Soap Film Painting
A soap film becomes an ever-changing work of art.
Under the influence of gravity, a thin film of soap constantly -changes thickness, creating an everchanging array of colors.

(1 hour or less)

Drill two small holes 11 inches (28 cm) apart in the 24 inch (60 m) overhead member and the plastic pipe. Drill a single hole at the center of the overhead member. Drill a second set of holes 1 inch (2.5 cm) closer to the center of the pipe. All the holes should be large enough to let the fishing line be inserted through them, and to let the line travel through them freely when necessary.

Epoxy the lower anchor into the plastic tray and fix the screw eyes into the wood 11 inches (28 cm) apart.

Assemble the base and upright supports and nail the overhead member into position (see the diagram and the photo).

Tie lengths of fishing line to the screw eyes. Thread the pipe on, then thread the line through the outside holes in the overhead member and knot them in place. Make the lines as taut as possible to allow the pipe to travel freely up and down.

Run another piece of fishing line down through one of the inside holes in the pipe and up through the other hole. Tie a slip knot to form a noose. Run the free end of the line up through the hole in the center of the overhead member to act as a lifting cord (see diagram).

Fill the plastic tray with bubble solution until at least the entire lower half of the pipe is submerged.

(15 minutes or more)

Pull the string and raise the bar out of the soapy water to make a soap film.

Notice the changing colors reflected by the film. The colored patterns in the vertical soap film are most easily seen by standing with your back to a white surface and viewing the soap film against a black background.

Shake the frame back and forth repeatedly. Notice the pattern of waves on the film.

Stand a few feet away from the film and blow on it gently. The film stretches out into a bulge when you blow and returns to its original flat shape when you stop.

A soap film is a soapy water sandwich, with two outside layers of soap molecules forming boundaries around a layer of soapy water. The thickness of the soap film changes as the water drains down the inside of the film. When light strikes the front surface of the bubble film, some of the light is reflected (about 4%). The remainder of the wave is transmitted through to the rear surface. At the rear surface of the soap film, more of the light is reflected back to your eyes. The light reflecting from the front of the film meets up with the light reflecting from the back of the film, and the waves combine.

The beautiful colors you see on the soap film are due to interference patterns, created when light reflects off the two surfaces of the thin soap film. Interference patterns are created when two reflected waves line up in phase or out of phase.

If two waves line up in phase, with crests together and troughs together, we say that the waves are interfering constructively. When two waves line up out of phase, crest to trough, we say that the waves are interfering destructively.

White light can be considered a mixture of three additive primary colors: red, green and blue. If the thickness of the soap film is just right to cause the destructive interference of one of the additive primaries, you will perceive a mixture of the two remaining colors:

white - red = blue + green = cyan (bluish green)
white - green = red + blue = magenta (reddish blue)
white - blue = red + green = yellow

Therefore, everywhere you see yellow, the film is just the right thickness to destructively remove the blue light waves. Where you see cyan, the red light has been destructively removed. And where you see magenta, the green light has been destructively removed.