With a paper towel, a black marker, and a cup of water, discover the secret colors hidden in black ink. This activity explores capillary action--how water moves up paper--and chromatography--how different elements of the ink are carried along at different rates, allowing you to see that black ink is actually made up of many different colors.

In this experiment, you're using a technique called chromatography.The name comes from the Greek words chroma and graph for "color writing." The technique was developed in 1901 by Russian botanist Mikhail Tsvet. He used it for separating the pigments that made up plant dyes. There are many different types of chromatography. In all of them, a gas or liquid (like the water in your experiment) flows through a stationary substance (like your coffee filter). Since different ingredients in a mixture are carried along at different rates, they end up in different places. By examining where all the ingredients ended up, scientists can figure out what was combined to make the mixture.