ALLEGRA BOVERMAN/Staff photo. Gloucester Daily Times. Gloucester: Kaci Orlando, 7, makes waves inside a water bottle by tilting it, after creating a lava lamp-like effect with water, oil, food coloring and Alka Seltzer tablets, during the monthly science workshop at the Sawyer Free Library on Tuesday. More tablets can be added to create more fizz to the mixture on an ongoing basis to keep up the effect. Children were learning about the density of liquids and solids.