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Kuretake No. 13 Brush PenI've been a brush pen user for years. I love them. They're my primary sketching tool & I always have at least one in my bag and one in my car. My first was the Pentel Pocket Brush. From there I moved on to the Pentel Standard Brush and the Kuretake No. 8. Then I was given a Kuretake No. 13.
I still have all the others, and still use them, but the Kuretake No. 13 is the finest of the lot. Being able to move, in one stroke, from a thin, fine line to a fat, smushed line is what makes all brush pens so fun. Even my least favorite brush pen is a blast to use but it's the Kuretake that gives me the most control. My thin lines are thinner, my fat lines are more consistent and I get more variety between the two than with any other pen. Further, after a broad, smushed stroke, the bristles return to shape immediately, allowing me to move onto a more delicate line without having to dab the brush back into shape on a piece of scrap paper.
Further, the ink flow is just right. A lot of brush pens, with a full ink cartridge, have a tendency to be "wet." When you press the bristles down for a fat line, the ink can puddle on the page, leaving a shiny wet line just begging to be smeared across your sketch. Great, if that's the effect you want. I rarely do. I like an ink line that's controllable and dries quickly enough that I can move around the page without worrying too much about where to put my hand.
The pen uses water-based dye ink refill cartridges and the default ink is just a bit blacker than the default Pentel ink & reacts similarly with water. Because I've ruined two Pentel brush pens trying DIY refilling tricks, I've no idea how well the Kuretake reacts to other inks. If someone wants to try it, please let us know how it goes.