Friday, December 02, 2016

Hacking the Pentel Pocketbrush

The Pentel Pocketbrush.  Sleek, lightweight plastic body.  Nylon bristles.  Plastic cap with metal clip.  Cartridge fed.  If it's not the Pentel Pocketbrush, it's probably the Pentel Kirari, the slightly overpriced sister who comes in metallic colors like Sakura Pink. This brushpen is ubiquitous amongst comic artists.  Go ahead, look in your pencil case, I'll wait.  If it's not there, it's hiding in your keyboard shelf, on the floor behind your computer, tucked into a backpack.  Most sketchers have one, and they're sold almost everywhere- from certain Walmarts to Michaels, to DickBlick and Jerry's Artarama. 

There's a lot to like about these brushpens, but as popular as they are, we have to admit there's a serious drawback:  Those little cartridges hold so little ink.

A few years ago, I shared a tutorial on how to refill your empties with the ink of your choice.  This takes patience, a syringe, and you're still limited with how much ink you can carry in your pen at any given time. 

A slip up on Amazon priced Pentel Pocketbrushes at $2.01 for half a day, and of course, being the person who first that slip, I bought 5.  That puts me in the comfortable position of being able to experiment, being able to make an already great, affordably priced, commonplace brushpen even better by increasing it's ink capacity.

So today, I answer two questions:  Can a Pentel PocketBrush be used with an eyedropper conversion or a cartridge to hold the ink of my choice? 



Easily Refillable
Could be refilled with ink of choice\
Could travel with less chance of leaking than an eyedropper conversion

So many converters on the market, to find the Cinderlla's slipper might cost a lot of money
Would hold about as much ink as the cartridges

My fountain pen readers know that there are loads of converters on the market, all made to suit the wide variety of fountain pens.  Literally every major FP brand makes their own, there's some deviation between makes.

Fairly standard piston fill converter. Image Source

While thinking about the possibility, I Skyped Heidi to see if she knew of any options.  As a Jetpens employee, she has access to a library of their products, and she said she'd try a few out, but that I should email her so she could get paid for her efforts (if only that worked for me too, haha).

So I sent this letter off to my buddy:

Hi Heidi,

As a longtime artist and illustrator, I am a huge fan of the Pentel Pocketbrush.  It's portable, compact, and easy to use- the only downfall are those tiny cartridges.  I've refilled them with the ink of my choice in the past, but I'd love to know if there are any converters on the market that are compatible with the Pocketbrush, and given your large catalogue of fountain pens and fountain pen accessories, I figured you guys might be able to give me the answer.  I run an art supply review/tutorial blog (, and I know my readers would love to know this information, and I'd be delighted to share it with them, as well  as the source.  So any recommendations on converters would be a huge help!

Becca Hillburn

And Heidi replied:

Hi Becca Hillburn,

Thank you for your email!

Alas, I just went through all of our converters and none of them fit on the Pentel Pocket Brush. I'm sorry I could not be of more help!

I own the Kuretake 13 brush pen, which is compatible with the Platinum fountain pen converter:

Please let us know if you have any further questions or concerns. Have a great day!

Best Regards,

So the answer for now is NO, there are no converters currently available that are compatible with the Pentel Pocket Brush. 

If you are looking for a refillable, non cartridge brush pen, Noodler's makes one with the Ahab body.   Looking at how the Noodler's brush fits into an Ahab body, and knowing that there are replacement brushes available, I'm curious about whether or not you could just put the brush tip into your existing Ahab once you've removed the feed and nib. This is an experiment I'd love to try once I own an Ahab of my own.  Please note that the 'brush' does not come to a point, so this functions more as a marker, and is probably intended for those fluorescents Noodler's makes.  Kuretake's No 13 brushpen apparently can take a Platinum fountain pen converter, and Platinum makes two brushpens (a fiber tip and a hair tip) that feature cartridges and are probably compatible with the Platinum converter.

This said, I'm a stubborn woman, and will probably try to fit converters as I purchase them for my fountain pens, just in case one went remiss.

Eye Dropper Conversion

Rubber gasket (I actually used an unused orthodontic rubberband)
Ink of choice (not acrylic or shellac based)

Could hold A LOT of ink
Could hold ink of choice if cleaned
If you find the Pentel Ink to be too gray, could use a heavier/more opaque ink ink
Can select ink based on properties you find useful- waterproof v waterbased, color, shading, ect.

Most likely to leak in transit
Not idea for everyday carry
Can also use a waterbrush filled with ink- but I've tried this in the past and have had numerous issues.

Experiment 1:
Ink Used: Platinum Carbon (pigment based fountain pen ink)

I disassembled my Pentel Pocketbrush and applied the silicon grease to the threads on the brush tip and on the body using a clean q tip.  I squeegeed away extra silicon grease using the q-tip, as I did not want it to contaminate the ink.

Using the eyedropper, I filled the body of my Pentel Pocketbrush with ink, and screwed together the two pieces. 

Storing the pen vertically with the brush tip down allows the ink to flow into the brush as it would with a cartridge.

 Once the ink has entered the brush, I've ensured that there are no leaks, and the pen writes, I go ahead and label the pen to prevent any accidental unscrewing.  At first, I tried masking tape, but ended up using an oil based, opaque Sharpie (gold) to write that it's an eyedropper pen, and to write the ink.

Notes:  Platinum carbon ink is VERY gray when applied to a field of color, so I would like to find a darker black for use in eyedropper converted brushpens in the future.

Experiment 2: Colored Ink

Ink Used: Dr Ph Martin's Radiant Concentrated Liquid Watercolor (dye based ink diluted for use as watercolor) in Cherry Red.

I used the same procedure as above, but as the liquid watercolors have eyedroppers, I just used the one that came in the bottle.

Notes:  The undiluted Radiant Watercolor is a little bit gummy in the pen- may need to be watered down a bit.  Very water-reactive (this was the plan). 

In the future, I would love to try shading inks like some of the Noodler's fountain pen inks in a brushpen.

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