One of the most difficult things is to find Citric Acid at a reasonable price. I buy mine in bulk from New Directions Aromatics. They have a Canadian location that provides wonderful customer service combined with fantastic pricing on products and shipping.
To make cupcake bath bombs you will need:
6 Cupcake Liners of your Choice
A small muffin tin
Spray bottle with Water
3/4 cup Citric Acid
1 cup Baking Soda
Sprinkles for decoration
3 TablespoonsWhite SLS Free Soap Base
Combine the Citric Acid, Baking Soda and Cornstarch in a small bowl with a whisk. Add in your essential oil of choice. Depending on the oil it will vary for how many drops. 15-30 drops to make them strong enough to smell when they fizz later in the bath. Whisk well. Spray 5 spritzes at a time on the bath bomb mixture. Whisk and repeat the water spritzes. Checking for the right texture by squeezing the powder in your fist. If it holds together then stop adding the water. A spritzer is a MUST. Do not just add a teaspoon of water to the mix or it will fizz up in one spot and not do anything to the rest. Too much water will create a bath bomb that overflows overnight to look like a volcano.
Place your cupcake liners into your muffin tins. 1/4 Cup at a time pour in the mixture and compress down with the back part of the measuring cup. Once all liners are filled and compressed set aside with a cover over them so the scent doesn't dissipate. Allow to sit for 6-24 hours.
Once they are hard you can add the decorations. Melt 3 tablespoons of white soap base in a measuring cup and once liquefied, use a small spoon to pour soap over the top. Working quickly, sprinkle the tops with flowers or candy decorations of your choice. Wrap immediately with cellophane and tie with a bow.