Our favorite part of the summer showers that sometimes pop up out of nowhere is, obviously, the rainbow that follows. This Rainbow in a Jar experiment is the perfect way to keep kids learning while having fun. With simple household ingredients, children can build a real rainbow they can admire right in front of them, not off in the distant blue sky. The Rainbow in a Jar is a visually stunning STEAM activity that demonstrates how liquids of different densities behave. By stacking honey, corn syrup, dish soap, water, oil, and rubbing alcohol in a clear container, kids can see how heavier liquids sink while lighter ones rise. The result? A beautiful rainbow that rivals the value of a pot of gold.

Science in Disguise!

The science behind it is straightforward yet magical. You see, every liquid has its own density (how tightly its molecules are packed together). Honey, with very dense molecules, sinks to the bottom. Rubbing alcohol is much less dense, so it floats on top. Liquids like dish soap and oil layer in between with their own respective densities. Color each layer following the “ROYGBIV” spectrum for a more true-to-life rainbow look. Just remember to pour each layer very slowly so your rainbow doesn’t become a tie-dye swirl. Although beautiful, it’s not quite what we’re going for!

This experiment also helps kids understand the color spectrum, density, buoyancy, and molecule structure without needing safety goggles or a lab coat… unless, of course, your child really wants to wear a lab coat. In that case, we say go full scientist mode! Kids get a front-row seat to see how molecules affect the behavior of liquids. It’s science you can see (and occasionally taste… honey, anyone?)

It also puts the scientific method into action. From forming hypotheses to observing and recording results, this activity checks all the boxes of a real science investigation. Kids even get to practice motor skills like careful pouring, which is surprisingly similar to the real-life application of pouring juice and other drinks without making a mess. Good luck with that!

Build Your Rainbow Jar

Step 1: Gather Your Materials

What you’ll need:

• • A tall transparent container
  • A dropper
  • Water
  • Honey
  • Light corn syrup
  • Blue or green dish soap
  • Olive oil
  • Rubbing alcohol
  • Food coloring

Step 2: Add Honey

Pour about 2 centimeters of honey into the bottom of your jar. Try not to eat it. We know it’s tempting. This is your base and the densest liquid.

Step 3: Add Dyed Corn Syrup

In a separate bowl, mix a drop of red and a drop of blue food coloring into corn syrup to make purple. Carefully and slowly pour this on top of the honey. Let it settle. Now your rainbow jar is sporting its first two colors!

Step 4: Add Dish Soap

If your dish soap is already blue, you’re winning. If not, mix in some blue food coloring. Slowly pour it on top of the corn syrup layer. Go slow. Pretend you’re a scientist pouring liquid gold.

Step 5: Add Dyed Water

Mix yellow and blue food coloring into some water in a separate bowl. Slowly pour that green masterpiece down the side of the jar and notice how your rainbow is really shaping up.

Step 6: Add Olive Oil

Next up is our oil. No coloring needed here unless you’re feeling extra fancy. Pour it gently down the side. Fun fact: oil floats because it’s less dense than water, and also because it prefers to chill on top of things like it owns the place.

Step 7: Add Dyed Rubbing Alcohol

Mix red food coloring with rubbing alcohol in a separate bowl. Carefully add this as your final layer using a dropper. At this point, your jar should look like a rainbow that graduated from science school with honors.

Step 8: Observe the Rainbow!

You’ve done it! Look at those layers! They’re staying in place because of their different densities. It’s like a scientific masterpiece in a jar.

Take Your Rainbow Jar Experiment to the Next Level!

• • • Measure and Graph: Have students measure the thickness of each layer and create a simple bar graph.
      

• • • Swap the Liquids: Try substituting maple syrup for honey or vegetable oil for olive oil. See if and how it affects the rainbow. Warning: You may end up craving pancakes halfway through!

• • • Write About It: Before the project begins, encourage students to write down predictions about each layer and record what they observe. Their conclusion may be, “Science is sticky,” and honestly, we’ll take it.

• • • Drop Something In: Try dropping small objects, such as plastic beads, paper clips, or raisins, into the jar and watch what happens. Let students predict and test what will sink and what will float!

Chase the Rainbow with the Magic of Science!

This simple yet stunning experiment is exactly the kind of visual wow factor students love, and it’s a great example of how science can feel like magic when brought to life. Rainbow Jars are the perfect fusion of color, curiosity, and hands-on science, just like Mobile Ed’s Magic of Science program. If your students lit up during this tabletop activity, just imagine how exciting a full assembly packed with bubbling potions, magical magnets, amazing illusions, and other unforgettable demonstrations would be. Explore how you can bring the Magic of Science to your school by contacting us below!

Project inspired by: Playdough to Plato