Take about 1 tsp of baking soda and mix it with 10-15 drops of lavender essential oil and 10 drops of lemon essential oil.
Mix the baking soda and oils really well. This helps the oils blend with the other ingredients without causing a chemical reaction.
Add the rest of the baking soda, citric acid, and cornstarch to the oil-infused baking soda. I had fresh lavender on hand so I added it to these bombs for extra fragrance. Rose petals or other flower petals would also be nice.
Mix everything together really well until it's evenly combined.
Use a spray bottle to lightly spray the dry ingredients with water.
Spray just enough water so the dry mixture holds together well. It should hold together like wet sand when it is the right consistency. Be careful not to add too much water, as this will cause the mixture to fizz and dissolve prematurely.
Place the wet ingredients into silicone molds or form them into cubes or balls with your hands.
Remember not to fill the molds completely, as the bath bomb mixture will expand.
Allow the mixture to dry for about 30 minutes. You want it to harden enough to hold its shape but still be able to remove it from the mold.
Remove the bath bombs from the molds and place them on a piece of parchment paper.
Let them continue to dry for an additional hour.
Store your bath bombs in a glass jar or another dry place where they won't be exposed to moisture.
Avoid storing them in sandwich bags, as they will continue to produce gas and could burst the bag.
Use 2-3 cubes in your hot bath water at a time and enjoy the relaxing and skin-soothing benefits of your Lavender Lemon Bath Bombs.