If you’ve spent any time in art supply circles online, you’ve probably seen the videos. Someone holds up a dried-out Posca, removes the nib, squirts in some ink, reassembles it, and the pen writes like new. And the comments are always the same: does this actually work?
Three of my black Posca PC-1Ms ran out of ink this week. (From all the automatic drawing!) I use Montana Shock Black ink in my 15mm and my 3mm pens which are designed to be refillable. I have always wondered about refilling a Posca and someone sent me one of those “Posca Hack” videos and I decided to try it.
It worked! Here’s exactly what I did.
Why This Even Comes Up
Posca pens are paint markers, not ink pens, which means when the paint runs out, the conventional wisdom has always been: that’s it, toss it, buy a new one. The Internet lore was that the pen was sealed and since Posca doesn’t sell their ink separately, the formula is proprietary, and everyone was always looking for a refill hack.
But acrylic paint markers are refillable in principle, if you can get them open and find an ink that works with the valve system and nib material. That’s the part the videos gloss over. The technique is simple. The ink choice matters more than people admit. (FYI, you can also buy empty pens with a variety of nib styles and sizes — more on that in the full video below.)
Step-by-Step: How to Refill a Posca Pen
- Twist the top of the pen with the nib mechanism off, turn it the wrong way on purpose. Posca nibs are counter-threaded, which means the normal righty-tighty, lefty-loosey rule works in reverse. If you twist the way instinct tells you, you’ll just lock it tighter. Go the opposite direction: twist right to loosen.
- For a better grip, use a pair of pliers. A paper towel protects the pen from the plier teeth. (I wish I had thought of this before I started!) Twist right, pull steady, and it will release. Set the nib somewhere it won’t roll off your table. Ask me how I know.
- Add your ink. Carefully add ink directly into the barrel. For a PC-1M, I used about 1–1.5ml. Don’t overfill. You want room for the nib and the ball to do their job.
- Replace the nib. Press it back in and twist to tighten — remember, counter-threaded, so twist left to lock it back down.
- Shake and prime. Cap the pen, shake well (just like a new Posca), then press the nib down on scrap paper until the ink flows through. This may take a few presses. Be patient. If you overfill the pen, there will be a giant blob of ink, so make sure you are on a test page.
- Test it. Draw some lines, circles, a word. Check that coverage is consistent and the nib isn’t scratching.
That’s it. Mine wrote beautifully.
Want to see the full process, including how refillable pump markers work and why the ink choice matters? I cover all of it in the 10-minute version on YouTube.
What Inks Work (and Why It Matters)
Posca doesn’t sell their own refill ink, which means you’re choosing a substitute. These are the two most recommended options, and what I know about each.
Montana Cans acrylic ink (what I use) Montana’s acrylic inks are formulated for marker systems, which means they’re designed to flow through a valve and nib without clogging. The viscosity is calibrated for this kind of delivery. Shock Black is highly pigmented and matte. [Link to Montana acrylic ink]
Golden High Flow Acrylic Golden is a longtime favorite in the mixed-media world. Their High Flow Acrylic line is designed to have the consistency of ink while delivering the opacity and permanence of acrylic paint. Several people in the journaling and lettering community have had good results using this to refill Poscas. It comes in a wide color range. [Link to Golden High Flow]
What to avoid: Heavy-body acrylics, gouache, anything with a thick or gummy consistency. These will clog the nib and you’ll have a bad time. And yes, that includes the tempting shortcut of watering down craft store acrylic paints like Apple Barrel or Folk Art. It seems logical, but thinning those paints doesn’t replicate the chemistry of a properly formulated acrylic ink. The pigment load is different, the binder ratio is different, and you’re likely to end up with something that either clogs the nib, dries patchy, or refuses to flow consistently. Use ink that was actually designed to move through a marker system.
A Little Science: What Is Acrylic Ink, Exactly?
Acrylic ink is a pigment suspended in an acrylic polymer emulsion, which is essentially water-based plastic. When the ink hits air, the water evaporates, and the polymer chains link together to form a flexible, waterproof film. That’s why acrylic paint and ink are permanent once dry but water-soluble while wet.
In a paint marker like a Posca, the same chemistry applies. The pigment is held in suspension by the emulsion, kept moving by the mixing ball inside the barrel, and delivered to the nib by valve pressure. This is also why the refill works: any acrylic ink with the right viscosity can move through the same system.
The key word is viscosity. Too thick and it won’t flow. Too thin and it floods the nib and bleeds. Inks made specifically for markers (like Montana) are engineered for this. High Flow acrylics (like Golden) are also thin enough to work. Standard fluid acrylics are a maybe. Heavy body acrylics are a hard no.
Everything I Used + Links
- Posca PC-1M (extra-fine) [link]
- Montana Cans Shock Black Acrylic Ink [link]
- Golden High Flow Acrylic (alternative) [link]
- Molotow 1.5 mm and 4 mm tips Refillable Marker [link]
- Molotow 15 mm Refillable Marker [link]
This post is part of an ongoing deep dive into acrylic pens and markers.✨ Subscribe to my YouTube channel for immediate notifications
Final Thought
It was so satisfying to finally test this out. It solves my ongoing hunt for more reusable supplies that I can refill. Some people will be annoyed by the occasional mess and the need to shake these pens regularly. That’s just the nature of pigment-based inks — the pigment and binder separate as the pen sits or as you use it, so a good shake is part of the deal. The Montana Shock Black is a bit darker than the Posca ink, so this is a complete delight to be able to have that ink in the fantastic little PC-1M form factor.
