Ballpoint pens use viscous, oil-based inks. They’re made by dissolving dyes in a mixture of alcohols and fatty acids. Alcohols promote smooth ink flow, while fatty acids lubricate the tip of the pen. Because the ink is so thick, ballpoints work well on low-quality papers with little to no bleedthrough. However, they do require more pressure to write. This can be tiring over long periods of time, but some find these pens easier to control. Ballpoint inks are usually smudge resistant, quick drying, and waterproof.
Some ballpoints use hybrid or low-viscosity ink. This refers to an ink formulation that is enhanced with lubricants, making the ball at the tip rotate smoothly. They combine the best of the gel and ballpoint pen worlds. Hybrid ballpoints have the smooth flow and vibrance of a gel pen and the quick-drying ability and waterproofness of a ballpoint.
Writing anywhere, everyday carry
A gel pens ink consists of pigment suspended in a water-based gel. This particular formulation makes gel pens precise and vibrant. Very few other pens come in tip sizes as small as 0.28 mm--or as many colors. The smooth ink flow makes it much easier to write for long periods of time with less pressure, so you won’t get hand cramps as easily. However, gel pens tend to skip more than ballpoints or rollerballs. This is because their tips are not as evenly coated with the thinner, water-based ink. Gel pens also have longer dry times, so they can smudge if you’re not careful.
General note-taking, color-coded writing
A rollerball pen uses liquid ink consisting of dyes dissolved in water--similar to what’s commonly used with fountain pens. The ink flows freely in comparison to ballpoint and gel pens, so a rollerball requires less pressure to write. This helps to reduce hand strain and keeps you comfortable for long missives or note-taking sessions. However, using a liquid ink does mean that paper choice is important, as it will bleed through lower-quality papers. Rollerball pens often have more feedback (a tactile sensation where you “feel” the paper through the pen’s tip) due to the thinness of the ink. For those who prefer the smooth writing experience of other pens, broader tips and wetter writers deliver a more lubricated feel.