Science of Bubbles

What you need:
•    Dish soap
•    Glycerin (available at some drug stores or order online)
•    Water
•    Wire, string, straws, modeling clay, toothpicks (to make bubble wands)

Try This:
1.    First, you need to make the bubble solution. Here’s the recipe:
•    ½ cup dish detergent
•    4 ½ cups water
•    4 Tablespoons glycerin
2.    Make a funny shaped bubble wand using the wire, or string and straws.
3.    Try to blow some bubbles. Can you make a funny shaped bubble?
4.    Use the toothpicks and clay to make three dimensional bubble wands. Try the shape of a cube or a pyramid.

Bubble Wands

5.    Dip the wand in the bubble solution and look at it BEFORE you blow. What shapes does it make?
6.    Experiment with different bubble wands and make some observations.
7.    You can also experiment with different recipes of bubble solution. See what it takes to make a better bubble!

What’s going on?
The shape of the bubbles is determined by surface tension. This is what holds the bubble together. It’s also what allows you to fill a cup with water over the brim without spilling. The bubble always tries to make the shape with the minimal surface area. In the free air, this is always a sphere. With the 3-D wands you may get some funny shapes. The edges have been set and the bubble fills in the least possible area inside the shape, which isn’t always what you would expect.

You may also notice that the bubbles are pretty colors. The bubble is acting somewhat like a prism to break apart the colors of the rainbow. The colors in the bubble are formed when light diffracts as it hits the bubble. This just means that the light is interfering with itself. Imagine you throw two pebbles in a pond and see their ripples interact. The bigger waves or high points are constructive interference; the small waves or low points are destructive interference. The light waves behave in the same way, which creates patterns on the bubbles’ surface and allows us to see the colors.

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This page updated on September 18, 2007