Today, ancient African ingenuity gives us steel.
The University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
Modern steel-making began in
1847. William Kelly of Eddyville, Kentucky, found
he could make superior structural iron if he blew
air through molten pig iron. Oxygen from the air
burned harmful elements out of the iron and formed
a very strong carbon steel. The process gave what
we call converter steel. Nine years later the
Englishman Henry Bessemer reinvented Kelly's
method. Today we talk about the Bessemer process
for making carbon steel.
But carbon steel had been made long before either
Kelly or Bessemer. One of the oldest and most
sophisticated methods was that of the Haya people.
They're an African tribe in what is Tanzania today.
The Hayas produced high-grade carbon steel for
about 2000 years.
The Hayas made their steel in a kiln shaped like a
truncated upside-down cone about five feet high.
They made both the cone and the bed below it from
the clay of termite mounds. Termite clay makes a
fine refractory material. The Hayas filled the bed
of the kiln with charred swamp reeds. They packed a
mixture of charcoal and iron ore above the charred
reeds. Before they loaded iron ore into the kiln,
they roasted it to raise its carbon content.
The key to the Haya iron process was a high
operating temperature. Eight men, seated around the
base of the kiln, pumped air in with hand bellows.
The air flowed through the fire in clay conduits.
Then the heated air blasted into the charcoal fire
itself. The result was a far hotter process than
anything known in Europe before modern times.
Anthropologist Peter Schmidt wanted to see a
working kiln, but he had a problem. Cheap European
steel products reached Africa early in this century
and put the Hayas out of business. When they could
no longer compete, they'd quit making steel.
Schmidt asked the old men of the tribe to recreate
the high tech of their childhood. They agreed, but
it took five tries to put all the details of the
complex old process back together. What came out of
the fifth try was a fine, tough steel. It was the
same steel that'd served the subsaharan peoples for
two millinea before it was almost forgotten.
This ancient African steel was the fruit of
unalloyed human ingenuity. This complex metal,
flowing from simple native elements, forms a mute
tribute to the power of the human mind over matter.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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