From Candles to Soap :

n 1879, Procter and Gamble's best seller was candles. Yes, they made candles...
But the company was in trouble. Thomas Edison had invented the light bulb, and it looked as if candles would become obsolete. Their fears became reality when the market for candles plummeted since they were now sold only for-special occasions.
The outlook appeared to be bleak for Procter and Gamble. However, at this time, it seemed that destiny played a dramatic part in pulling the struggling company from the clutches of bankruptcy. A forgetful employee at a small factory in Cincinnati forgot to turn off his machine when he went to lunch. The result?
A frothing mass of lather filled with air bubbles. He almost threw the stuff away but instead decided to make it into soap. The soap floated. Thus, Ivory soap was born and became the mainstay of the Procter and Gamble Company.
Why was soap that floats such a hot item at that time?