Walking Water Rainbow Science Experiment
Let’s make a walking water rainbow! There’s no better way for little scientists to learn about capillary action and color mixing than by making water walk (yes – walk!) in this colorful rainbow science experiment. This science experiment is a favorite of ours because it’s so easy to set up and the results are almost immediate.
Check out the simple step-by-step below and then gra b 30 more jaw-dropping (but easy prep!) science experiments kids will love from our shop!
Getting Ready
To prep, I gathered our supplies:
- 6 wide-mouth glasses or jars
- Paper towels (use the kind where you can select a size)
- Food dye or liquid water colors (red, yellow, and blue)
I grabbed the six small glasses first . We’ve had success using wide-mouth drinking cups and canning jars, too. Even though they all worked, just remember that bigger glasses will need more food coloring.
I ripped off six sheets of paper towel and folded each sheet in thirds, lengthwise.
We were using pretty small glasses, so I cut a few inches off the folded paper towel so it would fit in the glasses.
It’s a good idea to test your paper towel strip to make sure they fit properly in your glasses. They should be able to go from the bottom of one jar to the next without sticking up in the air too much. The paper towel on the left shows the just-right height. It’s important to set up this rainbow science experiment for success!
Making a Rainbow
This colorful rainbow science experiment is so simple and quick, it’s perfect for even the youngest little scientists. My 3 year old, Q, couldn’t wait to get started.
First, I had him line up the glasses and fill the first one with a good squirt of red watercolor , the third with yellow, and the fifth glass with blue. We left the other glasses empty.
Next, I helped Q add water to the glasses with color until the colored water almost reached the top.
We moved the glasses into a circle and added the paper towels . Starting with the red, we added one end of the paper towel and then put the other end in the empty glass next to it.
We continued around until the last paper towel was placed into the red glass.
We saw the color wick up the paper towel right away. This rainbow science experiment doesn’t take long to get going!
After another several minutes, the colored water had almost travelled the whole length of each paper towel.
Five minutes later, the water had traveled all the way up and then down the paper towel and was dripping into the empty glass.
The yellow and red water dripped into the empty cup to make orange! It made for a good lesson on color mixing.
After another five minutes, we could see the water level had dropped in the red, yellow, and blue glasses and rose in the once empty glasses as the water continued to travel from the more full glasses to the less full glasses.
We grabbed a snack and watched our beautiful rainbow science experiment during the next 20 minutes. The water continued to walk from the primary colored glasses to fill the secondary-colored glasses until all the jars were filled equally.
Not Working?
If you aren’t seeing much movement within a few minutes, it may be that you need to add more water to your colored water glasses. It really needs to be almost at the top for the water to walk quickly. So try topping off those glasses and seeing if that gets things moving.
If you see the water moving up the paper towel but it seems like it’s taking forever , it may be the type of paper towel you are using. You want a paper towel that will really hold a lot of water. We have used Bounty Select-a-Size and Target’s Up and Up Brand Select-a-Size with success.
It really is worth the extra effort of trying different cups and paper towels to get this activity to work. And once you have had success, don’t throw out those beautifully-colored paper towels or the colored water! We gently squeezed out our paper towels and let them dry in a heap on a baking sheet. We ended up with gorgeous tie-dyed looking paper towels to use for crafts and we used the leftover water as watercolors for painting with later.
The Science Behind It
This rainbow science experiment is as magic as the science behind it. The colored water travels up the paper towel by a process called capillary action . Capillary action is the ability of a liquid to flow upward, against gravity, in narrow spaces. This is the same thing that helps water climb from a plant’s roots to the leaves in the tree tops.
Paper towels, and all paper products, are made from fibers found in plants called cellulose . In this demonstration, the water flowed upwards through the tiny gaps between the cellulose fibers. The gaps in the towel acted like capillary tubes, pulling the water upwards.
The water is able to defy gravity as it travels upward due to the attractive forces between the water and the cellulose fibers.
The water molecules tend to cling to the cellulose fibers in the paper towel. This is called adhesion .
The water molecules are also attracted to each other and stick close together, a process called cohesion . So, as the water slowly moves up the tiny gaps in the paper towel fibers, the cohesive forces help to draw more water upwards.
At some point, the adhesive forces between the water and cellulose and the cohesive forces between the water molecules will be overcome by the gravitational forces on the weight of the water in the paper towel.
When that happens, the water will not travel up the paper towel anymore. That is why it helps to shorten the length that colored water has to travel by making sure your paper towel isn’t too tall and making sure you fill your colored liquid to the top of the glass.
Rainbow Science Activity Extensions
Turn this demonstration into a true experiment by varying the water level (volume) you start with and seeing how long it takes the water to reach the empty glass.
Or start with the same volume of colored water and change the brand, type (single vs double ply, quilted vs not) or length of paper towel to see how long it takes for the water to “walk” to the empty glass.
You could even use the same volume of water, same length and brand of paper towel but vary the height of the filled glass , by raising them up on books, to see how that affects the speed of the water as it “walks” to the empty glass.
Have you had enough fun with the paper towels? Try using other paper products to see how the type of paper effects the results. Try toilet paper, printer paper, newspaper or a page from a glossy magazine. What do you predict will happen?
Grab a Record Sheet
Help kids keep track of their results by grabbing our free record sheet! Then grab 30 more jaw-dropping (but easy prep!) science experiments kids will love from our shop!
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Rainbow Walking Water Science Experiment for Kids
This walking water science experiment is so much fun and super easy to do! My kids absolutely loved it! It even comes with free printable recording sheets for kids as young as preschool! Check out the video to see how easy this walking water experiment really is. This rainbow activity is perfect for spring science!
Walking Water Science Experiment
Ok, this might just be our favorite science experiment! The whole family (adults included) were completely mesmerized with process. We all couldn’t believe how quickly the water traveled up the paper towel and neat it was to watch the colors mix together.
We have wanted to try it out for a long time now and I am kicking myself for waiting so long. I don’t know why, but I thought it might be difficult to do or take a long time. I was way wrong. It was very easy and we started seeing results right away!
Related: Simple Spring Science and STEAM Activities
The walking water science experiment is great at any time of the year, but it is especially perfect for spring. I love doing rainbow activities in the spring, so this was a great addition to our rainbow theme activities.
If you are looking for simple science to do with the kids and something that will really WOW them, this is definitely one to try.
You only need a few simple supplies that you probably already have around the house.
Setting Up the Rainbow Science Experiment
Supplies Needed:
- Printable walking water recording sheets (button to download at the bottom of the post)
- Small plastic cups or glasses
- Paper towels (*read my tips below for picking the right ones)
- Food coloring in primary colors
* The pick-a-size paper towels are best because then you just use half sheets for each cup. If you only have full sheets, then cut them in half. I’ve also heard that more absorbent paper towels work better too. I buy the cheap store brand ones, and our water moved pretty quickly from cup to cup, so I am not sure how important that is. It may have went quicker with something more absorbent though.
1. Print out the recording sheets and make copies, if needed.
2. Place 7 cups in a row and pour water in the 1st, 3rd, 5th, and 7th cup. My cups were about 3/4 full. I have since heard that fuller is better.
3. Add 5 drops of red food coloring to the 1st cup and the 7th cup.
4. Add 5 drops of yellow food coloring to the 3rd cup.
5. Add 5 drops of blue food coloring to the 5th cup.
Doing the Walking Water Experiment
You want to try to use the same amount of food coloring in each cup. When I did this with my kids they did drop an extra one or two in since they can’t control it well, but I just added a drop or two more to the others to even it out.
6. Take a half sheet of paper towel and fold it in half lengthwise and in half again lengthwise.
7. Trim off some of the length so that there isn’t too much excess paper towel that will stick up in the air between each cup. This will make the water walk more quickly.
8. Place one half of a rolled paper towel in the 1st cup and place the other half in the cup next to it. Then another paper towel from 2nd cup and into the 3rd cup. This continues until you have placed the last paper towel that drapes over from the 6th cup to the 7th cup.
9. Stare at the cups and watch what starts happening. You should quickly be able to see the colored water begin to crawl up the paper towel.
10. Don’t forget to do the first part of the recording sheet. Students will predict what they think will happen.
This walking water experiment is AWESOME!
Keep checking back every couple of minutes. Soon you will be able to see that the water has crawled all the way up the paper towel and is beginning to walk back down into the empty cup next to it.
Since the cup on either side of an empty cup has colored water in it, the two colors begin to mix in the empty cup. So cool!
Keep coming back throughout the two hours or soon and observe what is happening.
Question to Ask
What do you think will happen to the water?
What is happening now?
Why do you think the colors are changing?
Why might the water be able to move up against gravity like that?
How this Science Experiment Works
The water moves up the paper towels through a process called capillary action. The paper towel is made from fibers and the water is able to travel through the gaps in the fibers. The gaps in the paper towel act like capillary tubes and pull the water upward. This is what helps water climb from a plant’s roots to the leaves at the top of the plant or tree.
The water is able to move upward against gravity because of the attractive forces between the water and the fibers in the paper towel.
I even removed one of the red cups and made a color wheel so I could introduce the kids to that as well.
I hope your kids have a great time with this super cool walking water science experiment!
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