A Science Experiment With Bath Bombs

A Science Experiment With Bath Bombs

What most people don't know about making bath bombs is that you are also doing chemistry at the same time. Bath bombs consists of various chemicals that combine together to create a relaxing and entertaining experience. This article is going to break down how to make bath bombs as well the science that is involved. 

What’s so intriguing about bath bombs? Bath bombs are so entertaining because they fizz in the bath and slowly turn the water different colors. They also smell amazing and make your skin so soft from the oils. You can make bath bombs in kid shapes using sand toys and, presto, taking a bath becomes fun again for people of ALL ages. They also make lovely gifts for family and friends.

Recipe: There are tons of recipes online so doing your research is crucial is finding the perfect recipe that works for you. Since we were taking the experimentation road we didn’t care too much if something went wrong as this taught us what not to do and what works best. We were having fun just trying things to see what would happen and if we can come up with something unique. Kids love the freedom of that as well. Some of the best lessons we learn are from our mistakes. I’ll break down the basic recipe we used and tell you some of the things we tried.


  • Citric acid 
  • Baking soda
  • Corn starch
  • Color (food coloring or liquid watercolor paint)
  • Oil (olive, vegetable, coconut & baby oil – or any of your choice)
  • Essential oils (for fragrance)

You’ll need regular cooking supplies like measuring cups, bowls, forks, etc.

Optional: We used epson salts and bath pearls as well and experimented with bubble bath (see how that experiment went below).

We used many different molds to create different shapes and sizes that we liked and that fit our personality. To get the kid shapes we used kinetic sand toy molds. 

Optional: We hid small toys like spinning tops and balls in the larger bath bombs and used cupcake liners to dry our finished bath bombs in.

Creating Your Own Bath Bombs

Mix Dry Ingredients: We made big batches of the dry mixture my making multiples of the basic recipe, and kept it in a large bowl to scoop out of. This is the basic mixture:

  • 1 cup citric acid
  • 1 cup baking soda
  • 1/2 cup corn starch

Mix together the wet ingredients: Mix 1/2 cup oil + drops of color + drops of essential oil in a separate bowl.

The type of oil, colors and essential oils are all your choice. This is where there is a lot of room for experimentation and learning for kids. It’s endless how many combinations you could make. For the oils we used vegetable, olive, baby and coconut. For the colors we used food coloring and liquid watercolor paint. For the essential oils we used peppermint, tangerine and Beautify (from Aveda). Repeat this process for every color and fragrance you want to make.

Add the wet mixture to 2 cups of the dry mixture and stir it together. If the mixture feels too dry and won’t stick together add some more oil – a little at a time. If it’s too wet add some more of your dry mixture. With a little experience you’ll get a good feel for the right consistency–something that sticks together pretty well just be squeezing it in your hand as you make a fist but breaks apart when you pinch it.

Put the mixed up bath bomb mixture in the molds. Once you have the mixture you want then add it to the molds you are using. Something as simple as a measuring cup as a mold works great. We also used sand toy from our kinetic sand for the kid shapes like starfish, alligators and cupcakes.

We experimented by adding layers, putting bath pearls at the bottom of the cup (which will later be the top), putting epson salts in the molds and hiding toys inside of the larger balls.  

Pack everything together as hard as you possibly can. Once you have packed everything in really tightly then tap on the mold and it should pop out into the palm of your hand – lay it out to dry either in a cupcake liner or on a paper towel. The oils will stain the paper as they dry.

Thing To Know Before You Begin

Oil – You can use any oil that you want. We experimented with vegetable oil, olive oil, baby oil and coconut oil. Try to keep it light. Some of the heavier cooking oils get, well, a bit oily in the tub when the bombs dissolve. I found that coconut oil was the nicest but let your kids play and see what they think. We learned – the fun way – to use oils instead of bubble bath to bind all of the ingredients together. We experimented to see if we could substitute the baby oil with bubble bath so our bath bombs would fizz and bubble in the tub. 

You can’t add the liquid soap into the mix or it starts the fun fizzy part a little sooner then you want it to! Maybe something like a dry foaming bath powder would work, but we couldn’t find any.

Color – We used regular food coloring and talked about making new colors from the basic primary colors. We didn’t experience any staining in the bathtub but of course be mindful of this before you add colors to your mixture.

We mixed yellow+red to get orange, red+blue to get purple and yellow+blue to get green. We also used some liquid watercolor paints that had glitter in them – that bath water was shiny and beautiful. We experimented with making new colors by mixing the colors together in the oil and by mixing the colors together in the dry mix (and then adding oil separately).

The image on the left is red and blue food coloring mixed together in the oil before adding it to the dry mix. The image on the right is red and blue food coloring mixed directly to the dry mix and then the oil added in separately. As you can see it made a difference, the colors never truly mixed together when we mixed them right into the dry mixture.

Fragrance – Use any kind of essential oils you want. We used peppermint, tangerine and Beautify from Aveda but you could order a fragrance of your choice or use things you already have.

Again, experiment with things like: what happens if we add the vanilla extract in our spice cabinet for the smell? Depending on the age of the kids you could really go nuts with experimenting with smells. Realize that if you use oils with a fragrance they will compete with your essential oil fragrances. 

Epson salt – we used an Epson salt that had a nice lavender fragrance. So for that batch we didn’t add any essential oils. We also noticed that partially through the mixture it started to get dry and we needed to add more oil. Our hypothesis is that the salts were absorbing some of the moisture and drying it up. When we added a little more oil it was fine.

What happens when you combine different oils, fragrances and colors to make your own bath bombs? The charts the kids could make of their observations, the pictures and the finished products would make this a great science experiment for school. 

I’d be lying if I said making your own bath bombs didn’t make a big mess and use tons of dishes, but then again, science can be messy. It all cleans up just fine in the end and it’s worth the mess.

Once the bath bombs are dry you can use them in your bath for your kids or to treat yourself to a nice relaxing bath. They are easy to make so when you run out, you can just make more or go to Bubbly Belle to see there amazing deals and bath bombs with ring!

Head over to Bubbly Belle to order some of our one-of-a-kind bath bombs.

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