What is a basic proportions of baking soda and citric acid necessary to make the fizzing reaction happen?
2 parts Baking Soda to 1 part Citric Acid Use less baking soda to create a harder bath bomb that dries faster and is less crumbly. You can play a bit with the ratio to find what best suits you. You can use as little as 2 cups or as much as 4 cups of baking soda to 1 cup citric and still get good fizzing action.
