What you'll need to make bath bombs 2 Tbsp. baking soda 1 Tbsp. of citric acid (or 1/2 tablespoon cream of tartar) 1 Tbsp. of cornstarch 1 Tbsp. Epsom salts 1/4 tsp. Coconut oil 3/4 teaspoon liquid* brew a very strong, very concentrated tea a drop or two of food coloring Dump the dry ingredients (baking soda, acid, cornstarch, and salts) into a bowl and whisk together to remove lumps.