Pigment vs Dye Fountain Pen Ink, Explained

Most fountain pen ink you'll ever meet is dye-based. It flows well, comes in every colour imaginable, and rinses off your hands with a bit of soap. That last part is also the problem. Pigment fountain pen ink solves it in a completely different way, and the difference matters the moment a splash of water lands on something you wrote a year ago.

Here is what the two types actually are, how they behave on the page, and how to look after the pigment kind so it can look after your writing.

What dye ink is doing

Dye ink is colour dissolved into liquid, right down to the molecular level. Those molecules soak into the paper fibres, which is why dye inks are so vivid and why they shade the way they do, pooling darker wherever the nib lingers. They pass through even a fine nib without complaint.

The catch is baked into the chemistry. Anything that dissolves can be re-dissolved, so water lifts a dye straight back off the page. Ultraviolet light slowly breaks the molecules down too, so a dye-inked page left in a sunny spot will fade over the years. For most everyday notes none of that matters. For a signature or a journal you want to keep, it does.

What makes pigment fountain pen ink different

Pigment ink suspends solid colour particles in the liquid rather than dissolving a dye. Those particles are far bigger than dye molecules, still ground fine enough to travel through a nib, but big enough that once the water carrier evaporates they settle on and in the paper as a physical layer. That one change does all the work. A solid particle cannot be washed away by a splash of water the way a dye can, and it stands up to light far better.

Sailor has built much of its reputation on this. The company was founded in Hiroshima in 1911 and is one of Japan's three great pen makers, alongside Pilot and Platinum. Its pigment inks, sold as cartridges in our inks and refills collection, are the ones we reach for when the writing needs to outlast the notebook.

Water resistance and archival writing

Once dry, a pigment line is waterproof and fade-resistant. Run a damp finger across it and the mark stays put. Leave it in the light for a decade and it holds its colour. This is what people mean by archival writing, and it is why pigment ink suits signatures, formal correspondence, artwork and any journal you actually intend to reread.

The phrase to hold onto is once dry. Before it sets, pigment ink behaves like any other wet ink, so give a fresh page a minute before you close the cover or drag your hand across it.

The catch: don't let it dry in the pen

The property that makes pigment ink so tough on paper works against you inside a pen. Because it is a suspension of solids, a pigment-inked pen left unused for weeks will let its water evaporate and its particles settle and dry in the feed. The result is a pen that skips, or worse, one you have to soak to revive.

None of this is dramatic, and dye inks want looking after too. The rule of thumb is simple: use a pigment-inked pen regularly, flush it with water before you switch to a different ink, and don't fill a pen you know you won't touch for a month. Treat it like a working tool rather than a shelf ornament and it will behave.

Cartridge or converter

Sailor's pigment inks come as cartridges, so the easiest way in is to drop one into a Sailor body and start writing. A converter lets you fill from a bottle instead, which is handy for bottle colours, though with pigment we lean towards cartridges for anyone who writes in bursts rather than daily. A sealed cartridge holds less standing ink to dry out and is simply less to manage.

If you want a pen to pour it into, Sailor's Fude De Mannen is a lovely match, its bent brush-style nib turning a single stroke from hairline to bold by tilt alone. It moves in and out of stock, so it is worth watching for a restock, but you'll find plenty of other options in our pens and pencils range in the meantime.

Where to start: Kiwaguro, Seiboku, Souboku

Sailor's pigment cartridges come in three shades, and the names describe the depth. Kiwaguro (極黒, "extreme black") is the densest, an opaque true black made for signatures and anything that has to read as properly black. Seiboku (青墨) is a blue-black that reads blue in the light and black at the edge of each stroke. Souboku (蒼墨) is the deeper of the two blue-blacks, near enough to black in normal light until you catch the wet part of a line and the blue shows through.

If you are new to pigment ink, we would start with the Seiboku rather than the pure black. A blue-black forgives the odd feathery stroke better than a flat black does, and it is the most versatile of the three to live with day to day. Keep the Kiwaguro for when you want maximum contrast, and pair the Souboku with a fude nib if you like dramatic line variation.

One last thing that sits outside the ink itself: paper carries as much of the result as the ink does. A pigment line looks its best on a smooth, well-sized sheet that lets it sit on the surface, so it is worth reading our guide on how to choose a Japanese notebook before you commit a favourite ink to a page you'll want to keep.