Why does Ivory soap float?

Too much air caused Ivory soap to float. It was originally an error in production.

In 1878, Harley Procter and cousin James Gamble decided to create for their company a white soap that would rival the popular castile soaps of their competitors.

The product was successful. Then, in 1879, a worker mistakenly allowed the soap solution to be over-mixed.

The new version of the soap was an immediate success because it bobbed to the surface of the water.