A young boy and young girl stir a mixture using wooden spoons

DIY Bath Bomb

STEM at Home: DIY Bath Bomb

What if you could use chemistry to create a bath-time treat that incorporated both fizzing bubbles and soothing salts? Well you can! This activity is easy and fun for all ages. Keep reading to learn how to make your own bath bombs.

Key concepts:

  • Chemistry
  • Chemical reaction
  • Acids
  • Bases

What you’ll need:

  1. 2 cups of baking soda
  2. 1 cup of citric acid 
  3. 1 cup of Epsom salts
  4. 1 teaspoons of water
  5. 1/4 teaspoon of essential oil or fragrance(optional)
  6. 1 tablespoon of oil
  7. food coloring (optional)
  8. bath bomb mold


  1. Combine the baking soda, citric acid, and Epsom salts together in a bowl. Mix well (Don’t forget to put on gloves)
  2. Combine the oil, color and water in a small container. Cover it with the lid and shake well.
  3. Slowly add (a few drops at a time) the liquid mixture to the dry mixture and stirring continuously and quickly.
  4. Pack and press down the mixture into molds and let rest. Come back to check them tomorrow.
  5. Carefully remove the mixture from the molds.  

Scientific Facts

  1. The borax acts as both a preservative and an emulsifier, stabilizing the acid and the base within the bath fizzies.
  2. Water is the catalyst that causes the reaction to occur. It dissolves the solids and allows the ions in the acid and the base to move and collide with each other, causing a chemical reaction.
  3. A catalyst is something added to a chemical mixture that speeds up the chemical reaction time. This reaction forms carbon dioxide, a gas, which rises to the surface of the bathwater in the form of bubbles.

* Put them in the refrigerator after that and let it sit overnight. This will help them firm and strong.

** Cornstarch will help them dissolve slowly. 

*** You can add flowers or herb into the mixture.

Questions you may ask:

  1. What happens if you put food coloring in the mixture?
  2. What happens when you add a drop of the wet mixture?
  3. Do the bath bombs take a different amount of time to dissolve depending on water temperature?