The Science of Bubbles

People have enjoyed making and studying bubbles for hundreds of years. Although bubbles may look simple, they demonstrate important scientific ideas, including surface tension, air pressure, light, color, and geometry.

Bubble Solution

A bubble solution usually contains water and soap. Soap lowers the surface tension of water, allowing the water to stretch into a thin film instead of quickly breaking apart.

Adding glycerin or corn syrup (safter solution) can make bubbles stronger and help them last longer because these ingredients slow down evaporation.

Simple Bubble Solution Recipe

You will need:

• 6 cups of water
• 1 cup of liquid dish soap
• 1 tablespoon of glycerin or light corn syrup

Directions:

1. Pour the water into a clean container.
2. Slowly stir in the dish soap without creating too much foam.
3. Add the glycerin or corn syrup and stir gently.
4. Let the solution rest for several hours—or overnight—for better bubbles.

Bubble Wands

A bubble wand holds a thin film of bubble solution across an opening. When air moves through the film, the film stretches and forms a bubble.

Bubble wands can be made in many shapes and sizes. You can use pipe cleaners, wire, straws, cookie cutters, or other household objects. Surprisingly, the shape of the wand does not usually determine the shape of a free-floating bubble. A bubble released into the air becomes round.

Why Are Bubbles Round?

Bubbles are round because a sphere holds a given amount of air using the smallest possible surface area. Surface tension pulls the bubble’s soap film inward from every direction, creating a spherical shape.

Gravity and moving air can temporarily stretch or distort a bubble, but surface tension continues pulling it toward a round shape.

Bubble Hula Hoops

A hula hoop can be used as an extra-large bubble wand. Place the hoop in a shallow container of bubble solution, making sure the entire hoop is coated. Slowly lift it to create a giant bubble film.

With a large enough container, a person can stand inside the hoop while it is lifted around them. This creates a bubble wall surrounding the person!

This experiment shows that a bubble is not simply a single layer of soap. Its film consists of a thin layer of water held between two layers of soap molecules.

Can You Make a Square Bubble?

A free-floating bubble cannot remain square because surface tension pulls it into a sphere. However, you can use a cube-shaped frame to create soap films with straight edges and unusual geometric patterns.

When a cube-shaped frame is dipped into bubble solution, the films stretch between its edges. The films meet at angles that reduce their total surface area. If another bubble is placed inside the frame, it may appear cube-like while it remains connected to the surrounding films.

Once released from the frame, it becomes round again.

Why Do Bubbles Have Rainbow Colors?

White light contains many colors. When light strikes a bubble, some of it reflects from the outside of the soap film while some travels through the film and reflects from the inside.

The reflected light waves combine or cancel one another, producing changing bands of color. The colors shift as the bubble’s film moves and becomes thinner.

Just before a bubble pops, part of its surface may appear dark because the film has become extremely thin.

Try a Bubble Investigation

Experiment with bubbles by asking questions such as:

• Which bubble-solution recipe makes the longest-lasting bubbles?
• Do large and small wands produce different results?
• How does wind affect a bubble’s shape?
• What happens when different geometric frames are dipped into bubble solution?
• Do bubbles last longer in humid or dry air?

Make a prediction, test one change at a time, record your observations, and compare the results. That is how a fun bubble activity becomes a science experiment!

Bubble Safety

Bubble solution should not be swallowed. Keep it away from eyes, wipe up slippery spills, and ask an adult to help with large bubble experiments.  Remember that Universal Precautions for all science activities, means wearing eye protection.