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.