Step 1. Cut a sheet of paper towel into the shape of a rainbow.
Step 2. Using the markers, draw the colors of the rainbow about an inch up on both ends of the paper towel rainbow. (Fig 1)
Step 3. Attach a paperclip to the paper towel top of the rainbow. Attach a piece of thread to the paperclip so now you have a way to hold the rainbow.
Step 4. Fill two small containers with water.
Step 5. Hold the ends of the rainbow slightly submerged in the water and watch your rainbow grow! (Fig 2)
Here is how it works! Paper towels are made up of plant fibers that absorb water very well. The water rises up through the space between the fibers, lifting the dye from the markers along with it.