On the left side of every tin I added about two tablespoons of baking soda to each. I just eyed it so some may have more than others. Then on the right I added about the same amount of vinegar.
I then dyed the vinegar. I used wilton gels hence the toothpicks :)
Once it's all mixed I just give her a tray and let her have at it. When she is ready for another she normally just asks.
This is super easy to set up and recreate over and over again. Bubbles, color, fizzing, fun!!!