Galaxy Bath Bombs with a science lesson for kids

Galaxy Bath Bomb Recipe with Activated Charcoal

Learn how to make Galaxy Bath Bombs with activated charcoal that are out of this world! While also learning practical chemistry in this fantastic hands on science lesson for kids.

Keyword Galaxy Bath Bombs
Total Time 35 minutes


  • 2 cups baking soda
  • 1 cup citric acid
  • 1/2 cup cornstarch
  • 1/2 cup cream of tartar
  • 3 Tbsp coconut oil
  • 1 Tbsp polysorbate 80
  • 20 drops cedarwood essential oil
  • 1 - 2 Tbsp activated charcoal
  • 2-3 drops colouring (purple, blue and pink)


  1. In a large mixing bowl, add the baking soda, citric acid, cornstarch, and the cream of tartar.

  2. In a small bowl mix coconut oil, cedarwood essential oil (or the essential oil of your choice) and the polysorbate 80. Add to the large bowl and mix.

  3. Use your hands to break down any lumps and make sure everything is really mixed in there. This is a great sensory moment for the kids. The mixture is perfect when the mixture sticks together when you press into your hands and feels like wet sand.

  4. Separate the mixture evenly between four bowls.

  5. To the first bowl, add the black cosmetic glitter and 1 tablespoon of activated charcoal. Mix ingredients together thoroughly. If your mix is not black enough, add 1/2 tablespoon more of activated charcoal and mix. Repeat until you have a nice black.

  6. To bowls 2, 3 and 4 add the purple, blue and pink coloring to one bowl each. Start with just a couple of drops, mix well. Then add a few more. Remember, moisture is our enemy when making bath bombs, so go slow. Add your choice of glitters to each of the three bowls. Mix each bowl well.

  7. Take a bath bomb mold and fill each side with the different colors of the mixture, alternating between the four colors, in any pattern you like. Press both sides together, using a twisting/grinding motion to get rid of any excess mixture. Gently tap each side and carefully remove the bomb.

  8. Leave molds to harden for at least 24 to 48 hours (depending on your climate). Once hard, store in an airtight container, away from any moisture, until ready to use.