A Little Bit of Ironmaking History: By the late Middle
Ages, European ironmakers had developed the blast furnace, a tall
chimney-like structure in which combustion was intensified by a
blast of air pumped through alternating layers of charcoal, flux,
and iron ore. (Medieval ironworkers also learned to harness water
wheels to power bellows to pump the air through blast furnaces and
to power massive forge hammers; Molten cast iron would run directly
from the base of the blast furnace into a sand trough which fed a
number of smaller lateral troughs; this configuration resembled a
sow suckling a litter of piglets, and cast iron produced in this
way thus came to be called pig iron. Iron could be cast directly
into molds at the blast furnace base or remelted from pig iron to
make cast iron stoves, pots, pans, firebacks, cannon, cannonballs,
or bells (“to cast” means to pour into a mold, hence
the name “cast iron”). Casting is also called founding
and is done in a foundry.
The Clear Creek Furnace: This cut-stone furnace,
originally built in 1839 then rebuilt in 1872, is a relic of
Kentucky’s once flourishing iron industry. In the 1800's,
America was in need of iron for everything from household pots to
wheels for trains. In the 1830s, Kentucky ranked third nationwide
in pig iron production.
This furnace produced an average of 3 tons of iron a day
devouring half an acre of trees in the process. The surrounding
land, rich in natural resources, not only provided the iron ore but
also provided the necessary limestone and trees used in the iron
making process. Hand-cut limestone, stacked 40 feet tall with an
inside diameter of 10 1/2 feet, make up the chimney - the core of
the iron making process.
A small village complete with a store, school, laundry service
and church once sat on this site. Get out and explore the area,
where might the old wagons have traveled? Where would the water
channel have been that was used to power the magnificent bellows,
imagine the noise of the furnace and above it the sound of children
playing.
The Chemistry of Ironmaking: Although today's iron blast
furnaces are much more advanced, the process is basically the same.
The method for extracting pure iron from its ore is to heat the ore
in a blast furnace with limestone and coke(charcoal). The coke
(charcoal) reacts with iron oxide to produce pure iron, while the
limestone combines with impurities in the ore to form a slag that
can then be removed from the furnace: 3C + 2Fe2O3 + heat = 3CO2 +
4Fe.
To get credit for this Earthcache, please email me answers to
the following questions:
- What three natural resources were used in the ironmaking
process?
- What product was primarily made with the iron from this
furnace?
- Approximately how thick are the limestone blocks of the furnace
structure?