** Update**: For Week 6, Chemical Engineering, after the video was completed we removed seltzer tablets from packets because they may contain aspirin. You are welcome to use two seltzer tablets from home or these alternative ideas for the mixture--
Two tablespoons of baking soda added before the initial oil layer, then two tablespoons of vinegar along with the food coloring. This will create a similar CO2 reaction in place of the seltzer tablet.
Two tablespoons of baking soda and one tablespoon of lemon juice or one teaspoon of citric acid.
Baby oil is more transparent than cooking oil initially, but over time tends to create smaller globules that cluster together. It does smell nice, though.