Coal was placed in the oven and burned under controlled conditions.
Very high temperatures and regulated air infiltration was important in coke production.
Plumes of smoke filled the air around the ovens.
At the end of the burning cycle, water was poured in the oven and this made the coke cool and crack.
It was then pulled from the oven and loaded on rail cars.
When the oven was reloaded with the coal, it self-ignited from the heat retained in the oven.
The resulting coke was mostly pure carbon and burned at a much higher temperature than coal.
The steel industry was the major market for the coke.
These photos were shot in March 1998.