In a large container, mix together 32 ounces of baking soda and 16 ounces of citric acid. To get rid of clumps, you can push the powder through a sifter or break them up with your fingers. Citric acid has a tendency to take off nail polish, so wear gloves to protect your manicure. 

Mix together 2 tablespoons each of red rose petals, marigold petals, and cornflower petals in a small bowl.

Add 1 ounce of chamomile extract, 0.3 ounces of polysorbate 80, and 9 mL of lavender 40/42 essential oil to the powder. Use your hands to thoroughly mix in the wet ingredients.

Test the consistency of the bath bomb mixture. The perfect consistency for molding is similar to wet sand and holds its shape when squeezed. If it’s too dry, use one hand to spritz the mixture with witch hazel and one to mix. Continue spritzing until the mixture holds its shape when squeezed.

Place a small pinch of the petal mixture into one half of the bath bomb mold. Cover the petals with a bit of the powder and pack it in firmly.

Fill the 2 halves of the molds, gently pressing the bath bomb mixture in each so they hold their shape. Mound a little extra in the center of each half of the molds. Wipe away any powder in the seams of the mold, match the eyelets, and press together. Make sure to direct pressure to the edges of the mold rather than the center. 

Allow the bath bombs to fully dry for 2-4 hours, or up to overnight. When you’re ready to use, unmold the bath bomb, drop it into a hot bath, and enjoy!