Lava Lamp Instructions. Take one 16 oz water bottle. Pour out all but 1/4 of the water (4oz) and then add 10 oz vegetable oil to replace water. Add 10 drops food coloring. Watch where the food coloring goes and how the water and oil separate. Next, break up 2 alka seltzer tablets into 8 pieces and slowly drop one at a time into the bottle. Now you have your own little lava lamp. Thanks to the properties of water, oil and the carbon dioxide in the alka seltzer tablets, we are able to experience chemistry and math first hand. Our Widgetarians did the math and we enjoyed the results.