What Makes Floating Soap Float?
Floating soaps are made by whipping air bubbles into the warm soap mixture. The air decreases the soap’s density, enabling it to float. Floating soap is the result of a lucky mistake.
In 1863, a workman went to lunch, leaving the machinery mixing a batch of soap turned on. When he returned, he found that more air than usual had worked its way into the soap. He didn’t want to admit his error, so he poured the mixture anyway.
Floating soap became an immediate success, since bathers no longer had to hunt for their soap in murky bath water. The only commercial bar soap on the market as of 2015 that does float is Ivory.
A popular experiment in grade school classrooms involves comparing different soaps to see which ones float. The bars are simply placed, one at a time, in a bowl of water. As expected, the Ivory bar is a “floater.”
Variations of the experiment involve heating the bars of soap in a microwave before dropping them in the water. Since the application of heat makes the bars expand and grow slippery, they become less dense and when placed in water, they may float.