Microwaving Soap Experiment

Microwave Ivory Soap Experiment

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 Microwave 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.

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Because of the high volume of air that’s whipped into it, when you microwave Ivory soap, it rapidly expands into a huge, fluffy cloud in a matter of 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!


No, 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 bar soap.



  • Bar of ivory soap (do not try this with any other brand of soap)
  • microwaveable dinner plate
  • microwave.


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.

Note: I wouldn’t wet the bar that you’re putting in the microwave.  I’m not sure how that would affect the science experiment.



Time needed: 3 minutes.

How to Microwave Ivory Soap – Experiment

  1. Unwrap your bar of soap

    Unwrap your bar of Ivory and place it on a microwaveable plate.

  2. Place in microwave

    Put your plate of soap in the microwave.

  3. Heat for 1-2 minutes

    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 eventually 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.


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 the 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.



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.


Disclaimer and Safety Precautions

Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.


  • Put on protective eyewear. Conduct the experiment on the plastic tray and in a well-ventilated area.
  • Keep a bowl of water nearby during the experiment.
  • Keep flammable materials and hair away from flame.
  • Avoid looking directly at burning magnesium to prevent eye discomfort.
  • Do not attempt to extinguish the solid fuel and magnesium — let them burn down completely. Do not touch the stove after the experiment — wait until it cools down.
General safety rules
  • Do not allow chemicals to come into contact with the eyes or mouth.
  • Keep young children, animals and those not wearing eye protection away from the experimental area.
  • Store this experimental set out of reach of children under 12 years of age.
  • Clean all equipment after use.
  • Make sure that all containers are fully closed and properly stored after use.
  • Ensure that all empty containers are disposed of properly.
  • Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
  • Do not replace foodstuffs in original container. Dispose of immediately.
General first aid information
  • In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
  • If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
  • In case of inhalation: Remove person to fresh air.
  • In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
  • In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
  • In case of injury always seek medical advice.
Advice for supervising adults
  • The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
  • This experimental set is for use only by children over 12 years.
  • Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
  • The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
  • The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
  • Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.


Dispose of the reagents and solid waste together with household garbage.

Additional information


Chemistry, Mathematics

Materials Needed

# 3 12-inch long metal rods or thick wire: copper, steel, brass, or other metal.
# 8 identical Styrofoam cups
# Something to boil water in (a pot or kettle)
# Stove
# 4 instant digital thermometers
# Pitcher or other large container that will fit in the refrigerator
# Water
# Notebook and pen




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