Ever wonder why some colors dissolve in water and others don't? Take a look and see what's up.
Why do some black inks separate into many colors on a wet coffee filter?
Most nonpermanent markers use inks that are made of colored pigments and water. When you write on the coffee filter, the ink solution dries. Once you add a drop of water, the dried pigments dissolve and as the water travels through the paper, it carries the different particles that make up the colored pigment. Different-colored pigments are carried along at different rates; some travel farther and faster than others. How fast each pigment travels depends on the size of the pigment molecule and on how strongly the pigment is attracted to the paper. Since the water carries the different pigments at different rates, the black ink separates to reveal the colors that were mixed to make it. The technique used to separate colors this way is called chromatography. The name comes from the Greek words chroma and graph for "color writing." The technique was developed in 1910 by Russian botanist Mikhail Tsvet. He used it for separating the pigments that made up plant dyes.
Why does mixing many colors of ink make black?
Ink and paint get their colors by absorbing some of the colors in white light and reflecting others. Green ink looks green because it reflects the green part of white light and absorbs all the other colors. Red ink looks red because it reflects red light and absorbs all the other colors. When you mix green, red, blue, and yellow ink, each ink that you add absorbs more light. That leaves less light to reflect to your eye. Since the mixture absorbs light of many colors and reflects very little, you end up with black.
You can do this with other stuff in your kitchen like candy. Why not see just what colors you're really eating when chomping on your halloween candy?