3/4 inch schedule 40 PVC pipe (7 feet)

1/2 inch PVC pipe (2 feet)

Four 3/4 inch PVC elbows

One 4 inch PVC pipe (2 feet)

Flat PVC (4 inches x 20 inches)

PVC cement and primer

Epoxy

5 small screw eyes

String

Dawn dishwashing liquid

Glycerine

To form the trough : cut off the top portion of the 4 inch PVC pipe to form a trough. Save the cut off portion of the 4 inch pipe to make a dust cover. Cut the flat PVC in half. Cut 2 retangular pieces that are the height of the trough and at least 9 inches wide to form the sides of the trough. Sand the edges of all pieces. If a drain is desired, drill a hole into one endpiece before gluing it on.( A cork could be used to seal).Using expoxy, glue and seal the endpieces to the trough. Hold together with clamps. Cut flat sides on two of the elbows, (as shown in the illustration above). Cement and clamp an elbow to the inside of each endpiece.

To form the frame : cut the 3/4 pipe - one piece (22 inches); two pieces of equal length (24-30 inches). Cement the two remaining elbows to each end of the 22 inch piece to form the top of the frame. Insert the two pieces of equal length into the elbows of the top frame and the elbows in the trough. Drill aligning holes on both sides of the top frame and the wand.

To make the wand : cut the 1/2 pipe to fit inside the trough with a minimum of 5/8 inch between the pipe and inside of the frame. Seal the edges of the wand with 1/2 inch rounds cut out of the remaining flat PVC. Sand.

To make guide lines for the wand : cut 2 one inch pieces of the 1/2 inch pipe; cut each end of each piece to 45 degree angles (see illustration above). Cement each piece to bottom of trough (according to circled illustration). Screw the screw eyes into the top of the frame. Using a small piece of wire as a needle threader for the string, thread the string through the screw eyes in the top frame and attach to the holders in the trough.

To support the wand : screw in the remaining screw eyes, one to the center of the top frame and one to either edge of the wand. Again, thread the string through and assemble.

To form dust cover : cut slits into the cut off portion of the 4 inch pipe which align with the guide lines and slip over the trough (see illustration).

Entire structure may be painted black for effect.

Bubble Solution: 2/3 cup Dawn dishwashing liquid

1 tablespoon of glycerine

1 gallon of water

Aging the solution for at least a day significantly increases the strength of the soap film.

Improvements made by exploratorium staff and teachers

Please see original version of "Soap Film Painting" snack for this information.

Click here to get there.

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.