Chromatography

Inks and dyes are generally made up of a mixture of different colors. Chromatography is a process that lets you separate ink into its individual colors.

Materials:

• Filter paper (paper towels or coffee filters will work too, but filter paper is best)
• Black marker or felt-tip pens, highlighters (non primary colors)
• Food coloring
• Several drinking glasses
• Several pencils

What to do:

1. Cut several strips of filter paper about a half-inch wide. Draw a big dot about a half-inch from the bottom of one of the strips with one of the markers or pens you want to test. Do the same thing on different strips for each pen you want to test.
2. Tape the strip to a pencil so that when the pencil rests across the cup the strip will hang down into the cup.
3. Pour water into each cup until it is just barely touching the bottom of the paper strip. Leave the strip hanging in the water until the color has traveled most of the way up the strip.

What's happening?

As the water creeps up the absorbent paper, it carries the color with it. Some components of the ink travel farther than others, causing the different colors to spread out so you can see them. How many colors do you see? Do the different brands of pens have different colors?

Many dyes are also made up of multiple colors. Try a chromatography experiment with some food coloring. Place a drop of food coloring in some water and hang a filter paper strip so it just barely touches the water. Does it separate into colors? Try mixing more than one color of food coloring and then see if you can separate them again with chromatography.

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