Ink has been in existence since ancient times, and its composition hasn’t changed much. In its simplest form, ink is a color suspended in a solvent. When the solvent evaporates, the color is left behind. Today’s inks are rarely simple, however. A variety additives are used to affect the thickness, drying time, permanence, appearance when dry, and other factors.
The color element of ink can be either a pigment or a dye. Pigments are are tiny, opaque bits of color suspended in a liquid. The pigment sits atop the paper or other printing material and binds with it, like paint on a wall. Pigment inks tend to be more expensive but are more commonly used because the color is more durable than with dye-based inks.
Dyes are colors that have an attraction to the printing material and want to combine with it, like dye coloring a piece of fabric or thread. Dye is dissolved in a liquid for application, and this liquid soaks into the printing material. This can make it a less desirable ink due to bleeding and blurring. To avoid this, the solvent used may dry quickly, or the drying speed is increased by air circulation or heat.