"Paul Héroult had none of the attributes of the traditional scholar. He was highstrung, unruly, occasionally hard and insolent; he did not fit the image of wise, disciplined men of science. He loved games, the company of women, travels by land and sea; he was a free spirit in an impetuous body. No comparison with the austere scientist, struggling with stubborn mysteries. His discoveries were not the result of long sleepless nights spent in a laboratory, or of complicated scientific demonstrations. Héroult loved life, and could not have borne such restrictions. Instead, his inventions appeared suddenly, out of the blue, a stroke of common sense, or of genius, sometimes during a lively game of billiards, his favorite pastime.
Paul Héroult read Henri Sainte-Claire Deville's treatise on aluminium, when he was 15 years old. At that time, aluminium was as expensive as silver. It was used mostly for luxury items and jewellery. Héroult wanted to make it cheaper. He succeeded in doing so when he discovered the electrolytic aluminium process in 1886. The same year, in the United States, Charles Martin Hall (1863-1914) was discovering the same process. Because of this the process was called the Hall-Heroult process.
Héroult's second most important invention is the electric arc furnace for steel in 1900. The Héroult furnace gradually replaced the giant smelters for the production of a variety of steels. In 1905, Paul Héroult was invited to the United States as a technical adviser to several companies, and in particular to the United States Steel Corporation.
Paul Héroult is renowned for other major inventions among which a self-sustained conduit still used to bring water down from mountain heights and across rivers to hydraulic power plants, avoiding the need to build expensive bridges.