|MadSci Network: Chemistry|
Frankly, I'd never heard of this phenomenon, so I tried it. By golly, it works! Remember that all soap contains water, both in the form of water vapor inside trapped air bubbles (particularly important in the case of Ivory) and water that is caught up in the matrix of the soap itself. The effect is caused by the heating of the water that is inside the soap. The water vaporizes, forming bubbles; the heat also causes trapped air to expand. Likewise, the heat causes the soap itself to soften and become pliable. The result: the expanding gases form bubbles that stretch the softened soap, forming a large closed-shell foam. When the heating stops, the soap hardens again. It's actually very similar to what happens when popcorn pops. Incidentally, I tried some of the "puff", and found that it is still soap. Just soap that foamed and then solidified.
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