Watch Soap Grow!
Microwave an Ivory soap bar on a microwave-safe plate with adult supervision to watch it expand into fluffy foam, exploring trapped air and physical change.
Step-by-step guide to make Ivory soap expand in the microwave
Step 1
Gather all materials and bring them to the kitchen counter.
Step 2
Find an adult and ask them to help with the experiment.
Step 3
Open the microwave and place the microwave-safe plate inside.
Step 4
Unwrap the Ivory soap bar and remove any packaging.
Step 5
Put the soap bar in the center of the plate.
Step 6
Ask the adult to set the microwave to high for 1 minute 30 seconds and press start.
Step 7
Stand back and watch the soap expand through the microwave window while the adult supervises.
Step 8
When the microwave stops, wait 30 seconds before opening the door.
Step 9
Ask the adult to use the oven mitt or towel to remove the hot plate and set it on the counter.
Step 10
Let the fluffy soap cool for one minute before doing anything else.
Step 11
Gently press a small corner of the cooled foam to feel how light and airy it is.
Step 12
Share a photo or description of your grown soap on DIY.org.
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can we use if we can't find an Ivory soap bar?
If Ivory isn't available, use another plain, dry solid bar soap that lists no moisturizers (for example Fels-Naptha or Zote) because the experiment needs a non-moisturizing, air-filled bar rather than a gel or lotion soap.
The soap didn't puff up in the microwave — what might have gone wrong and how can we fix it?
If it doesn't expand, make sure you used a dry Ivory or plain bar (not a moisturizing or gel soap), placed it in the center of a microwave-safe plate, and have the adult run additional short 10–15 second high bursts while supervising and watching through the microwave window until it puffs.
How can we adapt this activity for different ages?
For preschoolers, the adult should do all microwave and hot-plate steps while the child watches and later gently presses a cooled corner, and for older kids let them set the 1:30 timer under supervision, remove the plate with an oven mitt, and photograph or describe the grown soap for DIY.org.
How can we extend or personalize the grown soap after the experiment?
Once the fluffy soap has cooled for one minute, press cookie cutters or gently carve shapes with a plastic knife, measure and record the height change, then take a photo of your decorated or shaped soap to share on DIY.org.
Watch videos on how to make Ivory soap expand in the microwave
Soap Making Tutorial and Recipe for Absolute Beginners (you can do it!)
4 Videos
Soap Making Tutorial and Recipe for Absolute Beginners (you can do it!)
WHY DOES SOAP MAKE BUBBLES? / Science for kids
How soap Bubbles are made | Science Experiment | Kurious Kid
Bubble Magic 🧼: The Science of Surface Tension | How Soap Bubbles Work for Kids | Fun Science Lesson
Facts about kitchen science and microwave safety for kids
☁️ The grown-up-looking foam you get is mostly air — many foamy materials are over 90% air by volume.
🧼 Ivory soap was introduced by Procter & Gamble in 1879 and became famous for being "pure" and able to float because air was whipped into it.
🔬 Microwave ovens heat water molecules, turning water inside the soap into steam that helps trapped air expand the bar into fluffy foam.
🧪 The puffing of Ivory in the microwave is a physical change (it expands and reorganizes) rather than a chemical reaction, though overheating can char it.
👩🚒 This classic kitchen science demo teaches about gases and expansion — but always use adult supervision and a microwave-safe plate because hot soap and steam can burn.
How do you do the Watch Soap Grow! microwave experiment?
What materials do I need for the Watch Soap Grow activity?
What ages is the Watch Soap Grow experiment suitable for?
Is the Watch Soap Grow experiment safe and what precautions should I take?
One subscription, many ways to play and learn.
Only $6.99 after trial. No credit card required