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40 ADVANCED MATERIALS & PROCESSES • SEPTEMBER 2014
T wo young men living an ocean apart—both
just 22 years old—invented the same novel
process for reducing aluminum from its ore.
One was an American chemist, Charles Martin
Hall, and the other was a French metallurgist, Paul
Heroult. Both lived from 1863 to 1914. Their new
process would remain the world’s method for mak-
ing aluminum for the next 100 years and beyond,
and propelled aluminum and its alloys into second
place as the most widely used structural metal, just
after steel.
The driving force behind the search for low-
cost aluminumwas not demand for the product, but
knowledge of the vast resource of aluminum-con-
taining minerals in easy reach within the earth’s
crust. It had long been known that large deposits of
aluminum-containing clays constituted great quan-
tities of aluminum, especially in ores called bauxite
named after a region in France called Baux where
the ore was first identified. Bauxite is widely scat-
tered around the globe, mostly in tropical climates.
Charles Martin Hall
Charles Martin Hall was born in Thompson
Township, Geauga County, Ohio, in December
1863. The Hall family moved to Oberlin, Ohio,
about 35 miles southwest of Cleveland, when the
children were old enough for college. Even though
Oberlin College is primarily a liberal arts school, a
number of science courses were taught including
chemistry by Professor Frank Fanning Jewett, and
Hall took his courses.
After graduating in spring 1885, Hall set up his
now-famous experiments in a woodshed behind
the family home with the assistance of his sister
Julia, also an Oberlin chemistry student. In just a
few weeks in the winter of 1886, Hall developed his
method for making aluminum. His invention en-
tailed dissolving aluminum oxide in the mineral
cryolite. The molten bath was contained in a pot
lined with graphite and with graphite electrodes in-
serted into the bath. A low voltage/high amperage
electric current was passed from the electrodes to
the lining, where aluminum metal was separated
from the oxide. Aluminum collected at the bottom
of the pot and was drained off periodically.
He immediately started applying for patent
protection for his invention, which required find-
ing money and hiring a patent attorney. His patent
was formally filed on July 9, 1886. However, the
U.S. Patent Office notified
Hall that another applica-
tion for the same process
had been filed on April 23,
1886, by a Frenchman
named Paul L.T. Heroult,
meaning that Heroult’s
patent application predated
Hall’s by more than two
months. This patent inter-
ference was resolved when
Hall proved that he had re-
duced his invention to practice on February 23,
1886, where Heroult had only his filing date of
April 23, 1886. Hall, therefore, became the inventor
of record in the U.S. by a mere two months.
Hall then set out to find financial supporters to
carry his process into production. His first success-
ful contact was with the Cowles brothers who
owned the Cowles Electric Smelting and Alu-
minumCo. of Cleveland. The Cowles had a process
for making an alloy of copper containing alu-
minum called aluminum bronze. Hall joined the
Cowles Co. at their plant in Lockport, N.Y., with a
salary of $75 per month for three months. If his ex-
periments were satisfactory after that time, he
would receive $750 and the company would con-
tinue to support his work. An option for further re-
wards was never fulfilled due to disagreements
between Hall and the brothers. Hall parted com-
pany with the Cowles before making progress in
aluminum production.
However, Hall had worked with a manager at
the Cowles plant, Romaine C. Cole, who had done
some work on aluminum for a testing company in
Pittsburgh named Hunt and Clapp. When it be-
came clear to Hall that the Cowles were not sup-
porting him, Cole recommended that they contact
Captain Alfred E. Hunt. Cole arranged a meeting
with some of Hunt’s acquaintances in July 1888 to
Metallurgy Lane,
authored by
ASM life member
Charles R. Simcoe,
is a yearlong series
dedicated to the early
history of the U.S. metals
and materials industries
along with key
milestones and
developments.
Aluminum: The Light Metal—Part I
Aluminum, one of the most widely used structural metals in modern industry,
is produced in quantities exceeded only by steel. Its light weight, corrosion
resistance, high strength after heat treatment, and global availability of bauxite ores
make aluminum attractive for everything from kitchen utensils to spacecraft.
Charles Martin Hall
in 1905, age 42.
Courtesy of
.
Paul Heroult.
Courtesy of
.