Expanding or Crumbling Bath Bombs? Here’s Help!

packing in mold


When I first started making bath bombs, I got really frustrated! Some of my bath bombs expanded in the molds. Others cracked when I tried to remove them from the molds.

Bath bombs will expand in the mold when the mixture is too wet. However, if a bath bomb mixture is too dry, the bath bombs will crumble or crack when they are removed from the molds. A bath bomb mixture that is the proper consistency can hold its form when squeezed in a ball shape.

I’ve walked the road of hard knocks when it comes to learning how to make bath bombs. That’s why I can now tell you some shortcuts for how to make bath bombs the easy way.

Signs That Your Mixture is Too Wet


bath bomb ingredients


I remember making volcanoes in the backyard as a child. We would shape a mountain out of clay and then dig a hole down the middle. We’d put some citric acid and backing soda in the hole and then pour in water.

“Woah, Nelly!” All us neighborhood kids would scream in wild delight as we watched the explosion.

If your bath bomb mixture is expanding in the mold, it’s likely because the mixture is too wet. When your mixture is too wet, the citric acid and baking soda will react just like a backyard volcano.

The idea here is that you want your bath bomb to “explode” in the tub water and not before. However, you do need some amount of moisture to hold the bath bomb mixture together. So when adding liquid you need to go very, very slowly to ensure you don’t overdo it.

Other signs that your bath bomb mixture is too wet are that your bath bombs may not fully harden and they might not fizz as much as you’d hoped.


Signs That Your Mixture is Too Dry


winter wonderland


Equally frustrating can be a bath bomb mixture that is too dry. It’s happened to me plenty of times. I thought I’d made the perfect bath bombs. I excitedly yet patiently waited for them to harden, only have them to crumble to bits when I tried to take them out of the molds.

Or worse, my bath bombs were absolutely gorgeous–except for the giant crack that runs through each of them. Ugh!

When a bath bomb mixture is too dry, it is almost impossible to get out of the mold. Bits of the bath bomb might even stick to the mold. Super annoying!


Get Your Bath Bomb Mixture Just Right


How to make bath bombs


Remember Goldilocks? She comes across three bowls of porridge. One is too hot. One is too cold. And the third is just right. I always think about Goldilocks when I’m whisking my bath bomb ingredients.


7 Tricks for Perfect DIY Bath Bombs


To get the mixture just right, you’ve got to be sure it’s not too wet and not too dry. And you’ve got to make sure the chemical reaction doesn’t happen too soon.

Here are some tricks for getting your mixture just right, so that you can finally experience bath bomb glory:

  1. Use powdered mica instead of liquid dye for the colorant. This makes a huge difference.
  2. Use the witch hazel sparingly, one spritz at a time. Mix well after each spritz to see if the mixture is perfect.
  3. Add the liquids at the very end of the recipe. This gives the wet ingredients less time to react with the dry ingredients before you pack the mixture into the molds.
  4. Do the snowball test with your bath bomb mixture. Make a ball of it just as you would make a snowball. Then drop the ball and be sure the mixture held its shape. If not, it’s still too dry, so you’ll want to add a spritz of witch hazel and test again.
  5. The longer you dry your bath bombs, the better the chance they’ll hold together when you remove them. Place bath bombs in a low-humidity location to dry and don’t peek early. Be patient!
  6. If you find that your mixture is expanding in the mold, wrap a rubber band and around the mold before you leave it to dry.
  7. Once your bath bombs have hardened, gently tap all around the outside of each mold with the back of a metal spoon. This will release the hardened bath bomb from the mold making it easier to remove.


More Resources for DIY Bath Bombs


If you struggle with crumbling bath bombs or expanding bath bombs, you may still be a bath bomb beginner. Take pride! We’ve all been there. You can accelerate your path to success by reading up. Read How to Make Bath Bombs for Beginners to learn how to make a perfect starter bath bomb and then 10 Best Essential Oils for Bath Bombs to discover how to add both essential and carrier oils for aromatherapeutic bliss in the tub!


Tags: bath bomb mixture consistency, bath bomb mixure, bath bombs crumble, bath bombs expanding in molds, bath bombs stick to molds, crumbling bath bombs, diy bath bombs, expanding bath bombs, homemade bath bombs, how to get a good consistency for bath bomb mixture, mixture is too dry, mixture is too wet, snowball test, test for conistency


Shana Burg is a bath enthusiast, content strategist, and award-winning writer. She is the founder of bathtubber.com.

Recent Posts