Paper chromatography. Chromatogram showing the composition of black ink. Chromatography is an analytical process that separates a compound into its constituent chemicals. Chromatography paper is dipped into a solvent with the ink painted on it. Capillary action draws the solvent through the paper and dissolves the ink. As the solvent travels through the paper it takes the various chemicals in the ink with it, separating them into a series of coloured bands.