Subscribe to Make Magazine Today!

271165_148849715262786_1393994016_n

By way of the World’s Coolest Things’ Facebook page comes this “I HAVE to try this” microwave trick. Apparently, this is what happens when you microwave a bar of Ivory soap. It expands in a foam up to six times its original size. Not sure why it has to be Ivory.

Ivory Soap Trick

Gareth Branwyn

Gareth Branwyn

Gareth Branwyn is a freelancer writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor for Boing Boing and WINK Books. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.


  • Blaise Pascal

    Dove has 1/4 cleansing cream, not Ivory.

    Ivory soap has two claims to fame: it was tested and found to be 99.44% pure soap; and it floats rather than sinks in water. It was originally made accidentally when someone left a soap mixing machine run overnight. The resulting batch was pure white in color and floated because of all the entrained air.

    That’s why it foams: the soap heats and softens, and the air bubbles heat and expand, when it cools, the soap hardens again and the air bubbles don’t collapse.

    • Gareth Branwyn

      Oops. You’re right. That’s Dove. And just what IS “cleansing cream?”

      (I removed that reference.)

  • http://trkemp.wordpress.com trkemp

    My son tried this with Irish Spring. The stench made us leave the house for several hours and we had to get a new microwave because the smell never left it. In addition it hardly foamed up at all.

    • http://www.variousconsequences.com jstults

      Ha! We tried Irish Spring too; it was terrible!

      To get rid of the smell, and make the microwave suitable for food again we did several cycles of “steam cleaning”: nuke a cup of water for several minutes. The steam and water that gets splashed all over when it boils does a good job of loosening up any bits of soap that got thrown about.

      We also tried the Ivory: much better, just grows, doesn’t explode, and doesn’t smell awful.

  • http://ravenlunatick.wordpress.com Raven

    Awesome! I just did this with my kids. It smelled some, but hopefully it goes away…

    • Gareth Branwyn

      How much volume did you get? I’m anxious to try this myself. Have to go get some Ivory soap.

    • Gareth Branwyn

      Whoa. I just watched your video, Raven. That is SO cool. Definitely want to try this.

      • http://ravenlunatick.wordpress.com Raven

        It was sooo cool. I didn’t leave it in the recommended length of time (90 – 120 secs), so there is some bar left in the middle. And the smell is gone now, I can imagine how much Irish spring would reek. I can’t stand the smell of it. :P~~~

  • Pingback: Microwaving Ivory Soap « Raven Lunatick()

  • yahoo

    yup works on tesco value soap too. worked that out trying to melt and pour. oh and don’t leave it in too long or it starts burning an that really doesn’t smell good

  • t-bird

    I wonder if you can expand it into molds, like a giant rubber ducky or something

  • http://www.facebook.com/srfarkas Stevan Farkas

    from the source article; Cut or break off a piece of Ivory™ and examine it. Do you see pockets of air? The air that causes Ivory™ to be less dense than water has been whipped into the soap, so you won’t see bubbles or pockets of air. This is important, because it’s the reason why the soap trick works.

Related Supplies at Maker Shed