Is green really green?
- a strip of paper towel or newspaper
- a green felt-tipped pen
- or a drop of green food dye
- a jar or glass with 1" (2.5 cm) of water
What to do:
Make a spot of color about 2" (5 cm) from one end of the strip of paper towel. Hang the strip in the jar so that the spot is above the water and the end of the strip is in the water. Let it stand for 15 to 20 minutes.
The green spot is gone-but above the original spot the paper has turned blue, and above that the paper is yellow.
Most dyes and inks are combinations of coloring substances which can be taken apart by adding water or alcohol. Water moves up the paper in the same way that sap rises in trees. As the water moves up, it dissolves the green spot and gradually moves the color up the strip of paper. But since the colors that make up green-blue and yellow-do not move at the same rate, they separate.