How to Blow Bubbles in a Bubble

Materials

For this activity, you will need:

• A bubble wand or bubble lasso or a wire coat hanger to make your own bubble wand
• 1/2 cup dishwashing liquid
• 1/2 cup sugar or 2 tablespoons of glycerine
• 4 cups warm water
• A shallow tray or container

How to blow bubbles in a bubble

Step 1: Build the wand

1. Unwrap the wire coathanger into one long piece of wire.
2. Bend one end of the wire into a circle, about 15cm in diameter.
3. Leave the rest of the coathanger straight to use as a handle.

Step 2: Make the bubble solution

1. Add the warm water, dishwashing liquid and sugar or glycerine to a large container.
2. Stir gently until the ingredients are fully mixed.
3. Make sure the container is wide enough to completely submerge the loop end of the wand.

Step 3: Create a large bubble

1. Dip your bubble wand into the bubble solution.
2. Make sure the entire loop is coated with a thin film of bubble solution.
3. Blow a large bubble using your bubble wand.
4. Keep the bubble attached to the bubble wand. If it starts floating away, gently put the wand loop underneath the bubble to catch it again.

Step 4: Blow bubbles inside the bubble

1. Hold the bubble on the wand close to your mouth.
2. Aim at the edge of the large bubble with your face pointing into the centre of the bubble.
3. Blow a few short, sharp breaths.
4. Watch as smaller bubbles become trapped inside the larger bubble.

You may need a few attempts to get the timing right. Short, sharp breaths work better than one long breath because they create separate small bubbles that can become enclosed by the larger bubble.

Step 5: Observe what happens

1. Count how many small bubbles you can trap inside the larger bubble.
2. Observe the shapes of the bubbles where they touch each other.
3. Watch what happens when the bubbles move, merge or pop.

How does it work?

This experiment demonstrates surface tension.

Water molecules naturally attract each other and form a thin surface layer. Dishwashing liquid reduces this attraction and allows the water to stretch into thin films.

Bubbles form when a thin layer of water becomes trapped between two layers of soap molecules.

A bubble naturally forms a sphere because:

• A sphere encloses the greatest volume with the smallest surface area.
• Surface tension pulls equally in all directions.
• The spherical shape requires the least amount of energy to maintain.

When air is blown against the edge of the large bubble, the soap film stretches and folds around the incoming air. If the film remains intact, it can reseal itself and trap smaller bubbles inside the larger bubble.

As long as the bubble film remains unbroken, the bubbles can exist together inside the larger bubble. The soap film continuously adjusts itself to maintain stable shapes while minimising its surface area.

This is why bubbles often appear to "heal" or reseal themselves rather than immediately popping.

Scientists study these same principles in materials science, engineering and mathematics, where similar structures are known as minimal surfaces.

Science fair project: Take it further

Once you have successfully made bubbles inside a bubble, investigate how different variables affect bubble formation.

• Compare different bubble solutions. Does adding more dishwashing liquid create stronger bubbles?
• Try blowing one, two, three or more bubbles inside the larger bubble. How many can you trap before the bubble pops?
• Experiment with different bubble wand sizes. Does a larger outer bubble make it easier to create bubbles inside?
• Observe the shapes formed when multiple bubbles touch. Do they remain spherical, or do flat surfaces appear where the bubbles meet?
• Compare gentle breaths with short, sharp breaths. Which technique produces the most stable bubbles?
• Create a table to record your observations. Which conditions produced the longest-lasting bubble? Which produced the greatest number of bubbles inside a bubble?
• Can you replicate a bubble-in-a-bubble in a cube shaped bubble?