Chromatography is a technique used to separate components which dissolve in the same solvent. Different components present in the ink have different solubility in the solvent. The component which is more soluble in the solvent travels more distance with the solvent. Likewise, the component with less solubility travels less distance with the solvent.

Paper chromatography is illustrated in the above figure. An ink spot is marked in a thin strip of filter paper. The bottom of the paper is immersed in a beaker containing water. As the water rises up, it takes along the different components present in the ink to different heights according to their solubility. As a result, colours (individual components of the ink) are seen along the height of the strip.

This way, the individual components are separated out using chromatography.