rainbow cup experiment

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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Science Fun

Walking Rainbow Color Science Experiment

In this fun and easy science experiment, we’re going to explore and investigate colors by creating a walking rainbow. This classic experiment is awesome, bright colored, and packed with amazing science!

• Several colors of food coloring
• 3 clear plastic cups or glasses of the same size
• Paper towels

Instructions:

• Select the colors you would like to incorporate into the Walking Rainbow Water experiment.
• Fill up a plastic cup or glass with a few drops of food coloring. Fill the rest of the cup about halfway full with room temperature water.
• Now replicate this step but use a new unique color. You need to have an extra empty glass of the exact same size for the water to walk into.
• Cut a paper towel in half and after that fold it into quarters lengthwise.
• Put one end of the paper towel into the colored water and another end into the empty jar. Now use the other halved and folded piece of paper towel by placing one end in the other cup of colored water and its opposite end into the empty cup.
• Wait for the science to take place! You should soon see both colored waters climbing the paper towels and joining in the empty cup.

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How it Works:

Because of capillary action, the water flows or “walks” up and over the paper towels right into the empty cup. The empty cup fills up with water until the water levels of every one of the cups are equal. The original colors will mix creating a new color. 

Make This A Science Project:

Try different colors. Try expanding the experiment with more cups or jars of colored water and additional empty vessels to see how far you can make the water walk. Try different types of paper. Try substituting water with vinegar. Try and adding salt to the water. Try very cold water. 

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Rainbow Walking Water Science Experiment

• rainbow skittles science experiement
• rainbow flower science
• rainbow baking soda science experiment

MORE SCIENCE EXPERIMENTS FOR KIDS

Supplies for the walking water experiment

• 6 small transparent jars or cups
• Paper towels / kitchen roll
• Liquid watercolour / food colouring

Walking Water Science Experiment 

STEP 1: Get your supplies ready

Step 2: prepare the jars with coloured water.

STEP 3: Place the jars in a circle

STEP 4: Predict what will happen

STEP 5: Add paper towels  

STEP 6: Watch the coloured water walk along the paper towels to create a rainbow!

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All Science Fair Projects

1000 science fair projects with complete instructions, walking rainbow experiment.

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Grow a Rainbow Science Experiment

Grow a rainbow with your kids! This simple experiment is so easy and fun! You just need markers, a paper towel and two cups of water! This experiment is quick to setup and just takes a few minutes to finish!

The great thing about this experiment is young kids can do almost all of it on their own! Our kids completed it several times! As always, make sure you supervise the kids and be sure to ask questions about the science experiment !

Supplies Needed:

• Two Clear Cups
• Marker (Washable Markers)
• Paper Towel

Video of Grow a Rainbow Experiment

Grow a rainbow instructions.

• Take a paper towel and fold it in half so it absorbs the water better. 
• You will then want your kids to measure the paper towel and cut it at around 7 inches. You don’t want it too long, as the colors might not connect in the middle if it is. Our cups were so short that the paper towel could have been a bit shorter and the colors would have met in the middle even better.

• You will want to use the markers to fill in about 6 or 7 rectangles on both sides of the paper towel. They should extend out about an inch and a half. Use the colors of the rainbow or close to it: Red, orange, yellow, green, blue, indigo, violet.

• After that, pour water into the 2 cups. You will want the cups to be about 1/2 to 3/4 full. This will depend on how tall your cups are.
• You will now gently put one end of the paper towel in one cup and the other end in the second cup – making a bridge between the two cups. Try to make sure the paper towel doesn’t fall too far into the water. If it does pull it out slightly or separate the cups a little more. 
• Now you just wait and watch the fun! The colors should connect in 5 – 10 minutes!

Additional Tips

• Do not place the paper towels too far into the water as the color will dissolve into the water and not travel as high.
• The more marker dye you use, the easier it will be for the colors to travel up and meet.
• Make sure you use a really washable marker. The more washable they are, the better the colors will travel up the napkins.
• Use an absorbent paper towel.

The kids had a blast with this science activity! They enjoyed trying different colors and amounts of marker. They would try to color in the sides of the paper towel with extra marker dye to make the colors connect even faster.

This activity definitely kept them busy and having fun. And it was easy to set up and quick to clean up too!

How does this simple science activity work?

In this rainbow experiment, capillary action is the reason the water moves up the paper towels.

Capillary action occurs because water is sticky since water molecules like to stay together (cohesion). And thanks to adhesion, water sticks to other substances and will move along their walls. This allows the water to move up the paper towels!

This same action is how water moves up into plants from the roots! It’s also why paper towels and pool towels are great at absorbing water!

Extend the Fun

Your kids can extend the fun by trying different colors, different paper towel lengths and different amounts of marker. Our kids tried to use a lot of marker to get the colors to grow faster!

They absolutely loved this science experiment! It was one of the easiest we have tried and they had a blast trying lots of variations!

Using markers, water and paper towels is a great way to show capillary action at work and amaze your kids!

Check out the Rainbow Walking Water and Color Changing Flower experiments below for more fun experiments showing capillary action.

More Fun Rainbow Science Experiments

The rainbow walking water is our most popular science activity! This one uses capillary action too!

You can use the colors of the rainbow with this color changing flower experiment ! This is another experiment using capillary action.

This  rainbow skittles experiment  is a fun rainbow activity for the kids!

Looking for more capillary experiments. This Celery Food Coloring Experiment is fantastic! – via Little Bins for Little Hands