Gel ink pen

A gel pen uses ink in which pigment is suspended in a water-based gel. Because the ink is thick and opaque, it shows up more clearly on dark or slick surfaces than the typical inks used in ballpoint or felt tip pens. Gel pens can be used for many types of writing and illustration.

The general design of a gel pen is similar to that of a regular rollerball pen, with a barrel containing the writing mechanism and a cap, and a reservoir filled with ink. The barrels can be created in many different sizes and designs; some have finger grips of rubber or plastic. The size of the nib or pen tip ranges from 0.18 millimetres (0.0071 in) to 1.5 millimetres (0.059 in).

Compared to other inks, gel ink has higher viscosity, which supports a higher proportion of pigments in the medium. The pigments are typically copper phthalocyanine and iron oxides, and the gel is made up of water and biopolymers, such as xanthan gum and tragacanth gum, as well as some types of polyacrylate thickeners. The pigments are opaque, and gel pens are available in several bright and pastel colours, as well as opalescent, metallic, and glittery colours which show up clearly on dark paper. Many gel inks are water resistant, and are not washed away by water once the ink has dried. Fraud resistant gel ink is unaffected by solvents such as acetone, and resists cheque washing.

Ballpoint pens use a paste ink based on a dye solute in an alcohol solvent. Compared to ballpoint pens, gel pens:

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