Did you know that bath bombs – the super popular bathtime toy – work because of a chemical reaction? ​​We’re mixing some kitchen staples together that will create an explosion of colorful carbon dioxide (CO2) bubbles when the bath bomb hits the water!

Ready to make this project at home or in your classroom? Watch the video for an overview, gather the materials listed at the right, and follow the instructions below!

Required Materials

  • 1 cup baking soda
  • 1/2 cup citric acid
  • 1/2 cup corn starch
  • baby oil (any skin safe oil will work)
  • food coloring
  • bath bomb mold (cupcake tin, plastic egg, etc.)

Step-By-Step Instructions

Step 1

Combine baking soda, citric acid and cornstarch together in a bowl and mix well.

Step 2

Add food coloring as desired.

Step 3

Add one teaspoon of baby oil, just enough to moisten the mixture so that the powder sticks together. Keep adding the oil until the mixture holds its shape when pinched (it will still look powdery).

Step 4

Pre-prep the mold with baby oil and corn starch. Place a very small amount of oil into the mold and dust the corn starch over it – similar to preparing a pan for baking. 

Step 5

Scoop the mixture into a mold to form a shape.  Let the shapes dry overnight.

Step 6

After 24 hours have passed, the bath bomb is ready to use! Watch the chemical reaction occur when the bath bomb mixture made of corn starch, citric acid, and baking soda combines with water to create some thing new – carbon dioxide gas, aka the bubbles!