The businesses of the era dramatically increased the supply of aluminium, a plentiful resource not found in nature in pure form, and reduced its price. The Cowles process was the immediate predecessor to the Hall-Héroult process—today in nearly universal use more than a century after it was discovered by Charles Martin Hall and Paul Héroult and adapted by others including Karl Bayer. Because of the patent landscape, the Cowles companies found themselves in court. Judges eventually acknowledged their innovations many years after the companies formed, and one brother received two separate settlements.
Eugene H. Cowles and Alfred H. Cowles, sons of newspaper publisher Edwin Cowles of Cleveland, Ohio built high temperature furnaces during the late 1880s in Lockport, New York and in Stoke-upon-Trent in England based on the furnace of Carl Wilhelm Siemens. Charles F. Mabery, at the time of what is today the Case School of Engineering, contributed expertise in chemistry.
The family had purchased a copper zinc mine on the Pecos River in New Mexico in 1883. Eugene that year designed a furnace to extract zinc from the mine's ores. Two young employees were testing four furnaces in a Cleveland laboratory by 1885. Their first plant was built to extract aluminium, in 1886 using hydropower from a tailrace of Niagara Falls on the Niagara River.
Adolphe Minet wrote a sympathetic assessment twenty years later in 1905 from the perspective of Paris. The Cowles furnace was electrochemical, one of two kinds of processes applied to producing aluminum during the 19th century, and belonged to the electrothermic group that includes Héroult (alloys), Brin, Bessemer, Stephanite and Moissan (carbide). Minet thought Cowles was the first great advance in electrometallurgy at least for many years, calling it a "practical" furnace yielding alloy up to 20 percent aluminum. The first was begun in 1884 and the best was tested in Cleveland in 1886. Minet gave the real credit though to other chemists who saw how to produce "pure aluminum".
William Frishmuth, who as the sole aluminium supplier in the United States built the Washington Monument's aluminum cap in 1884, was one among those who worried that "foreign capitalists" were about to control the world aluminium market.
Charles Martin Hall was a graduate of Oberlin College in Ohio who had discovered in February 1886 an electrolytic process for aluminum extraction. His patent application in July collided with Paul Héroult's application for the same idea, "electrolysis of alumina in cryolite" and for which Héroult had received the patent in France in April. Hall proved his February date and was awarded the patent in the U.S. Hall made a licensing agreement and worked with the Cowles at the facility in Lockport with the hopes of moving his ideas from the laboratory into production.
Cowles did not choose to use the Hall patent. Their reason is unclear—some in Lockport remember it as disagreement about "external heat and copper electrodes" and "internally heated furnace and carbon electrodes", and Alcoa culture remembers it as an attempt to "suppress his new process by buying him out". Hall left after one year, in July 1988, to found the Pittsburgh Reduction Company which today is named Alcoa.
The Cowles facility in England became part of British Aluminium in the late 1880s. In 1893, after Eugene's death, Maybery questioned a presentation that to him indicated the Cowles patents were infringed by the carborundum process of Edward Acheson. In 1900 Cowles received a $300,000 payment from the carborundum company. The judges' decision gave "priority broadly to the Messrs. Cowles for reducing ores and other substances by the incandescent method".