This experiment demonstrates some science you already know: that oil and water do not mix. Even if you try to really shake-up the bottle, the oil breaks up into small drops but will not mix with the water or the (water-based) food coloring. This will keep the oil distinct from the colored water, giving the lamp a nice effect. In addition, the Alka-Seltzer or Airborne tablet reacts with the water to make tiny bubbles of carbon dioxide gas. These bubbles attach themselves to the blobs of colored water and cause them to float to the surface. When the bubbles pop, the color blobs sink back to the bottom of the bottle.