Mix or sift together the baking soda, citric acid, and sea salt in a medium bowl. Break up any visible lumps with your fingers.

In a smaller, separate bowl stir the melted shea, coconut, or mango butter with the natural colorant, herbal powders, and/or essential oil (if using) together.

Drizzle the melted oils over the dry mixture, stirring with a whisk the entire time. As you work, break up any clumps with your fingers.

When the ingredients are completely incorporated, try squeezing a small handful of the mixture into a ball using your hands. If it crumbles, add it back into the main mixture and spray with 2 or 3 spritzes of witch hazel; give it another stir and try to make it into a ball again. Repeat this step until the mixture holds its shape without crumbling.

Fill the bath bomb molds with the mixture, adding extra (the molds should be overflowing) and lightly packing the molds as you work.

Press the molds together firmly without twisting. Use your fingers to remove any excess bath bomb mixture that spills out of the side.

Lightly tap each mold and carefully remove the top mold. Leave the bottom mold where it is, giving it another 15 minutes before removing it.*

Place the finished bath bombs on a soft towel and allow them to air dry for another 24 to 48 hours. Use within 4 to 6 months.