Understanding Ink Properties

Fountain pen ink is far more nuanced than the black or blue cartridge ink most people grew up with. Modern fountain pen inks come in an enormous range of colors, behaviors, and special properties. Understanding these properties will help you choose inks that perform the way you need them to — whether you're writing everyday notes, addressing envelopes, or creating art.

What Makes Fountain Pen Ink Different

Fountain pen inks are water-based dye solutions specifically formulated to flow through the narrow channels of a fountain pen's feed system. Unlike ballpoint ink (which is oil-based and viscous) or India ink (which contains suspended particles and binders), fountain pen ink is thin, free-flowing, and designed not to clog.

This water-based formulation means fountain pen inks dry through absorption and evaporation rather than chemical curing. It also means they interact with paper differently — the ink is drawn into the paper fibers, which is why paper quality matters so much for fountain pen users.

Color and Saturation

The most immediately noticeable property of any ink is its color. But color alone doesn't tell the whole story — saturation describes how intense or vivid the color appears on paper. A highly saturated ink produces deep, rich color; a less saturated ink appears lighter or more muted.

Saturation is affected by several factors: the dye concentration in the ink, the wetness of your pen (how much ink it lays down), the nib width, and the paper you use. A broad, wet nib on absorbent paper will produce a very different result from a fine, dry nib on coated paper — even with the same ink.

When browsing inks online or using tools like InkPalette, keep in mind that digital color representations are approximations. The actual appearance of an ink on paper depends on all of the factors above. That said, digital swatches are very useful for narrowing down your options before buying a sample.

Water Resistance

Most fountain pen inks are not water-resistant. If water hits the page, the ink will smear or wash away. For everyday journaling or note-taking, this is rarely a problem. But if you're addressing envelopes, writing important documents, or working in environments where moisture is a concern, water resistance matters.

Water-resistant inks use different chemistry to bond with paper fibers. Some common approaches include:

• Pigmented inks: Contain tiny solid color particles that settle into paper fibers. Examples include Sailor Sei-boku and Platinum Carbon Black. These are highly water-resistant but require more frequent pen cleaning.
• Iron gall inks: Use an iron compound that reacts with paper cellulose to create a permanent bond. Classic examples include Rohrer & Klingner Salix and KWZ Iron Gall inks.
• Cellulose-reactive dyes: Some inks use dyes that chemically bond with paper fibers. Noodler's "bulletproof" line is a well-known example.

Shimmer and Sheening Inks

Two of the most visually striking ink properties are shimmer and sheen. Though often confused, they're quite different phenomena.

Shimmer

Shimmer inks contain fine metallic or mica particles suspended in the ink. These particles catch light and create a glittering effect on the page. Popular shimmer inks include Diamine's Shimmertastic line (like Enchanted Ocean and Golden Sands) and J. Herbin's 1670 Anniversary inks.

Shimmer inks work best with medium or broad nibs — fine nibs can filter out the particles. They also require more frequent pen cleaning, as the particles can settle and clog the feed over time. Many enthusiasts keep a dedicated pen for shimmer inks.

Sheen

Sheen is a natural optical property where excess dye on the paper's surface reflects a different color than the base ink. For example, Organics Studio Nitrogen is a deep blue ink that sheens a vivid red-copper. Sailor Yama-dori is a teal that sheens a rich magenta.

Sheen is most visible on smooth, non-absorbent paper (like Tomoe River or Graphilo) with a wet pen. On absorbent paper, the dye is pulled into the fibers before enough accumulates on the surface to produce the effect. Unlike shimmer, sheen doesn't require particles, so it won't clog your pen.

Iron Gall Inks

Iron gall ink is one of the oldest ink formulations in history — it was the standard writing ink in Europe for over a thousand years. Modern iron gall fountain pen inks retain the core chemistry but are formulated to be safe for fountain pens.

These inks start lighter when first written and gradually darken over hours as the iron compound oxidizes. The result is a permanent, water-resistant line that darkens beautifully over time. Many users love the unique character of watching their writing transform.

Drying Time, Flow, and Feathering

Drying Time

Drying time varies widely between inks — from a few seconds to 30 seconds or more. Fast-drying inks are practical for left-handed writers and anyone who tends to smear their writing. However, very fast-drying inks can sometimes feel drier or scratchier because they contain less lubricant. Some inks are specifically marketed as quick-drying, such as Pilot Iroshizuku Take-sumi and Rohrer & Klingner Verdigris.

Flow

An ink's flow describes how wet or dry it feels in the pen. A "wet" ink flows freely and lays down a heavy, saturated line. A "dry" ink is more restrained and produces thinner, less saturated lines. Flow is influenced by both the ink's formulation (viscosity, surface tension) and your pen's characteristics. A wet ink in a dry pen (or vice versa) can balance each other out.

Feathering and Bleed-Through

Feathering occurs when ink spreads along paper fibers, creating fuzzy or spidery edges around your writing. Bleed-through is when ink soaks completely through the paper and is visible on the back side. Both are primarily paper-dependent — high-quality, fountain-pen-friendly paper like Rhodia, Clairefontaine, and Tomoe River are designed to minimize both. Using a finer nib and a less wet ink can also help.

Inks to Avoid in Fountain Pens

Not all inks are safe for fountain pens. Using the wrong type can permanently damage your pen's feed and nib assembly.

Always look for inks explicitly labeled as "fountain pen ink." Reputable fountain pen ink brands include Pilot Iroshizuku, Sailor, Diamine, Rohrer & Klingner, KWZ, Robert Oster, and many more.