Soap-Bubble Shapes
Using chenille stems and drinking straws, you can make three-dimensional geometric frames: cubes, tetrahedrons, or shapes of your own design. When you dip these frames in a soap solution, the soap films that form on the frames are fascinating and colorful.
- Chenille stems, available at school supply, hobby, or party stores
- Plastic drinking or bar straws (bar straws, which have a smaller diameter than regular drinking straws, hold the chenille stems more tightly but are more expensive and sometimes harder to get; if you can’t find them at grocery or liquor stores, try restaurant or party supply stores)
- A small bucket or container for the bubble solution—large enough and deep enough so that bubble frames are entirely covered when they are dipped
- Bubble solution—use a commercial solution such as Wonder Bubbles, or make your own using the Exploratorium’s recipe: Gently mix 2/3 cup (160 mL) Dawn® dishwashing liquid and 1 tablespoon (15 mL) glycerin (available at most drugstores) with 1 gallon (3.8 L) of water
Bubble solution note: If you have trouble making good bubbles, try using distilled water instead of tap water. Letting the solution sit for at least a day before use significantly increases the lifetime of the bubbles.
- Mix the soap solution in the bucket. Make sure you have enough to fully cover the frames when they are dipped.
- Form frames using the drinking straws for the straight pieces. Try constructing cubes or tetrahedrons, or just let your imagination run wild.
- Connect two straws at a corner by inserting a doubled chenille stem into the end of each straw.
- In places where three straws meet, fold the chenille stems as shown in the diagram below (click to enlarge).
- Finally, attach a chenille stem handle to your frame.
Dip the frames into the soap solution and observe the fascinating geometrical shapes that form. Also notice the shimmering colors in the soap film.
As you lift your frame out of the solution, the soap film flows into a state of minimum energy. The soap film is in a state of minimum energy when it’s covering the least possible amount of surface area. The intricate shapes you see inside the frame represent the minimum area the soap film can cover. You may notice that a soap film will sometimes take on different shapes when you dip the frame into the solution again and again. That’s because there may be more than one way for the soap film to form a minimum surface area.
When light waves hit the soap film, they reflect and interfere with each other. This interference causes the shimmering colors you see.
White light is made of many different colors. When white light shines on the soap film, some light waves reflect from the front surface of the film and some reflect from the back surface of the film. When these two sets of reflected waves meet, they can add together, cancel each other out, or partially cancel, depending on the thickness of the film and the initial color of the light. When light waves of a particular color meet and cancel each other, that color is subtracted from white light. For example, if the red light waves cancel, then you see white light minus red light, which you perceive as blue-green light.
Look around for objects you can safely dip into the bubble mixture—from toys to kitchen implements—and you might be surprised at the soap-film shapes you can create.
