Make a Green Gumball Black


  • A shoebox
  • A ruler
  • Scissors
  • Cellophane of several different colors
  • Tape
  • Several gumballs of different colors (white, red, blue, green, etc.)
  • A strong light source or a sunny day


  1. Cut a rectangular hole in the top of the shoe box 3 inches wide by 6 inches long.
  2. Cut out a rectangular piece of red cellophane about 8 inches wide by 14 inches long.
  3. Fold it in half twice to produce a filter of four layers with a size of about 4 inches by 7 inches.
  4. Tape the red cellophane filter to the inside of the shoe-box top so that it completely covers the rectangular hole.
  5. Cut a 1-inch round hole in one end of the shoe box.
  6. Put the gumballs inside the shoe box and put on the cover.
  7. Go out in the sunshine or shine a lamp through the cellophane.
  8. Look into the box through the round hole.
  9. See what colors the gumballs are.
  10. Repeat this experiment with different colors of cellophane.


A red object appears red because it reflects mostly red light back to your eyes. All the other colors of visible light are absorbed into the object. When you put a red filter over the hole in the shoe box, it filters out all the colors in the white light except for red. When this red light strikes the green gumball, it contains almost no green light for the gumball to reflect, so the gumball looks black. The same is true for the blue gumball. You can’t even tell the difference between green and blue. Almost all the light that strikes the red gumball gets reflected. Someone who looks in your red-filtered box containing a red and a blue gumball and tells you what colors they are will probably guess that they are white and black. This is because we see objects that reflect a lot of light as white and objects that absorb light as black.