The secret is a simple technique called paper chromatography . It not only separates the pigments in ink, but shows capillary action at work.
Paper chromatography is a simple process and easy to do in class.
Tell students that they are going to make some surprising discoveries about the colors in ordinary markers. Based on the look of the color and what you know about mixing colors, predict which colors have gone into making the ink in your markers. Record your predictions. Using a different marker for each strip, draw a solid line across the bottom of the paper, about half an inch from the bottom edge. Write the brand or color name in pencil at the top of the strip and tape the top to a pencil.