Fireworks Indoors? Explore surface tension with a milky fireworks show!

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Here in the United States, we’re getting ready to celebrate the Fourth of July. That means it’s time to get patriotic with our STEM experiments!

Magic Milk shows how dish soap separates the fat and water molecules within milk using food coloring as the visual component. Milk is comprised of fats, water, and other substances. By adding dish soap, we affect the surface tension of the milk with “water-loving” and “water-hating” parts, which separate the fats and water. The food coloring shows this reaction!

Let’s get to the fireworks!

How to make the Magic Milk Fireworks experiment

Supplies you will need

For this experiment, you’ll need:

Supplies needed for the Magic Milk Fireworks experiment

Before you start

It is important to use whole milk for this experiment because it has the highest fat. Since the Magic Milk experiment is all about how the dish soap separates water and fats in milk, you will want to use the highest fat milk possible.


Here is how to do this experiment with your child:

Step 1: Pour the milk into a shallow, wide bowl

Pour enough milk into the shallow, wide bowl that it covers the bottom plus another 1/2” or so.

Pour the milk into a shallow, wide bowl

Step 2: Pour some dish soap into a smaller bowl

Into a separate, smaller bowl, pour a small amount of dish soap. You don’t need much; this is just enough to cover a Q-tip for the experiment.

Pour a small amount of dish soap into a separate bowl

Step 3: Add drops of food coloring to the milk bowl

If you want to keep it patriotic, only add blue and red food coloring to the bowl with milk in it. Experiment with how much and where you place the colors for the best effect!

Add food coloring to the milk as desired

Step 4: Dip the Q-tip into the soap and then into the milk for explosions of color

Cover the tip of a Q-tip in the dish soap and touch the food coloring spots on the milk. You don’t have to dunk the Q-tip. Only a slight touch will produce the best results!

Reapply the dish soap on the Q-tip as needed. You can also continue adding colors to the milk or experiment by adding a drop of soap to the milk and a drop or two of food coloring on top of the soap.

Dip the Q-tip into the dish soap, ensuring you cover a good portion of the Q-tip
Gently touch the Q-tip to the colors in the milk

The STEM behind the Magic Milk Fireworks experiment

This experiment teaches:

  • Surface tension
  • Chemical reactions
  • Creativity
  • Independence Day

How it works

Milk is made up of fat, protein, water, vitamins, and minerals.

When we add dish soap to our milk with a Q-Tip, we are separating those fats and water inside the milk. This is why we need milk with all of its fat content. The separation is happening at such a small level that there’s no way we could see it, so we have to add food coloring to show it happening.

Touching a Q-Tip with dish soap on it to the milk separates the fats and water really quickly, and we see that in how quickly the colors move away from our Q-Tip!

Surface tension

Milk has a thin film on its surface that acts like a stretchy sheet. That stretchy sheet is called surface tension.

Surface tension is like a tight skin on top of the milk. It happens because the water molecules like to cling to each other, but instead of having molecules all around like inside of the liquid, the molecules at the surface only have molecules next to and below it.

Those molecules at the surface therefore pull inwards, forming a thin sheet at the surface. That’s why water droplets are round and some bugs can walk on water!

Dish soap disrupts this film, making the colors spread wildly.

Chemical reactions

While it might look like magic, the soap and milk are undergoing a chemical reaction.

The soap molecules are attracted to the fat in the milk, causing the fat to clump together. That’s why it is important to use milk with the highest fat content possible.

This movement pushes the food coloring around, creating the swirling effect that we see.


Experimenting with colors in this fashion exercises creativity to create some beautiful art with our milk experiment!

Use this opportunity to talk about color mixing, designs, and other creative topics.

Independence Day

Of course, we can also use this opportunity to talk about the United States’ Independence Day to get a little history in our STEM lesson!

For example, do you know why the colors red, white, and blue were chosen for the American flag? Red symbolizes hardiness and valor, white symbolizes purity and innocence, and blue represents vigilance, perseverance and justice.

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