1. Mix the activated charcoal, citric acid and baking soda in a large bowl. You can separate this mixture into smaller bowls if you want to add in different natural food coloring or essential oils - mix them in after step 2.
2. Mix in the melted coconut oil thoroughly.
3. Mix in the essential oils and/or the natural food coloring if you are choosing to do this step.
4. The consistency of the mixture should be like wet sand. It should hold it's shape somewhat. If it does not, spritz with witch hazel and stir. Continue until it has a good consistency.
5. Fill half of the mold by gently packing in the mixture. Fill the second half of the mold higher, making a small dome. Press the two molds firmly together and wipe away any mixture from the sides. Make sure the molds are sealed. Keep it in the mold for 5 minutes.
6. Take the bath bomb out of the mold and have it dry for at least 24 hours.
7. Take a bath and enjoy!