What You Need
- food coloring
- tall clear glass
- another cup or glass
- Fill the tall glass almost to the top with room-temperature water. Warm water is ok, too.
- Pour a little oil into the other glass. (1-2 tablespoons)
- Add a couple of drops of food coloring. I used one drop of blue and one drop of red, but you can use any colors.
- Briefly stir the oil and food coloring mixture with a fork. You want to break up the food coloring drops into smaller drops, but not thoroughly mix the liquid.
- Pour the oil and coloring mixture into the tall glass.
- Now watch! The food coloring will slowly sink in the glass, with each droplet expanding outward as it falls, resembling fireworks falling into water.
Food coloring dissolves in water, but not in oil. When you stir the food coloring in the oil, you are breaking up the coloring droplets (though drops that come into contact with each other will merge... blue + red = purple). Oil is less dense than water, so the oil will float at the top of the glass. As the colored drops sink to the bottom of the oil, they mix with the water. The color diffuses outward as the heavier colored drop falls to the bottom.