The performer shows a large silk which is a solid color on both sides. He tosses a number of paper spots into the air, and as they flutter down the silk is swirled in the shower of spots. When the silk is now shown on both sides, it is Polka dotted, the paper spots having apparently fused on it.
The effect can be repeated in reverse, where you show the Polka dotted Silk, and as you shake it, the spots fall off to the floor, leaving the foulard a solid color.