If you journal with watercolor, the Pentel Aquash water brush is probably worth carrying. If you need precise control or waterproof linework, it’s a gamble.
I review about 200 unique writing instruments and art supplies every year for our procurement team—testing for consistency, reliability, and how well they hold up in real-world use. In Q4 2024 alone, I rejected 18% of first deliveries from new vendors because of barrel cracks or nib inconsistencies. So when I say a tool works for journaling, I mean it survives a 50-page sketchbook without leaking or degrading.
The Aquash water brush is a refillable brush pen with a water reservoir in the barrel. You fill it with clean water (or diluted ink), squeeze gently, and water flows to the brush tip. It’s popular among watercolorists and journalers. I’ve tested maybe 15 units across four batches over two years—some from Amazon, some from art stores—and I’ve used it in hotel rooms, coffee shops, and outdoor sketching sessions. Here’s where it excels and where it doesn’t.
The Aquash is fantastic for loose, flowing washes and quick studies. But if your style demands hairline detail or crisp edges, you’ll fight it.
What the Aquash Does Well
For journaling—especially travel journaling—the convenience is hard to beat. You don’t need a separate water cup. You don’t need to dip. You just squeeze and paint. That means you can work in a cramped airplane seat or a park bench without spilling a jar of water over your sketchbook. I’ve done exactly that: flying back from a trade show, sketched notes in a Leuchtturm1917 with the Aquash and a small palette of watercolor cakes. No spills, no drama. That’s its superpower.
The flow is also adjustable. A light squeeze gives a dry brush effect; a firmer squeeze floods the tip for broad washes. I’ve found the middle pressure yields the most consistent flow—heavy enough to activate watercolor cakes, but light enough not to oversaturate cheap cartridge paper. Not ideal for heavy soaking techniques, but workable.
The Real Test: Consistency Over 50 Pages
I ran a blind test with our design team: six people, six identical Aquash brushes, each filled from the same distilled water bottle. We sketched the same scene (a simple coffee cup) on three different paper types—Rhodia 80gsm, Canson Montval 300gsm cold press, and generic copy paper—and rated flow consistency, leakage risk, and nib durability.
Results: 4 out of 6 rated the Aquash as “consistent enough for journaling” across all three papers. The other 2 noted nib fraying after the test on the copy paper (which is rougher and more abrasive). On the Canson paper—closer to what a serious journaler might use—the brush performed better, with minimal fraying. The cost difference? About $1.50 per brush versus a traditional dip water brush plus cup. On a 500-unit sample, that’s $750—for measurably less hassle and zero spill risk.
But—and I hesitated to include this because it’s an outlier—one unit from the Amazon-bought batch had a defective barrel seal. It leaked water into the cap during transit, which ruined the brush tip and stained the cap. That’s a 6-7% defect rate in my small sample. Pentel’s quality control is generally solid, but I’d recommend buying from a reputable art supplier rather than a generic third-party listing.
Where the Aquash Falls Short
If you need fine lines—thin, precise, like a fountain pen tip—this brush won’t deliver. The Aquash’s smallest nib (the “fine” tip) is still a brush, not a needlepoint. It produces variable lines that can look great for expressive sketches but frustrating for detailed botanical studies or architectural notes. I’ve seen people try to compensate by squeezing harder, which just floods the paper. No bueno.
Also, if you’re working with a traditional hardbound journal that only opens 180 degrees, the brush angle can be awkward. The barrel is thick (about the size of a Sharpie), so it doesn’t nestle in a pencil grip the way a thin marker does. I’ve learned to hold it farther back, near the reservoir cap, to get better control. Your mileage may vary—especially if you have smaller hands.
Finally, the nib isn’t replaceable. Once it frays or gets damaged, you toss the whole brush. That bothered me because Pentel makes brilliant mechanical pencils—the GraphGear 500 is a masterpiece of precision engineering—and this brush feels less thoughtfully designed. It’s a tool, not an heirloom. At $6-8 a unit, it’s affordable enough to replace every 3-6 months with regular use.
Who Should Buy It (and Who Shouldn’t)
I recommend the Aquash for journalers who prioritize portability and loose, expressive marks. If your journaling style leans toward bold washes, abstract landscapes, or simple diary sketches with color, this brush will serve you well. It’s also good for beginners who want to experiment with watercolor without buying a full setup.
If your style demands tight control—think botanical illustrations with tiny veins or architectural elevations with clean edges—I’d look at a refillable water brush with a finer synthetic tip (like the Koi water brush, though I won’t name brands). Or go back to a dip brush with a separate water container. The Aquash isn’t wrong for those uses; it’s just not optimal.
And if you’re buying for a classroom or a group workshop, I’d order a spare unit or two to account for potential defects. That 6-7% failure rate isn’t catastrophic, but it stings when you’re counting on a kit arriving complete.
One Last Thing: The pH Myth
A quick note: I’ve seen artists claim the Aquash’s plastic body leaches chemicals into the water and affects paint color. I tested this—left distilled water in a new brush for 72 hours, then measured pH with a standard aquarium-grade meter (Hach brand, calibration verified). Results: pH 7.1–7.2, essentially neutral. The water looked clear under a 40x loupe. No discoloration, no chemical smell. If you’re genuinely worried, use distilled water and rinse the barrel before first use. But the fear is, in my experience, overblown.
Bottom line: the Aquash is a good tool with clear trade-offs. It’s not the “best” water brush for everyone—but for journaling on the go, it’s one of the most convenient. I keep one in my everyday carry bag, and I don’t regret it. At least, not yet.
