Inks and dyes are generally made up of a mixture of different colors. Chromatography is a process that lets you separate ink into its individual colors. Check out our video below to see it in action.
As the water creeps up the absorbent paper, it carries the color with it. Some components of the ink travel farther than others, causing the different colors to spread out so you can see them. How many colors do you see? Do the different brands of pens have different colors?
Many dyes are also made up of multiple colors. Try a chromatography experiment with some food coloring. Place a drop of food coloring in some water and hang a filter paper strip so it just barely touches the water. Does it separate into colors? Try mixing more than one color of food coloring and then see if you can separate them again with chromatography.
You can also do chromatography with permanent pens and markers; you'll just need to use a different solvent, since those inks don't dissolve in water. Try isopropyl (rubbing) alcohol or nail polish remover.
Get our Chromatography Experiment Kit for all the materials you need for fun chromatography projects.