from Ultimate Book of Kid Concoctions
1/3 cup clear, mild liqid dish detergent
1 T cornstarch
1. Mix liquid dish detergent and cornstarch together in a small bowl until blended.
2. Pour the mixture in equal parts, into several sections of a plastic ice cube tray.
3. Add 1-2 drops of food coloring to each section of the tray and mix with a small spoon.