All Colors Produce White
You will need: Card, pencil, scissors, water-color paints, brush,
string or thread, compass.
Set your compass at 1.5-inch radius and draw a circle on a piece of cardboard. Keep the compass at the same measurement and use it to mark off six equal divisions around the circle. Draw straight lines from these points at the outside directly to the center of the circle, as in Fig. 1.
Paint the various sections of the cardboard disc the colors marked. Ordinary watercolors from your paint box will serve quite well for this.
Allow time for the paint to dry and then make two small holes near the center of the disc, about 0.5-inch apart (see
X and Y).
Now pass a piece of thread about 3.5-feet in length through the two holes in the middle of the disc (Fig. 3), and tie the two ends together.
Hold the string by the loops at each end and get a friend to slide the cardboard disc along until it is midway between your hands. Now twirl the disc around until the string is tightly twisted and pull gently on the loops. You will soon find it quite easy to keep the disc spinning at high speed.
Once the card is spinning around really fast you will find that the bright colors you have painted on it merge together to produce white.