DIY Birthday Cake Bath Bomb – how to make cake slice bath bombs with soap icing and sprinkles.
5 from 1 vote

DIY Birthday Cake Bath Bomb

How to make birthday cake bath bombs topped with soap icing and sprinkles

Author Crystal Owens


  • 1 cup baking soda
  • ½ cup citric acid
  • ½ cup corn starch
  • 3 tbsp Epsom salt
  • 3 tsp coconut oil melted
  • Small spray bottle of Witch Hazel
  • 15 drops of essential oil
  • pink cosmetic grade pigment
  • sprinkles
  • 1/4 lb goat's milk soap base melted


  1. In a large bowl combine baking soda, citric acid, cornstarch, epsom salt and pigment.
  2. Pour in melted coconut oil and essential oil. Mix until well combined.
  3. Lightly spray witch hazel a few times until you can gather the mix in your fist and it holds its shape. If it easily falls apart then you might need 1-3 more sprays of witch hazel. Avoid spraying too much or your mix will start fizzing. You only need enough to slightly dampen the mix.
  4. fFirmly press the mix into your cake mold and allow them to set for a few hours or overnight, before removing.
  5. Melt soap and spoon over the cake bath bombs twice. Immediately add sprinkles. Let soap set for 10 minutes.

Recipe Notes

This recipe makes 2-3 bath bombs. Double the recipe in separate batches if you want to create a layered bath bomb.