Bath bomb ratios 2 parts baking soda to 1 part citric acid and 1 part corn starch (optional). Yes really that is it.
Now I wish I would have taken pictures of some of my bath bomb failures so I could show you what happens under different conditions.
Ingredients you can use to get your bath bomb to take a shape, otherwise all you have is a bath fizzy.
Most vegetable oils (excluding any that is a humectant like olive oil). Here is a pic of ones that turned out fairly well.
Most butters (in very warm weather be sure to use a hard one that has a high melting point) do not use coconut oil or babbasu oil in warm weather. Some people think these are butters as they harden in colder temps but they are really oils.
You can also use witch hazel, but never use anything with water in it, this is what sets the baking soda off to expand and fizz.
Be careful how much witch hazel or anything else you use, and also you might need to check the humidity as most bath bomb makers say when the humidity is above 70% it gets into the bath bomb mixture and sets the baking soda into action and leave you with a wet mess.
You don't have to make your bath bombs into a round ball shape using a plastic mold. You can also use any type of silicone mold. Actually silicone molds are easier to get your bath bombs out of. Make sure you give your bath bombs time to harden before you try to remove them or they will break apart in pieces.
Here is a picture of how I sell my bath bombs.