Material

Enamel paint like that used to paint model airplanes.
2 clear, flat, plastic squares(CD jewel boxes, cassette tape boxes etc.) at least 6 cm x 6 cm
clear tape 5 cm wide

Assembly

Put one strip of tape across each of the two plastic squares

To Do and Notice

Put a drop of paint onto the center of one of the pieces of tape.

Press the second plastic square down on top of the first one, put the two tape covered faces toward each other.

Squeeze the model airplane paint between the flat plastic plates to make a disk of color.

Notice that the paint spreads into a circular disk.

Pull the two plastic squares apart.

Try to pull them straight apart.

Notice the resulting pattern. This is a fractal pattern.

Pull the plates apart to make two copies of a fractal pattern.

When the plates are completely apart, set them aside to let the paint dry.

Optional, watch the paint dry. ;-)

What's Going On?

When a very viscous material, like paint, spreads into a less viscous material, like air, it spreads as a circular disk.

When a less viscous material like air spreads into a more viscous material like paint it spreads in a fractal pattern.

Fingers of air penetrate into the paint, these fingers then spawn smaller fingers at random, these spawn even smaller fingers. The resulting pattern is random yet contains fingers of air at many different scales. Such a random pattern which is similar over many different size scales is called a fractal pattern.

Etc.

You can also use thick yet liquid chocolate frosting to make the patterns. Since the patterns wash away you can make these patterns without using the clear tape. That is you can make them directly on the plastic plates.

A fractal pattern made with chocolate frosting.

Scientific Explorations with Paul Doherty

© 2005

8 May 2005

From an activity shown to me by Linda Shore.