Paper chromatography, separating coloured inks (vertical streaks). Chromatography is an analytical process that separates a compound into its constituent chemicals. Chromatography paper with the ink on it is dipped vertically in a solvent. Capillary action draws the solvent up through the paper, dissolving the ink. As the solvent travels up the paper it takes the various chemicals in the ink with it, separating them into a series of coloured bands. For example black coloured ink (far left) is composed of red, purple, blue and brown inks.