Color Separation (Chromatography)

You know candy is colored with artificial dye.  But did you know that many candies contain several kinds of dye?  To see the different dyes for yourself, try this.

M&M chromatography.  Brown has separated into the most colors (right).

What you need:

• A rectangle of coffee filter paper
• Dyed candy such as M&Ms, Skittles, or Reese's Pieces
• A glass filled with a half-inch of water
• A pencil

What to do:

1. Place drops of water on a flat surface, such as a plate, a cookie sheet, or tinfoil.
   
2. Place candy on water and let color dissolve.
3. Crease the coffee filter paper vertically (to help it stand up). 
4. Dab or paint a drop of candy-colored water onto the paper, an inch from the bottom.  If you're testing several colors, label each with pencil.
   
5. Stand the paper up in the glass of water, with the water level below the color splotch.  (If the paper doesn't stand, check here for tips on folding or clipping the paper in place.)
   
6. Watch the water seep up to the top edge of the paper.

What's happening:

When water seeps up the filter paper, it separates the different colors so you can see them.  M&M brown works especially well--the different dyes separate out into a rainbow. 

You can try this experiment with anything that contains dye, including juice, markers, or ballpoint pen (that’s why it’s better to mark your labels with pencil). 

Explanation based on author's interview with Walter Bowyer, chemistry professor at Hobart and William Smith Colleges