Whisk together the baking soda, citric acid, Kaolin white clay, dead sea salts and cornstarch in a large bowl. Make sure they are well combined.

Stir the the coconut oil into the dry ingredients until combined then stir in the Polysorbate 80.

Add in scented oil and mix well. You can use any skin safe scented oils you like. You may need to use your hands to break down any lumps and make sure everything is mixed in. The mixture is perfect when it holds together when you press it into your hands and feels like wet sand.

Mix in the purple colorant. Start with 1-2 drops of color and mix it in. If you want a darker color, add 1-2 more drops and repeat until you get the color you want.

Using an ice cream scoop or spoon, fill each cavity of the muffin tin or mold. Press down firmly. Add more until the cavity is filled to the top.

Allow the cupcake bath bombs to dry a minimum of 24 hours. If your climate is wet or cold, allow an additional 24 hours. The rule of thumb is that when they are nice and hard to the touch, they are ready for the frosting! 

To remove from a metal muffin tin, gently run a knife around the outer edge and release. If using a silicone mold, gently pop each bomb free.

Add the whipped soap base, scented oil and glycerin to a mixing bowl. Mix on low speed until fluffy, or about 1 minute.

Melt soap base in microwave safe bowl in 30-second intervals, stirring after each until melted.  You can also melt the soap base on low heat in a small pot on the stove top. Allow to cool for about a minute after being melted.

Mix together the melted soap base and cornstarch. Mix on high speed for 1 minute or until the mixture forms peaks, similar to making a meringue.  If frosting is not stiff enough, add a bit more cornstarch and mix in. Repeat until the mixture is nice and firm.

Divide the whipped soap into 3 small mixing bowls. Add pink color to one bowl, yellow to another and light green to the last bowl. Start with 1-2 drops of color. If you want a darker color, add 1-2 more drops and repeat until you get the desired intensity in the colors.

Fill the piping bags by adding one of each color frosting to each of the 3 piping bags. Once the bags are full of the whipped soap, hold the bags together so all sides of the tips meet.  Put it all together by add frosting tip and the coupler.

Holding all three bags tightly in your dominant hand, frost cupcake bombs as you would an edible cupcake. Add a few sprinkles if you like. 

Allow the cupcakes to sit for 2-3 days. The frosting will harden enough that you can easily remove it from the cupcake and use the soap once you have enjoyed your soak in the tub with your bath bomb!