Review: Kuretake ai Liner brush pen

“Oh, I have a random brush pen for you,” a friend said recently, handing me a new in-package Kuretake ai Liner without further explanation. So here we go!?

The Kuretake ai Liner is a compact, disposable pen featuring an ultra-fine, bristle-tip brush “similar to those found in eyeliner cosmetics.”

The pen has no roll stop, and the cap doesn’t post. I’m guessing this is all to mimic eyeliner tools, but these properties are all annoying for a pen. At 4.75″ capped, the pen is indeed compact. Uncapped, it’s exactly 4″, not counting the 0.25″ long brush tip.

For comparison, standard pens are around 5.5″ capped, 5-5.25″ uncapped, and 6-6.5″ posted. Asian calligraphy pens tend to be longer, around 7″ capped, 6.5″ uncapped, and up to 8″ posted.

The Kuretake ai Liner is apparently within a fairly standard range for compact/pocket pens, but I haven’t had a lot of experience with this size of pen. I don’t think I like it. It’s uncomfortable to use for long periods of time, at least for me. My hand feels like it cramps faster.

Maybe it’s a psychological thing though? The ai Liner is still a standard diameter, and an extra inch and a half off the back of the pen doesn’t affect much but the weight of it — a standard sized pen feels more balanced, but it isn’t like I’m gripping the shorter pen in a different spot or anything. Maybe it’s something to get used to, but I really wish I could at least post the cap.

Having no experience with fine brush eyeliner pens, I can’t say whether the Kuretake ai Liner’s brush tip is similar or not, but it’s definitely a delicate, ultra-fine brush.

Since all bristle-tip brush pens comprise of individual bristles, it’s generally possible to get extra thin lines with them as long as the brush tip holds together and retains its point well, but it requires a high level of practice and precision. You have to have excellent pressure control and be able to create just the smallest amount of contact between pen and paper. It can also be harder to get fine lines if a brush is dense and if ink flow is heavy and wet.

The Kuretake ai Liner’s brush is thin and has low bristle density: this means fewer individual bristles make up the brush tip, making the point smaller by default. It also means the brush can hold less ink, so ink flow tends to be less heavy.

Quick, thin lines — like for whiskers or eyelashes — are pretty easy with the Kuretake ai Liner, but shorter, more precise ones, especially if you need careful curves — like maybe for snowflakes or small circles — are a lot harder.

The thin brush tip is extra flexible, which makes it harder to control. You’re better off with a fine, felt-tip brush pen, like the Tombow Fudenosuke, for finicky detail work.

The Kuretake ai Liner, naturally, performs less well for broad strokes.

It deposits less ink, so thicker and longer lines run dry faster. This is what made the Akashiya Sai ThinLine work so well as a “dry brush” pen, though it wasn’t nearly as good as the ai Liner at making actual thin lines.

The brush also doesn’t snap back into shape as well when used for thick lines, since you’re applying more pressure to the bristles, flattening them against the paper. The lower bristle density gives less protection to individual bristles, so it can be easy to bend them in different angles. Be sure to have a scrap sheet nearby on which you can reshape the brush tip lest the bristles get stuck that way.

I don’t really think the “dry brush” tendency of thin/low density brushes is a weakness so much as something to be aware of. It can add a nice effect to drawings, but if you want to be able to do wetter broad strokes, it’s better to switch to a less specialised brush.

Like most of Kuretake’s other disposable pens (and unlike it’s cartridge-fill brush pens), the ink in the ai Liner is water- and pigment-based and waterproof, as well as alcohol-proof, so you can use it with a variety of coloring tools.

Though the ink flow is mild, the ink itself is fairly wet and depending on the paper, prone to smearing. On smooth Bristol board, it can still smear pretty badly even after 15 seconds, but on cardstock, it’s relatively safe to touch after 4-5 seconds. It absorbs into index cards quickly and won’t smear much after 2 seconds.

The Kuretake ai Liner is exactly what it says it is: an ultra-fine brush that’s great for thin lines, though detail work can still be challenging depending on what it is.

The pen’s compact and light, but I think that’s a con more than a pro. It’s not as good with thick strokes and black fills as a more standard brush pen might be.

At $9.99 MSRP and ~$7.50-8.00 actual sale price, it’s pretty pricy for a disposable, but not out of bounds for a bristle-tip disposable. The Copic Gasenfude, probably the most notable pen in this tiny, tiny category, is similarly priced. The ai Liner is definitely more specialised than the Gasenfude, so which is better depends largely on your intended use and personal preference.

The Akashiya Sai ThinLine more directly competes with the ai Liner and it’s notably cheaper, but its performance is poorer in pretty much every aspect too (though it’s full-length pen, which is nice).

There are numerous refillable bristle-tip brush pens in the $7-13 price range though. None of them sport the ultra-fine brush of the Kuretake ai Liner, but they’re more solid all-rounders, so I wouldn’t recommend the ai Liner unless you have a really specific use case and need those easy thin lines.