• Paper towels;
• Scissors;
• Bowl;
• Tape;
• Black pens (not ballpoint).

1. First, cut a paper towel into strips about one inch wide. Then draw a squiggly line across a strip of paper towel with one of your black pens, about an inch up from the bottom. Do the same for all the pens, and be sure to label the strips, so you know which strip goes with which pen.
2. Hang the strips over a bowl of water. The water should touch the very end of the paper towel, but not the ink.
3. Tape the paper towels in place and wait to see what happens. The water should creep up the paper towel strips and separate each ink mark into a cool dye pattern. This is called chromatography.
4. Now here's how to use this cool ZOOMsci to solve a mystery. Have a friend or a grown-up write a note on a paper towel using one of the pens, but make sure you don't know which pen is being used.
5. How will you find out which pen was used to write the note? You can compare the patterns from the pens to the pattern from the note to see which pen wrote the note.
6. To see the ink pattern in the note, cut a strip off the note. The strip needs to have ink on one end and no ink on the other end. Put the strip of paper towel in the water just like you did before.
7. Wait until the water creeps up the paper towel strips and separates the ink. Take the strip out of the water and compare it to the patterns you got before to solve the mystery of which pen wrote the note.

When the paper towel is dipped in water, some of the water sticks to the paper towel and gets it wet. There's a force between the water molecules and the molecules in the paper towel. That's called adhesion. The water also sticks to itself. That's called cohesion. Both of these sticky forces - adhesion and cohesion - cause the water to travel up the paper towel, moving against gravity.

When the water reaches the ink, it dissolves some of the dyes in the ink, and the dyes travel up the paper towel with the water. That's how you can see all the different colors that make up the ink. Try it out with different types of pens. Does a smelly marker make a different pattern than a non-smelly marker? What happens if you use a dry erase marker?