re also not as opaque, since there’s no physical component (pigment) to layer onto the page. This is also why they won’t clog your brush — there’s no pigment to clog with. The ink is entirely liquid.

This also means they aren’t as forgiving as watercolor, which you can still push around on the page after the fact, or blot out entirely, as long as the page is (re)wet enough to move pigment around. There’s no pushing around ink once it’s dried on the page, but that’s what makes it great for quick sketch work, too.

Most inks will say whether they’re pigment-based or dye-based on the label, but if not, it’s usually the case that inks marketed towards artists are pigment-based, while inks marketed towards fountain pen users are dye-based.

Sketch with Pentel pocket brush and three different inks
Happy inking!

My green Pentel pocket brush currently has the default black ink, but I’m gonna swap in the Waterman Harmonious Green ink I’ve been using in my fountain pens and use the purple one as my default black ink one while I figure out what kind of purple ink I want… This is why it’s inevitable that I end up with the marble and mahogany versions as well… I need one of them to be my default black ink pen! And it’s just silly to have 4 of 5 of a set.

So yeah, ink up your extra cartridge-fill brush pens with different colors! It’s fun and a great excuse to buy more pens, because you totally need more pens!

Too many Pentel pocket brushes...

About the author

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