Step 2: Choose your color(s). If the students wanted blue, green, yellow or red, they added 2 drops of food coloring. If they wanted to mix colors, they did 1 drop of each. Purple was a popular color with 1 drop of red and 1 drop of blue. I don’t recommend yellow because it is a very similar color to the vegetable oil.
Step 3: Fill the bottle with vegetable oil (1/3 of the bottle). I did this part because we didn’t have a good funnel to use. Even I made a bit of a mess!
Step 4: Place the cover on the bottle (tightly!).
The students then move the water bottle around as the bubbles move around. They are fascinated by the water and oil staying separate.