Gel pen

Detail of the tip of a gel pen

A gel pen uses ink in which pigment is suspended in a water-based gel.^[1] 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).

Inks

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.

Gel pens

Comparisons

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

• Create a bolder, more opaque line
• Smudge more, due to ink being wetter
• Have occasional skips, due to the ball being less evenly coated with ink
• Use more ink, leading to more frequent refills or replacements
• Are more likely to leak ink when the stopper fluid drains out
• May be able to write on smooth, non-absorbent materials

Fountain pens and liquid-ink rollerball pens use a dye solute in a water-based solvent. Compared to these pens, gel pens:

• Are less prone to bleed through to the other side of a piece of paper
• Create finer, more controlled lines
• Can create white or brightly coloured opaque lines on dark surfaces
• May be able to write on smooth materials

Paint markers use an oil-based paint/ink that is very opaque and overlays all other colours beneath it. Compared to paint markers, gel pens:

• Are smaller, with finer tips
• Have no odour and do not require shaking to mix pigment with solvent

India ink (based on carbon black pigment) is perhaps the ink closest to gel ink in opacity, although it is usually made with an alcohol and shellac-based binder:

Another trait of gel ink is that it resists an analytical method commonly used to assess the potential age of ink for forensic purposes. The United States Secret Service has maintained the International Ink Library for many decades. Because manufacturers change their ink formulas slightly from year to year, thin-layer chromatography (TLC) can be used on ink from traditional pens to trace the manufacturer and date of manufacture of most inks. The pigments in gel ink do not dissolve, and therefore cannot be analyzed with TLC.^[2]

See also

• List of pen types, brands and companies

References