rainbow in a glass experiment explanation

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Rainbow in a Jar Science Experiment

Want to make your own rainbow? In this simple science experiment, kids can build their own rainbow in a jar while exploring density, mass, and volume.

Watch our demonstration video, gather your supplies, and print out our detailed instructions to get started. An easy to understand explanation of how it works is included below.

rainbow in a glass experiment explanation

JUMP TO SECTION: Instructions | Video Tutorial | How it Works

Supplies Needed

Tall Glass Jar
Food Coloring: Red, Blue and Green
1/4 cup Honey
1/4 cup Blue Dish Soap
1/4 cup Water
1/4 cup Olive Oil
1/4 cup Rubbing Alcohol
Jars for mixing and pouring
Teaspoons for mixing

Rainbow in a Jar Science Lab Kit – Only $5

Use our easy Rainbow in a Jar Science Lab Kit to grab your students’ attention without the stress of planning!

It’s everything you need to make science easy for teachers and fun for students — using inexpensive materials you probably already have in your storage closet!

Rainbow in a Jar Science ExperimentInstructions

Step 1 – Add one drop of red food coloring and one drop of blue food coloring to 1/4 cup of honey and stir until combined. This creates a purple color liquid. Pour the purple liquid carefully into the tall jar.

Step 2 – Next add about 1/4 cup of blue dish soap to the tall jar.

Step 3 – Add a few drops of green food coloring to 1/4 cup of water and mix until combined. Then, carefully pour the green liquid into the tall jar. Tip: When pouring in the green liquid, tilt the jar so the liquid runs down the side of the jar slowly.

Step 4 – Wait a few moments and then slowly pour 1/4 cup of olive oil into the jar. Again, be very careful when pouring in the liquid. Make sure to tilt the jar and pour very slowly so the colors don’t mix.

Step 5 – Add a few drops of red food coloring to 1/4 cup of rubbing alcohol and mix until combined. Then, carefully pour the red liquid into the tall jar. Tip: I can’t stress enough how important it is to tilt the jar and pour slow. Otherwise, the colors will mix together and you won’t get a distinct rainbow.

Do you know why you were able to make the liquids form the rainbow in a jar? Find out the answer in the how does this experiment work section below.

Video Tutorial

How Does the Science Experiment Work

Density is the reason that this experiment works! Density is a measure of how much mass (or “stuff”) there is in a given volume. Density is a ratio of mass to volume and can be found by dividing an object’s mass by its volume (D=m/v).

Based on this equation, if the mass of something increases but the volume stays constant, then the density increases. Also, if mass decreases but the volume stays constant, then the density decreases. Density is all about how tightly packed the matter making up the material is in a given volume. Lighter liquids (like olive oil and rubbing alcohol) are less dense than heavier liquids (like honey and dish soap) because they have less matter in a given volume. Because olive oil and rubbing alcohol are less dense, they will float on top of liquids like water, dish soap, and honey. Liquids with a lower density will always float on top of liquids with a higher density.

All liquids have their own unique density. Water has a density of 1 g/mL (g/cm3). Objects will float in water if their density is less than 1 g/mL. Objects will sink in water if their density is greater than 1 g/mL.

I hope you enjoyed the experiment. Here are some printable instructions:

Instructions

Add one drop of red food coloring and one drop of blue food coloring to 1/4 cup of honey and stir until combined. This is create a purple color liquid. Pour the purple liquid carefully into the tall jar.
Next add about 1/4 cup of blue dish soap to the tall jar.
Then add a few drops of green food coloring to 1/4 cup of water and mix until combined. Then carefully pour the green liquid into the tall jar. Tip: When pouring in the green liquid, tilt the jar so the liquid runs down the side of the jar slowly.
Wait a few moments and then slowly pour 1/4 cup of olive oil into the jar. Tip: Again, be very careful when pouring in the liquid. Make sure to tilt the jar and pour very slowly so the colors don’t mix.
Add a few drops of red food coloring to 1/4 cup of rubbing alcohol and mix until combined. Then carefully pour the red liquid into the tall jar. Tip: I can’t stress enough how important it is to tilt the jar and pour slow. Otherwise the colors will mix together and you won’t get a distinct rainbow.

Reader Interactions

October 15, 2017 at 3:22 pm

It was cool. Was it density

October 30, 2017 at 11:33 am

Hi it was Cooooolllllll….. It was because of the density

June 12, 2018 at 10:22 am

my kids enjoyed this presentation. They are doing it for a stem project

March 25, 2019 at 3:41 pm

How long did this project take to make and how long did it last until the colors started to mix? Also, what would be the guiding question of an experiment like this?

March 2, 2023 at 11:46 am

1.This experiment took around 20 minutes to put together. 2. It lasts for as long as you need if nobody touches it. 3. A leading question to this experiment could be ” Will all of the ingredients mix while i am pouring?”

I hope this helped:)

January 23, 2020 at 12:41 pm

its amazing my students loved it!

March 2, 2023 at 11:40 am

I did this exact project for the science fair this year and I won 2nd place. I made a full board about destiny and I made a question saying ” If I do not tip the jar or if i pour too fast, will the colors mix? The answer is yes! The colors did mix whenever I didn’t tip the jar and the rubbing alcohol sank down and mixed with the green and then since the extra liquid was in the green it mixed with the blue dish soap and began to be a big bubbly mess! 🙂

June 12, 2023 at 10:15 am

Can you put a top on the jar, shake the jar, mixing the liquids, will the liquids separate after sitting for hours or days?