Witches Brew Bath Bombs

Picture of Halloween bath bombsIf you’re looking for a way to keep your kids focused on learning this fall when all they can think about is Halloween and costumes, then we’ve got you covered! This easy, seven ingredient, bath bomb experiment will teach your children about the chemical reactions that happen when you combine elements with a negative and positive charge. A perfect way to bring out the mad scientist or witch in your child while brewing up some educational fun!

Science or fun … witch is it?

The fizziness of bath bombs occurs when the baking soda and citric acid in them create a chemical reaction when dropped into water. Baking soda, otherwise known as sodium bicarbonate, has the chemical formula NaHCO3. The sodium is positively charged (Na+) and the bicarbonate is negatively charged (HCO3-). When the baking soda dissolves in water, the positively charged sodium leaves behind the negatively charged bicarbonate. But what does this have to do with the citric acid?

Citric acid leaves behind a positively charged hydrogen (H+) when it dissolves in water. The positively charged hydrogen from the citric acid and the negatively charged bicarbonate from the baking soda form together to create a chemical reaction!

Want to learn more about chemical reactions? Try our other experiment on our blog: Create this Fun Pumpkin Volcano to Learn About Isotropic Reactions – My First Lab

You will need: 

  • 1 cup baking soda
  • 1/2 cup citric acid (you can find this in the baking aisle of a grocery store)\
  • 2 1/2 tbsp coconut oil (melted)
  • 2 tbsp water
  • 1/2 cup cornstarch
  • 1/2 cup fine sea salt

Optional Materials:

  • Whisk/spoon for stirring
  • Soap dye/food coloring
  • bath bomb molds (can substitute with cupcake tins)


  1. In a medium-sized bowl mix together the dry ingredients (baking soda, citric acid, cornstarch, and fine sea salt) until combined. Break up any chunks gently with a spoon.
  2. In a small bowl, combine the wet ingredients (coconut oil and water) together.
  3. Add the wet ingredients into the dry mixture, constantly stirring together with a whisk or spoon as you pour. Make sure you pour slowly to minimize the fizz from the chemical reaction.
  4. Once fully combined the mixture will hold together like wet sand. If your mixture is too dry, add a small amount of water.
  5. Divide up the mixture into separate bowls to create different colored bath bombs. Using either soap dye or food coloring, mix 2-5 drops into each bowl until the desired color is reached.
  6. Add the mixture to your mold. If using a bath bomb mold, overfill both sides with the mixture (do not pack down). Firmly press the two sides of the mold together until all of the excess mixture squeezes out.
  7. Allow the bath bomb to sit for a couple of moments before gently removing it from the mold.
  8. Let the bath bomb harden for 24 hours.
  9. Once the bath bomb is fully dry, drop it into warm water. If you want to feel like a real witch or mad scientist, drop the bath bomb into a beaker or mason jar and watch your kids light up with excitement as it fizzes and changes the color of the water!

My First Lab has been a leader in developing STEM equipment for the past 30 years. With products ranging from microscopes and bundles to prepared slides and accessories, we are sure to have any product that a junior investigator, hobbyist, or educational leader could need. Learn how to create hands-on experiments by browsing our blog or checking out our award-winning products.