World's Biggest Bath Bombs (Galaxy and Rainbow Colored) - 37lbs Each! for Charity




Introduction: World's Biggest Bath Bombs (Galaxy and Rainbow Colored) - 37lbs Each! for Charity

About: I'm here to make a difference through STEM! :) I run an after-school STEM (Science, Technology, Engineering, and Math) program that serves 900+ low-income, minority students. My students are always in n...


My team and I created and detonated TWO 37lb bath bombs - galaxy-colored (inspired by this picture) and rainbow-colored - for your entertainment and for a good cause! We're using it to promote our back-to-school giveaway for 500+ low-income kids. Here is our campaign:

I run an after-school STEM (Science, Technology, Engineering, and Math) program that serves 900+ low-income, minority students. My students are always in need of school supplies at the beginning of the year so we're trying to raise awareness for this cause. We'd really appreciate it if you could help in any way, even if it's through sharing the video with your friends and family. :)

Youtube Video:


Bath bombs are basically a reaction between baking soda, also known as sodium bicarbonate, and citric acid. When combined, they produce sodium citrate and carbonic acid, which is then broken down into water and carbon dioxide - the molecule responsible for all that fizzing!

Step 1: Gather Your Materials

To make the World's Largest Bath Bombs, you'll need a LOT of materials. We made two, but here are the materials you'll need to make one giant bath bomb:

  • 20 lbs Baking Soda
  • 20 lbs anhydroud Citric Acid
  • 5 bottles of 91% isopropyl alcohol - 32oz
  • Set of food coloring gels (Warning: Gel food pastes may cause staining)
  • Some measuring equipment: scales, thermometers, and measuring cups
  • Containers (Seven 5-gallon buckets with lids, 7 empty water bottles with holes drilled inside)
  • 4 Mixing rods
  • 4 Power drills (3/8" or 1/2")
  • 2 Acrylic domes - 12" in diameter
  • Protective gear (aprons/lab coats, gloves, and face masks)

And make sure to work in a well-ventilated area!

Step 2: Grind the Citric Acid

While making our bath bombs,we want to make sure it has a lot of fizzing action, which means we’ll have to increase the rate of carbon dioxide gas being produced.

Therefore, you should grind the citric acid into fine powder. By increasing the surface area of our reactants, we increase the number of reaction sites.

Then pour the baking soda and citric acid in a 1:1 ratio inside the 5 gallon buckets.

Step 3: Create Colorant Solution

Mix the coloring gels in 1 cup of hot water. Then add 1 cup of 91% isopropyl alcohol. Then transfer it to a water bottle with holes drilled in the cap.

Step 4: Mix the Dry and Wet Ingredients

Attach the mixing rod to the power drill. Our mixing rod (2-3/4" in width) fits a 3/8" or 1/2" power drill.

Then mix the dry ingredients with the colorant solution. I recommend having 1 person pour the colorants while another person is mixing with the power drill. Have the other person slowly squeeze the colorants into the dry mixture and mix. Continue doing so until you get a deep, vibrant color. If the mixture starts to foam, you are adding the liquid too fast.

Step 5: Stop When You Get the Texture of Damp Sand

Stop mixing when it has the consistency of damp sand. If the mixture is too wet, try adding a little more baking soda and citric acid until the consistency is correct. If it is too dry, add more colorants.

Step 6: Fill the Mold by Layering the Colors

Now we’ll fill the molds by layering the colors. We want to make sure it’s compact. Once one half of the acrylic mold is filled, begin layering other colors into the other half of the mold. Slightly overfill the last color in each mold.

Step 7: Press the Molds Together

Have one person hold each part of the mold. Then firmly press the two halves together.

Step 8: Let It Dry

Let it dry for 4-5 hours. If you try to remove the bath bomb while it’s still soft, it can crumble. Allowing the bath bomb to dry thoroughly in the mold will make it easier to remove and handle.

Meanwhile, entertain yourself with a giant inflatable emoji ball.

Step 9: Take Out Your Bath Bomb

Remove your bath bomb from the mold.

Then weigh it. Our bath bombs weighed almost 37 lbs each!

Step 10: Detonate!

Now drop your giant bath bomb in the bath tub!

I recommend running a hot bath before detonating the bath bomb. The higher temperature increases reaction rates, producing more bubbles!

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    5 Discussions


    4 years ago

    Awesome, I have one question, if I make like 20 of this but smaller size and throw them lets say in a pool with some people, anything wrong could happen? I dont have a minimal idea about chemistry and stuff, thanks!


    Reply 3 years ago

    Hi CarlosE78! :) Sorry for the delayed response.

    Are you doing this in
    a public swimming pool or private swimming pool?

    The biggest concern is staining. I used food
    coloring gels because they’re inexpensive and produce vibrant colors. Unfortunately, the highly concentrated colorants will result in a lot of staining. My bathtub is made of ceramic so it's pretty stain-resistant. Our skin isn't as stain resistant but it does shed. :p The materials of the swimming pool may not be stain resistant either.

    Another concern is irritation. The products of this reaction are water, carbon dioxide gas,
    and sodium citrate. Sodium citrate may cause irritation through prolonged
    contact. Check out the MSDS (Material Safety Data Sheet) for more

    Finally, the amount of carbon dioxide released will lower the pH of the pool water and make it slightly more acidic. That has various consequences as well.


    Reply 3 years ago

    At a friends party a few years ago and his kids threw 3 or 4 of them into the pool and he had to do a complete water change and filter medium replace because of it.
    Of course, if it's not your pool.....


    4 years ago

    That looked like it was really fun!


    4 years ago

    Very cool! My kids would love to make something like this. Thanks for sharing how you did it :)