In a large mixing bowl, combine all dry ingredients (epsom salts, baking soda, corn starch and cream of tartar).
In a another small mixing bowl, combine the water, oil and food coloring, then combine the wet and dry ingredients. Your mixture should resemble wet sand at this stage in the process. If you're using a natural food coloring, you should be able to tell when it's well mixed once the coloring is even. Also, it should hold together when you squeeze some in your fist. If it doesn't hold together, add a few drops of water at a time until you reach the desired consistency.
Once it's the right consistency, tightly pack it down into your mold (the mini muffin pan). Allow the bath bombs to dry for 24 hours. I recommend not removing from the mold until the mixture is completely dry. However, depending on your mold shape, you may have success with early removal so you can reuse the molds more quickly. Cupcake and Flat shapes work great removing them from the mold early. More intricate designs do not.
Once you're ready, remove your DIY bath bombs from the mold and be sure they're completely dry before storing in an airtight container.
To use bath bombs, drop one in the bath tub and enjoy the soothing aromatherapy experience.
Print the recipe again: DIY Lavender Bath Bombs https://www.happy-mothering.com/how-to-make-your-own-diy-lavender-bath-bombs/