Mix together baking soda, arrowroot powder and citric acid.
When well incorporated, add essential oils, mixing thoroughly.
Alternate spraying mixture with Witch Hazel and mixing.
Continue spraying and mixing until mixture begins to stick together.
Spray ice cube trays, muffin cups or candy molds with Witch Hazel.(silicon molds like THIS work best)
Pack mixture tightly into molds, pressing down firmly.
At this point you can either turn packed bombs out onto a flat surface such as a cookie sheet to dry and cure, or leave them in the molds to dry. (24-72 hours)
Your bombs are ready to pack up and use when they are dry and hard.
Notes
Keep your fizzy bath bombs in an airtight container until you are ready to use them. Your bath bombs will keep indefinitely in very dry conditions, but moisture in the air will cause them to crumble over time.
Recipe by Primally Inspired at https://www.primallyinspired.com/fizzy-bath-bombs-recipe/