There is a black rock that can catch fire and burn so hot it can make straight rods of steel bloom into latches, hinges, or even roses. That sounds like one of those teasing jokes adults tell kids. How silly.
But true. We use coal, the fuel that became the favorite of 18th century north American blacksmiths, in our shop to heat our forges. There is coal near where we live, but to get Sewell coal we have to hire a driver with a dump truck and go on a six-hour round-trip journey with him along twisting rural two-lane blacktop. The mine is underground in southeastern West Virginia, where the Sewell coal seam is wide. Sewell coal, with its low ash and sulfur content and its superior coking properties, is worth all the trouble it takes to get. Yet, because it is so hard to get and because we hope to make our carbon footprint as small as possible, we are glad that a little coal goes a long way in our forges. We are still using the four tons we bought in 2002.
In our shop, as we heat and hammer the steel, our fires are tools which must be used attentively. Without this attention the lower part of the fire could burn away, make cold spots, clinkers; gooey masses of impurities, and hot spots capable of burning tips off finials in an instant. We must consistently feed the fire, pushing pieces of unburned green coal close to the fire's edge where they can kindle and become coke. There must always be enough coke when the fire is pushed apart at the end of the day so that there is ample fuel to start the next day's fire.
Our shop has three forges, each with an anvil and complete set of tools. Each work station is devoted to a specific range of tasks.
Just behind the forge hood is the hand-operated blower used to blow air up through the bottom of the fire. The air blows into the fire from the bottom of this cast iron firepot through the tuyere, which is connected by pipe to the hand-operated blower.
The firepot has a clinker breaker, shown at center. The border surrounding it is the opening for air.
We use Sewell coal, named for the seam underground where it is mined. It is bituminous coal with low sulfur and ash content. It burns extremely hot and readily forms coke.
Our coal fire is actually a coke fire, the coal we place around the edges becoming the coke that burns with great heat in the center of the fire.
This piece is half coke, half coal.
When all the impurities burn off, the coal has become coke. It is feather light and capable of heating steel to forging temperatures of 1,600 degrees fahrenheit and above.
Coke doesn't smoke or flame when it burns as coal does.
Each blacksmith has his or her own way to light a fire. Molly starts by emptying the firepot, then filling it with newspaper topped by twigs. During damp winter weather a candle lights it better than a match does.
Once the paper is burning well, we place coke and partially burned, partially coked coal on top of it, all the while turning the blower handle to provide plenty of air.
The smoke and flames are from pieces of fuel that haven't yet completed the transition from coal to coke.
When the fire looks solid and steady we add some green coal near the edges and start work.