Finding a waterproof fountain pen ink can be tricky, but JetPens has tested each and every one of our more than a thousand fountain pen inks to determine which inks won’t wash away. If you’re looking for a waterproof ink, you don’t even need to sacrifice ink color selection. Read on for our waterproof fountain pen ink recommendations.
An important use case of waterproof inks: art! Some artists enjoy using Platinum Carbon Black with watercolor paints. We don’t necessarily recommend it for quick en plein air painting because the ink requires a few hours to fully “cure,” but you can always draw a scene and paint over it from a reference picture later.
“Water-resistant” ink, meanwhile, will either blur in a water dip or smear enough under a brush that it outweighs perfect dip resistance. In either case, lines should remain legible.
In this guide, most inks are pigment based, colored with tiny insoluble chunks of color that snag in paper fibers. Pigment ink calls for a more regular pen cleaning schedule, but is much more durable on the page. We test inks on smooth Rhodia DotPad paper, so our pigment ink recommendations may actually be even more waterproof on toothier paper.
We found Rohrer & Klingner sketchINK Fountain Pen Inks to be another extremely strong option. These inks are solidly waterproof even with almost no time to cure, they don’t feather, and they cover a great range of colors. That said, they lack true primary colors and can’t be mixed to the same vibrance as the De Atramentis inks.
Another option are rich Sailor Pigment Inks, which have a simple, classic color range of black and two different blue-blacks. They’re more easily activated by water and smear a little more dramatically than the Kala Nostalgia inks, but remain legible overall.
Tests were done using Rhodia DotPad paper and a TWSBI ECO 1.1 mm fountain pen dipped in ink. Soak tests were performed by dipping writing samples in water for 30 seconds. This test shows how much the ink will run or fade when left soaking in water. Brush tests were done with a Kuretake medium water brush. This test shows how prone to smearing from a wet finger or brush the ink is. It can also reveal the various component colors the ink is made up of. All writing samples were allowed to dry for at least 24 hours before testing to achieve maximum water resistance.
Highlighter tests were also done on Rhodia DotPad paper with a TWSBI ECO 1.1 mm fountain pen. The highlighters used were the Stabilo Boss ink highlighter and the Monami Essenti Dry gel highlighter. The thin strokes of the 1.1 mm nib are comparable to writing from a fine nib, and the wide strokes are comparable to writing from a broad nib. Rhodia paper is very smooth and non-absorbent, allowing inks to smear more easily on it than they do on other, toothier papers. Because of this, you may experience better results if you use a toothier, more absorbent paper.
As we mentioned above, there’s a lot out there to learn about what goes into inks. Read on for a more detailed explanation of ink types.
The downside to using bulletproof inks is that they don’t fare as well on smoother paper like Rhodia or Tomoe River. Smooth paper doesn’t allow the ink to fully absorb into the fibers, and any bulletproof ink left sitting on the surface of the paper can take a very long time to dry and will remain susceptible to water even after it dries.
Some Noodler’s inks are “partially bulletproof,” meaning they contain a mix of bulletproof and non-bulletproof dyes. These inks tend to perform better on smooth paper, but the tradeoff is that the water-soluble portion of the ink will flee when exposed to water, fading and smearing around the the waterproof “core.”
The downside of pigment-based inks is that they require a stricter cleaning regimen than dye-based inks. If a pigment-based ink is left to dry inside a pen, the pigment particles can clog up the feed. And since the pigment particles aren’t water soluble it can take a lot of work to flush them out of the feed once this happens.
When using pigment-based inks, we recommend cleaning your pen once a month, plus any time you don’t expect to use the pen for more than a week.
Pure iron gall ink is clear when wet and turns dark gray over several minutes as it dries and oxidizes. To make them easier to see when wet and more appealing to read when dry, iron gall inks are mixed with dyes to give them color.
A typical iron gall ink like Diamine Registrar’s Ink will start off as a light blue when wet and transform within minutes into a dark blue black. The dyes used to color the ink may run or fade when wet, but the dark gray lines that the iron gall particles make will remain sharp and clear.
In addition to being waterproof, iron gall inks tend to be dry-writing and very well-behaved, making them a good choice when using wetter pens or less fountain pen friendly paper.
So if iron gall inks are so great, why don’t we see more of them around? The main reason is that they’re acidic. If you open a medieval book written in iron gall ink, you may find pages filled with letter-shaped holes as if the letters were cut out of the page with a laser. Plenty of medieval iron gall writings have fared much better, however, and modern iron gall inks are far gentler than their medieval forebears. In some countries iron gall inks remain the preferred ink for signing legal documents due to their permanence. Still, you may want to stick with a pigment-based ink if you find the thought of your words crumbling away after a mere few centuries disturbing.
A more immediate concern with iron gall inks is the possibility of the ink corroding steel nibs. We’ve never seen a confirmed case of this happening ourselves, but we do recommend cleaning your pen regularly to be safe.
1 Oak apples are round growths found on a variety of oak trees. They are caused by chemicals released when a gall wasp lays its larva inside a developing leaf bud. ↩