Start out by gathering your supplies. You'll really want to pre-measure and have everything ready to go before you start. Once you begin, the whole process goes quickly and you don't want to have to scramble for an ingredient. Here's what you'll need:
1 cup baking soda
1/4 cup cream of tartar
1/2 cup cornstarch
1/2 cup Epsom salt
2 tsp essential oil
2 1/2 tbsp coconut oil
1-2 drops food coloring (optional)
1 tbsp water (as needed)
Combine the Dry Ingredients
In a glass bowl, combine baking soda, cream of tartar, cornstarch, and Epsom salt. Mix together thoroughly with a whisk. You really need to make sure that everything is combined properly. For this step, you don't want to use a plastic bowl. Some experts think that the plastic can mess with the wet ingredients. Fair warning: bath bombs are really finicky. This means you can't just toss ingredients into a bowl, you need to be as precise as possible.
Combine Wet Ingredients
In a smaller separate bowl, combine the coconut oil, food coloring, and essential oils. Whisk them all together. You might notice after mixing that the food coloring isn't completely blended into the oils, if that's the case, don't worry just do your best.
Combine Wet with Dry Ingredients
Drizzle the wet ingredients into the dry ingredients slowly while mixing constantly. You don't want to dump the wet ingredients in too quickly, as that could start the fizzy chemical reaction. Mix thoroughly until there are no big lumps and the mixture is similar to damp sand. If you grab it with your hand and squeeze the mix should hold its shape.
Press Into Molds
Now this might be a little controversial, but making round bath bombs can be really challenging. We know some people might debate this, but we've made a lot of bath bombs and it's hard to make a version that doesn't crumble. So instead, we've found it easier to use a silicone mold. Not only are the bath bombs easier to remove once they're more stable and dried out, but you can make multiple at the same time. When you're working with these molds, you're going to want to press them firmly into the mold. Really push down hard so you're packing the bath bomb mixture into each mold—this will help keep them together.
Remove from Molds
Then we like to pop the mold into the fridge for a few hours to help set them. Once they seem pretty dried out and solid, remove the bath bombs from the mold and let them sit overnight to finish drying out.
Once they're done, they're yours to use! Or you can wrap them up in some pretty tissue paper and gift them to friends and family.