In a large mixing bowl, combine the dry ingredients: Epsom salt, baking soda, citric acid.
Whisk everything together to ensure even distribution.In the mortar and pestle, or your choice of herb grinder, to grind the dried lavender and thyme into a fine powder. Once ground, add the powder to the other dry ingredients.
Stir the mixture until all of the ingredients are well combined. The consistency should resemble dry pancake mix. If you are including a few drops of carrier oil or essential oils, add those ingredienth of bath salts.
Test the fizz! Take a small amount of the bath salt mixture and drop it in a cup of hot water. If it fizzes vigorously, you’re good to go! If not, add a little more citric acid, a teaspoon at a time, and test again until you get the desired fizziness.
Once you’re happy with the consistency and fizz level, transfer the bath salts to the airtight containers. This recipe makes four 4-oz jars or two 8-oz jars worth of bath salts.