When we buy a pen, we often give little thought to the type of ink inside, and how that affects our writing. Well, it turns out there are just a few key factors that can help you make an informed decision the next time you’re shopping in the stationery aisle for a new pen. Let’s take a deep dive into ink, shall we?

Pen inks share two basic components: a liquid base, and a colorant. There are lots of ingredients after that that go into the secret sauce of each manufacturer’s various inks that affect the performance of the ink, but for now, we’re just going to look at these two main components.

The Base: Oil vs. Water vs. Gel

An oil-based ink, which is what you find inside ballpoint pens, consists of dye dissolved in oil. Due to the relative viscosity of oil, the ink runs thicker, and more sludgy. You can almost feel the ink between the pen tip and the paper. Ballpoint pens tend to be quick-drying, and won’t smudge, and because the ink flows slower, they last a long time. Oil-based ink also works on glossy surfaces like magazine covers, or receipt paper because of its adhesive properties.

Water-based ink like that used in rollerball pens, fountain pens, and calligraphy nibs is much thinner than gel and oil-based inks. The liquid ink flows freely, and runs out more quickly, but provides a very smooth, easy writing experience with very little resistance. You get nice even lines that don't break. Water-based inks take longer to dry, and are absorbed into the paper, so they don’t work well on glossy finishes.

Gel ink combines some of the qualities of oil and water by creating a water-based gel that is not as viscose as oil, but thicker than water. The result is a fast-drying ink that won’t smudge, and glides smoothly across the paper. Gel pens come in is a wide array of vibrant colors because gel is a great carrier for pigment particles, and the only base that can carry metallic particles that make sparkly ink.

The Colorant: Dye vs. Pigment

Most inks get their color from either dyes or pigment, or some combination of both. The chief difference between the two is how each reacts when added to a base or solvent. Dye is a colored chemical made to dissolve in liquid while pigment does not dissolve without some kind of binding agent. The pigment particles remain solid, suspended in the carrier. When applied to paper, dye-based inks are absorbed into the material while pigment bonds to the surface rather like paint. In addition having a wider range of colors, pigment is also more water-resistant and fade-resistant than dyes.

Pen Types

Obviously another hugely important factor when it comes to choosing the right pen for the job is the apparatus itself. The actual body and mechanisms determine how ink flows, so let’s take a look at some popular pen types.

Ballpoint Pens

Most modern pens use a similar mechanism involving a tiny ball bearing at the tip of the pen which draws the ink out and rolls it across the paper. Ballpoint pens use an oil-based ink colored with dyes, which tends to be thicker, so the ball bearing typically has a rougher texture for pulling the ink out. More pressure is also needed to dispense the thicker ink, which may be tiresome after long writing sessions.

Rollerball Pens

Rollerball pens feature a similar ball bearing mechanism as the ballpoint pen, but features a water-based ink which writes more like a fountain pen. The liquid ink flows easily so these pens tend to have a smaller ball at the tip with a smooth surface. It is very easy to write with a rollerball and requires little pressure. However, the ink flows more quickly, therefore these pens tend to have a larger reservoir holding more ink, and costing more dollars.

Gel Pens

Perhaps the most versatile pen, gel pens come in a dizzying array of colors with special effects like metallics, neon colors, and pastels. The gel ink also finishes opaque on the surface, which allows ink to show up on dark paper. It also lasts longer than rollerball, and writes more smoothly than ballpoint. And given its low viscosity, comes in a range of point sizes including extra fine.

Fountain Pens

Unlike our previous pens, fountain pens rely on capillary action for ink to flow through a feed. They take water-based ink with colors coming from dyes because the solids in a pigment ink can clog the tip and ruin the pen. They are usually refillable, and ink comes in cartridges or bottles. The ink is very watery, so these pens are prone to splashing and leaking. It takes some practice to write with a fountain pen.

Calligraphy Pen, or Dip Pen, or Pointed Pen

A dip pen or pointed pen involves a metal nib attached to a holder. The nib is repeatedly dipped into ink during the writing process. This type of pen is most often used for calligraphy. Calligraphy ink looks a lot like fountain pen ink, however it is often colored with pigment instead of dye. Truly, you can use almost any kind of ink with a dip pen, which makes it so much fun to experiment.

Specialty Inks

There are a few honorable mentions in the specialty category of inks.

Hybrid Ink

While there is no standard definition for hybrid ink, it is generally known to be a blend of water and oil based inks with the purpose of achieving some of the best qualities of each. Hybrid inks, like the ones used in the Uni-ball Jetstream series or Zebra’s Surari offer the quick-drying, smear-resistant qualities of ballpoint pens, with better color saturation and smoothness of gels.

Rapid Dry Ink

Just like the name implies, rapid dry inks dry fast. Zebra’s Sarasa Dry pens dry in under one second on most paper surfaces, perfect for left-handed users.

Iron Gall Ink

A traditional ink sometimes known as registrar’s ink, iron gall is made with gall from oak trees which contains iron, hence its name. This type of ink is typically blue, and very permanent, which is why it is commonly used for official records such as marriage and birth certificates.

Metallic Ink

Also known as sparkle ink, this is a gel ink with powdered aluminum added.

Erasable Ink

Erasable pens commonly use one of two types of thermo-sensitive ink. One is made with liquid rubber cement which dissolves when it reacts to the heat generated by rubbing the eraser on the paper. The other uses pigment called thermochromic ink that turns clear in reaction to heat. This is handy for taking notes, but beware, the ink could disappear in extreme heat!

So with that primer on ink and pen types, go out and find the 'write' pen for you!