Gather all the supplies and ingredients, including 2 bowls, a whisk, measuring spoons, the bath bomb molds, baking soda, citric acid, Epsom salts, olive oil, water, essential oil, and food coloring.
Measure out 1 cup of baking soda, 1/2 of citric acid, and 1/2 cup of Epsom salts, and combine all of these dry ingredients in one bowl.
Whisk together all of the dry ingredients thoroughly.
Measure out 1 tsp. of water and 3 tsp. of olive oil, and combine these in the other bowl.
Add in 2 tsp. of essential oil and the as much food coloring as desired.
Whisk together all of the wet ingredients thoroughly.
Add the wet mixture in with the dry mixture, whisking and adding a little as you go. Once the entire wet mixture is added, make sure it has all been whisked thoroughly.
Firmly pack the mixture into the molds and close them.
Leave the bath bombs into the mold for an hour or overnight, so they can dry.
Carefully pop the bath bomb out of the mold.