With three tumblers on the table, a measuring cup filled with water, paper towels, and food dye, I told my sons we were going to fill a cup with water without pouring a single drop in it.
"HOW?!?" they said.
"Let me show you!"
This experiment is simple. It did require patience, though. We prepared our cups in the afternoon and then watched throughout the evening and overnight.
How We Did It
Fill two identical drinking cups 2/3rds full of water. Put an empty cup of the same size between them. Squirt 8-10 drops of food coloring in the water-filled cups. We used yellow in one and blue in the other.
Now take a paper towel - we used a half sheet since we have the select-a-size rolls - and fold it the long way so the paper towel is about an inch wide. Do the same to another paper towel so you have two long flattened 1-inch wide rolls of paper towel. Fold them in the middle and put one end in the food dye, and the other in the empty cup.
Now observe what happens.
The paper towel absorbs the water and in doing so, the colored water is transferred from one cup to another. When the two primary colors, yellow and blue combine, they make green.
Even more fascinating is how the water level ends up perfectly even among all three cups. The water has been evenly distributed! It took about 36 hours for our water to "walk" from each of the end cups to the middle and even distribute between the three cups. Have patience!
This great experiment came from Coffee Cups and Crayons. Stop there to see other color combinations!