Kids, here we will separate the colors in ink and make a rainbow effect. You will need green and black water-soluble marker pens, a cone-shaped coffee filter (for Melitta coffeemakers), a saucer, and water. Regular coffee filters are too wrinkled and thin to work well. About 1/2 inch above the rounded edge of the flat, cone-shaped filter, make a thick, dark green line about one inch long parallel to the edge. Do the same with the black marker about one inch away from the green mark. You can do the same on the other side of the cone if you like. Pull out the filter so that you have a shape like an upside-down ice cream cone.

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

Fill the saucer with water, but only enough so that the water line is below your pen lines. Place the rounded edge of the cone in the water and let it sit for about 10 minutes. If there was too much water (above the ink lines) it will just wash off the ink. Let the water rise on the paper until it reaches about an inch from the tip of the cone. Then take it off the saucer and let it air dry.

A trail of color (purple, orange, pink, and yellow for an Expresso marker pen) should be separated from the black ink, while the green ink should make a trail of blue and yellow. This happens because black and green are combinations of many other colors. As the water rises on the paper, the ink dissolves in it. The colors separate and rise to different heights because of differences in the chemicals producing the color. The lighter-weight chemicals will move the fastest, which means that they will move with the water to the top of the paper.  

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
October 1992