Step 1. In a large mixing bowl, combine dry ingredients: Citric Acid, Baking Soda, Corn Starch, and Epsom Salt. Use a wire whisk to mix the ingredients evenly, breaking up any clumps of powder.
Step 2. Slowly drizzle grapeseed oil over the dry ingredients, mixing everything until it is evenly combined. (You can either use the essential oils individually in three separated batches of mixture, or blend them to create one or more fragrances which can be used on one or more of the batches of mixture.)
Step 3. Once the mixture is thoroughly blended, test a bit of the mixture in the palm of your hand - It should stick together like wet sand. If it crumbles or appears dry, fill the spray bottle with water or rubbing alcohol and add 20-40 pumps of the spritz to your mixture each time. Stir continually.
** Tip: Using the right amount of water is the key to making beautiful bath bombs. You want to use the least amount of water, adding only a bit at a time, so that your mixture sticks together but does not become active. (Here at Urban Kangaroo, which is based in Southern California, we use approximately one-half bottle (about 2 tbsp) of water, and on humid days, we use no more than 1.5 tbsp of water.) **
Step 4. At this stage, dried rose petals can optionally be added for color and decoration. Test a bit of the mixture in the palm of your hand again.
Step 5. Once the mixture is well-blended, you will be ready to add your mixture to your molds. Each mold should be filled to the point at which the tops of molds are “mounded over.” Place one mold in each hand and push the two mounds together firmly. Brush away excess parts of your mixture from the edge of your molds.
At this point, your mixture should firmly stick together. If your two mounds are not adhering, check whether the edges of your molds are clean and free of mixture. You can try adding more mixture to the molds, and then repeating step 3 (i.e. repeating the molding process).
Step 6. Gently tap the top of the molds and carefully remove your finished bath bombs from the mixture. Place bath bombs on a clean surface (a paper towel is a good option) and allow them to dry overnight. Repeat this process for the remainder of the bath bombs. Let the bath bombs harden and dry for 12-24 hours, until they are no longer moist to the touch. When the bath bombs are ready to package, place them in the bags provided, and tie the bags with the gold twist ties. Apply the labels onto the bags.