This is a fun project for all ages. We began by talking about the artist Jackson Pollock. I showed the class this poster from the library and asked what they could "see" within his painting. There were many amusing answers and this led us to a short discussion of abstract art.
Next, I handed out a blank sheet of white paper, a marble, and a tray to each student. (There are a stack of trays in the art supply closet that are perfect for this project...and don't forget the tub full of t-shirt smocks to keep the paint off their clothes). I squeezed 4-5 large drops of different colored tempera paint on each sheet of paper. The students carefully rolled their marbles back and forth across the paint by tipping their trays from side to side.
The results are really neat. This is a picture from when we did this project at home last year. If you mount the finished project on black cardstock it looks really professional!