I had so much fun with this experiment the other day! You really need to try it – it just blew me away! I saw it on Pinterest and I was intrigued and wanted to do this with my kids – C is 7, S is 5. I stopped by the dollar store and got paper towels and plastic cups and I was ready to go (I already had food coloring and liquid water colors). I tried it out while they were both in school so to make sure it would work – things don’t always seem to turn out as expected when doing Pinterest projects.
It is such an easy experiment to set up – set up 7 plastic cups in a row (or you can do 6 in a circle – but I found it harder for the kids to make observations when they were in a circle). Fill the first cup with red water, followed by an empty cup, yellow water, empty cup, blue water, empty cup, and finally a red water cup. Fold paper towels lengthwise into fourths so they are long skinny strips. Fold the skinny strips in half to make a V shape. Then connect the cups with paper towels placing the end of the paper towel strips into adjacent cups (red cup to empty cup; empty cup to yellow cup, etc). There are instant changes – the colored water starts traveling up the paper towel pretty quickly.
I was amazed – my kids were amazed. My son (5) immediately made the prediction the colored water was going to go into the empty cups and mix. It was a great activity for little ones to introduce science practices – observations and predictions, and introduce or review color mixing. As I did the experiment, I realized that there was complicated science going on behind the scenes and realized this would be a great experiment for older kids to learn about the water molecule and its properties: adhesion, cohesion, and capillary action. So I made it into a lab I could use in my classroom and adapted it to be used at lower elementary, upper elementary, and middle school. We let the experiment sit on our counter for 3 days to see the changes.
I set up the experiment with food coloring and liquid water colors to see what worked the best. Both worked well, but I had new liquid water colors so I ended up using those with my kids. You don’t need a lot of color, the color on the paper towels becomes darker over time. I way overdid the color in the pic above (bottom right). The colors were too dark to see the colors mix in the cups.
Once we were done experimenting, we used the liquid water colors to make a resist painting. The kids drew on their paper with white crayon and then painted over it. The area with crayon did not absorb the color. It tied in with the experiment and was a fun way to use the leftovers. We sprinkled some salt on the paintings too since that it always fun to see the changes with sale.