How To Make Avengers Bath Bombs & The Science Behind The Fizz

Bringing together Avengers and Bath Bombs into one DIY project was a dream come true for my superhero, bath loving kid! These Avengers Bath Bombs are incredibly easy to make, and they provided some really interesting and exciting chemistry lessons. These are so cute, they even make amazing gifts!

How To Make Avengers Bath Bombs and The Science Behind Why Bath Bombs Fizz

DIY Avengers Bath Bombs for kids with a chemistry lesson that will have kids asking for more!

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Avengers Bath Bombs Recipe

​Yields: 8-12 (depending on size of your molds)

Silicone muffin mold
1 cup Baking soda (also known as bicarbonate soda)
1/2 cup Citric acid
1 Tablespoon almond oil (substitute for olive or coconut oil for a nut free version)
1-2 Tablespoons water
Avengers Icing Decorations
90% or higher isopropyl alcohol in a small spray bottle
Optional – your favorite soap scent (I used marshmallow)



Bath Bomb Making Safety Note

I highly recommend using safety goggles, gloves and a face mask when mixing up bath bombs, especially if the kids are helping you. Citric acid can be irritating and you definitely do not want to get it in your eyes. With my heart condition, I also find it is always best to be safe and protect my airways when working with anything that can become airborne. Always use common sense and protect yourself. And of course, kids should always do this project under responsible adult supervision.

How To Make Avengers Bath Bombs

1. Add the baking soda, critic acid, soap scent (optional) and almond oil to a mixing bowl (use glass or metal) and whisk together.

Bath Bomb recipe ingredients laid out for making Avengers Bath Bombs

2. Add the water, one tablespoon at a time and stir to distribute. You want the mixture to feel like damp sand and it should clump together when you squeeze it in your hand. Go slow, or you could end up with lots of fizzing!

Adding bath bomb ingredients to a bowl and whisking them together.

3. If after adding two tablespoons you feel like the mixture isn’t wet enough, spritz it with 4-5 sprays of isopropyl alcohol and stir. Be cautious using isopropyl alcohol spray. This step should be done by a responsible adult or tween/teen under the supervision of an adult. You don’t want to inhale the isopropyl alcohol.

4. Transfer the bath bomb mixture into each mold, filling each cavity 3/4 of the way. Use your fingers to press the mixture down tightly.

Bath bomb mixture in molds ready to have Avengers decals added

5. Spritz the top of each bath bomb 2 times with isopropyl alcohol to dampen and firmly insert an Avengers icing decoration into each bath bomb.

Finished Avengers Bath Bombs being left to dry

6. Allow them to air dry for 24 hours.

7. Gently pop out each bath bomb from its mold and store in an airtight container.

8. Add to a warm bath and enjoy!!

Note: You can store these for up to 2 weeks, but it is important to keep the moisture away from them. Ensure they are in an airtight container and if you live in a very humid place, consider wrapping them in plastic to keep the moisture away.

Final Avengers Bath Bombs close up

DIY Bath Bomb Trouble Shooting

There are a few things that can cause issues while making bath bombs. Here are some tips to overcome those struggles.

Premature Fizzing Of The Bath Bombs

If you live somewhere with high humidity or it is a rainy day, the bath bombs will take moisture from the air and start reacting. Reduce the amount of liquid used in the making of the bath bombs and, if at all possible, chose a drier day to make them. Also, ensure they are stored in an air tight container.

Bath Bombs Puff Up While Drying

The puffing up is also a result of too much moisture, so reduce the amount of water to reduce puffing up while they are setting.

Crumbly Bath Bombs

On the other hand, if your bath bombs are too crumbly and not holding their shape, you will need to add a little bit more water.


Final Avengers Bath Bombs ready for the bath to explore some chemistry lessons

Why Do Bath Bombs Fizz?

A Chemistry Lesson for Kids

There are a variety of different recipes for making bath bombs, but the key ingredients are baking soda and citric acid. From our previous chemistry studies we know that baking soda is a base and citric acid is obviously an acid. When a base and an acid are combined, we get a reaction. Just like in our Naked Eggs ExperimentDino Eggs and Bottle Rockets.

With bath bombs we need one more ingredient to make the reaction happen, and that’s water. In our previous experiments we often use vinegar as the acid. Vinegar already has water in it, so there was no need to add water too. When baking soda and citric acid are mixed then placed in water, they undergo a chemical reaction. The bubbles that make the bath water so fizzy are carbon dioxide gas.

Next Steps – Bath Bomb Science Experiment

So after the success of our Avengers Bath Bombs and the chemistry lessons we learned, our next step is to explore more of bath bomb science and see how we can manipulate the recipe to affect the chemical reaction. Perhaps changing the ingredients or ratios will increase the bath fizzes even more. I’ll post more on our Bath Bomb Science Adventures soon!

Homemade Avengers Bath Bomb Recipe with the science behind the fizz



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