How lightfast is pigment ink?

My current favorite for use in fountain pens. Made with their ‘nano’ pigment formula, it’s wonderfully smooth and well-behaved in even extra-fine nibs, and it dries to a dense, matte-finish black. Pigment inks can clog up pen feeds, but I’ve never had any flow issues or hard starts, ever, with this ink. I’ve found that Sailor’s dye-based inks tend to be on the dry side (not a bad thing - I like the shading and feedback), but their pigment inks have a surprisingly wet flow. Kiwaguro dries somewhat slowly, but fast enough that I can write without smearing it, especially if I use a finer nib.

My only gripe with this ink is that it’s not completely waterproof. It will stay put if you drip water on the paper, but if you run a wet brush over it, it will smear pretty quickly. I can’t, for instance, draw some lines with this ink and then add a watercolor wash.

Another old favorite and arguably the classic of black archival inks. It dries to the darkest black of any of the inks I own, and has a beautiful shiny finish. Unfortunately it’s more temperamental than Kiwa-guro. I've had flow issues with it in pens before, with occasional clogging and hard starts — a symptom, I think, of the larger pigment particles it uses to achieve that wonderful dense black.

It also takes forever to dry. I don't have an exact number but it's usually minutes, not seconds. Being left-handed, it can be difficult for me to write with this ink because I end up smearing it. Thicker, more absorbent papers and dry nibs (e.g. extra fine) help with this, but it can tricky regardless.

Once it finally dries, it's very water-resistant, holding up even to wet brush strokes.(Note: I find if I wet my finger and rub it hard across a line repeatedly, it will start to smudge. But it seems to handle light brush strokes fine, as long as you don’t ‘worry’ it too much.)That makes it a wonderful drawing ink. I use it often with my brushes and brush pens, especially for detailed linework.

I love Rohrer & Klingner’s inks. Their dye-based fountain pen inks are some of my all-time favorites. I also like that they offer weird stuff almost no one else does, like iron gall inks. Their ‘Sketch’ line of pigment-based inks is relatively new and I’ve really liked them so far. They offer a surprisingly wide range of colors, each with a ‘person’ name and a sketched portrait on the label. Lotte is black, Lilly is brown, Thea is a cool gray, Emma is green, etc.

Lotte is labeled as black but it actually dries to more of a dark gray with a purplish cast. I wonder if these inks have fewer pigment particles per volume than, say, Sailor’s or Platinum’s, to help with flow in pen feeds. All of the colors are fairly muted and light, often with significant shading. I find this quirk helpful; the low-density tones are easy to control and I often use Lotte and Thea for shading and light washes.

I also appreciate that Sketch inks dry relatively quickly and are quite water resistant.

I realized I should add a couple of controls to my experiment. For the first, I’ll use Speedball’s traditional india ink, using carbon (wood soot) pigments in a shellac base. This is an archival drawing ink and an old favorite. It dries to a matte black slightly lighter than Platinum Carbon Black or Sailor Kiwaguro. It’s not safe for fountain pens, but it’s a fantastic ink to use with brushes or dip pens. It’s relatively inexpensive, easy to find, archival, and well-behaved on all kinds of surfaces.

As another control, I thought I should test a traditional dye-based fountain pen ink. Graphite is a black with a lovely, complex greenish undertone. Used with a broader nib on good paper, there’s lots of beautiful shading and chromatic shifts.

Graphite is not water resistant at all, and has no claims of being lightfast. So I figured it would offer a good benchmark for dye inks. I expect it to fade noticeably after a couple months in sunlight, but we’ll see.

I made two swatches for each ink. One swatch will be kept in a closed notebook in a drawer, away from sunlight. The other will be taped to my office window, exposed to as much sunlight as possible. My office faces southeast, and it’s early spring. My swatches should get pretty fried through the summer.

About once a month, I’ll pull out the ‘dark’ and ‘light’ swatches for each ink and compare them side-by-side. I’ll update this post with new photos each month.

I marked the ‘dark’ swatches with a D in the upper right corner, and the ‘light’ (exposed) swatches with an L. Here’s how all the swatches look at the starting line. The ‘dark’ swatches are on the left, the ‘light’ on the right.

Robert Oster's Graphite (the dye-based ink, my 'control') is starting to fade noticeably. The others still look good so far.

At this point, Robert Oster's Graphite is not even recognizable, reduced to a sepia. The others are holding strong, although I think I might see a hint of discoloration in the Sailor Kiwaguro - but it's hard to say yet.