Put a bar of soap in the microwave and watch it expand to 6x its size right before your eyes! The Expanding Ivory Soap Experiment is a classic science activity that will fascinate kids and grown-ups alike.
The Ivory Soap experiment is one of my favourite science experiments for kids because it’s so quick and easy, and it yields such fascinating results. There’s almost no prep required, and you don’t need any fancy supplies. All that’s required is a bar of Ivory and a microwave oven.
What happens when you put a bar of Ivory soap in the microwave?
Well, because of the high volume of air whipped into a bar of Ivory soap, when the soap is heated, it rapidly expands into a huge, fluffy cloud in seconds.
Who would’ve ever thought to put a bar of soap in a microwave I wonder?
I have no clue, but I’m glad they gave it a try because they discovered one of the best-ever science experiments for kids!
Can I do the experiment with other brands of soap?
**A word of warning. This expanding soap experiment should only be done using Ivory soap. The high air content in the Ivory brand is what makes the experiment work.
If you use a different brand, your soap may not expand, and could even smoke and burn and ruin your microwave.
There’s no fear of that happening if you use Ivory.
Let me show you how you can do this awesome experiment at home or in your classroom, and at the end of the post, I’ll suggest a few ways to use your fluffy, soapy results.
You’ll need 3 things to conduct the Ivory Soap Microwave Experiment:
For your convenience, this post contains affiliate links.
- bar of ivory soap (do not try this with any other brand of soap)
- microwaveable dinner plate
Before you begin, you can take a few minutes to let the children examine the bar of soap. Use descriptive words as you take turns holding it, feeling it and smelling it.
Did you know that Ivory soap floats? It really does! That’s because of the high air content I was telling you about earlier.
If you have an extra bar of Ivory, you could drop the spare bar into a bowl of water to show the children how buoyant it is.
**I wouldn’t wet the bar that you’re putting in the microwave. I’m not sure how that would affect the science experiment.
How to do the Ivory Soap Experiment:
- Place your Ivory on a microwaveable plate
- Put your soap in the microwave
- Run microwave on high for 1-2 minutes. Today I set my microwave for 1:20. You can’t really overcook your Ivory, but it will reach a point where it stops expanding.
You’ll want to pull up a chair or stool for your child to stand on so they can watch the ivory expand right before their eyes.
It happens so quickly! It’s fascinating!
The Ivory will start to expand at about the 15 second mark. To see it rolling, writhing and expanding as if it were alive is really exciting!
When your microwave stops, remove the soap and examine it.
Caution! The plate and soap will be quite hot for a minute or so after being removed from the microwave. They cool down quickly, but give the soap a few minutes before letting your children handle it.
Doesn’t your kitchen smell amazing?
Don’t worry, that smell should leave your microwave quickly, and it will not affect the flavour of any cooking you do.
You can always microwave a cup of water with vinegar or lemon juice added to get rid of the smell.
I personally love the smell of Ivory soap. It takes me back to my childhood. Ivory was the gentlest soap back when I was a kid, so we used it for years as children. Because the scent brings back warm memories, I don’t mind that my kitchen smells like Ivory after doing the experiment.
If you think the soapy smell might bother you, open a window before microwaving your bar of soap.
Examining your fluffy Ivory soap cloud:
Once your soap has cooled off, it’s time to have some fun!
Let your children investigate how the soap has changed: what started out as a hard bar of soap is now a fluffy, crumbly powder.
Today, to let the children really explore the results of our experiment, I placed our puffed up soap in a large baking dish and the girls chopped it all up with paté knives.
They also rubbed it between their hands to crush and crumble it. This is such an amazing sensory experience. The soap is so smooth and silky. It feels lovely, and it smells incredible!
Be sure to warn children not to put the powder in their eyes, nose or mouth. It IS soap after-all, and it would sting the eyes, and taste horrible.
What can you do with the results of your Ivory Soap experiment?
We usually do this experiment when it’s time to make a new batch of Homemade Laundry Detergent. I make it with Ivory, Borax and Washing Soda.
The kids love helping me make laundry soap, and it’s a great way to use the results of this experiment.
Our favourite way to use our crumbled soap though, is for sensory play!
We grab a roll of toilet paper and some water and the hooligans whip up a clean mud, also known as ghost mud or fairy mud. It’s a moldable dough that smells wonderful and keeps the kids entertained for hours.
Why does Ivory Soap expand in the microwave?
To find out the scientific reason why the Ivory Experiment works, head over to Steve Spangler Science, and he’ll explain the science behind it.
Looking for more easy, inexpensive experiments to do with your kids? Try our:
Get my latest e-book: Fizz, Pop, Bang! Playful Science and Math Activities
40 hands-on, learning activities for kids ages 3-8. Recipes, experiments, art projects, printables and play ideas with links to 80 activities not featured in the book.
Jackie is a mom, wife, home daycare provider, and the creative spirit behind Happy Hooligans. She specializes in kids’ crafts and activities, easy recipes, and parenting. She began blogging in 2011, and today, Happy Hooligans inspires more than 2 million parents, caregivers and Early Years Professionals all over the globe.