Combine baking soda, citric acid, cornstarch and Epsom salt in a large bowl.
In a small cup, combine grapeseed oil, water and essential oils.
Slowly pour liquid into dry mixture and stir frequently. Use hands to thoroughly mix together
Scoop mixture into bath bomb molds and firmly press closed. Allow the bath bombs to dry overnight.
Remove from bath bomb mold.
Mix ½ tsp of black mica powder and a few drops of isopropyl alcohol in a small, disposable cup.
Paint face on using a small brush. Allow the mica powder to dry before storing in airtight container or plastic wrap.