Working in coal fire.

   It's must be about twenty years ago now that the group of Carolina farriers who would eventually come to be known as S.H.O.E. organized their first big open clinic event.

   It was at this first event that one of the young farriers decided to break out his new prize...  An antique roll-out coal forge with hand-crank blower in remarkably good shape.  Like most modern farriers, he was accustomed to working in a propane forge, where you simply open the valves, push the ignition button, and go to work.  But he'd seen some of us "coal guys" start our forges.  He poured in a bunch of good coal, stuffed a wad of newspaper in over the grate, set it aflame, and commenced to cranking...  And in about half a minute the paper was burned up and the forge was still cold.  He tried my trick of pouring a bit of motor oil onto the paper on the next try, which got it to burn maybe a minute with him cranking away before it was gone.  At this point, his patience was failing, and he went into the shed and came out with a can of gasoline...

   I quietly backed off.  Way off.

   He saturated his coal with gas, tossed-in a match, and, despite the WOOF! that followed, stood his ground, cranking like a madman...  The result was an awesome pillar of fire straight out of Exodus!  But it only lasted a few minutes before the gas was gone, the coal barely warmed, and our hero was standing there exhausted, eyebrows gone, and hat brim smoking.

   Later I took pity on the guy and got a scoop of glowing coke from my forge, put it over the grate of his, and cranked easy until he had a decent fire started.

   Forge fires are a bit more complex than they look...

   The core of a forge fire, the part that actually heats metal, burns coke.  But the fuel blacksmiths and farriers put into their forges is usually hard coal.  (Ideally small chunks, called pea-coal.)  So how do we put-in coal, but burn coke?

   Coke is made by essentially cooking the "green" coal on the outer edge of the fire.  This process turns the hard coal into coke, which is kinda' like black popcorn.  As the the coke is consumed in the fire, new coal is added to the pile on the outside.  This is wet-down, and gradually pushed toward the center, driving freshly-cooked coke into the core.

   The coal in the forge also serves as an insulator, keeping the core of the fire contained.  Water is used to keep surface flames down, and to encourage slow coking rather than outright burning of raw coal.

   Coke starts easier and burns cleaner than coal, and should be the only material in contact with the heated portion of steel in the forge. 

   Starting a forge with coke is fairly easy...  Tear and crumple up some paper, and place it in a wad directly on the grate.  Pull a bit of coke over the paper.  Don't completely bury it.  Maybe drizzle a little motor oil onto the paper and give it some time to saturate in if you can.  Light the paper and let the fire spread a bit, then use your blower to produce a low-powered blast.  A hard blast might burn-up the paper before the coke has a chance to catch, or just plain blow-out the fire.  As the paper burns away and coke starts to burn, rake more coke onto the flames.  When you first start the fire, especially if you pull a good bit of green coal in with your coke, you may get a lot of thick smoke.  This will abate when the fire starts burning properly.  Do not stand in the thick smoke.  Not only is it rough on your lungs, but it is flammable...  Sometimes coal forges "poof" from smoke to a proper fire as the smoke suddenly burns-off.

   If you have a just bought or built a new forge and don't have any coke to get you started, you're going to need something to burn a slow, hot fire to get your coal started.  Not only are gasoline and kerosene dangerous, they burn far too fast and will be consumed before the coal is heated-up enough to start burning on its own.  Try using paper to start a fire of dry wood chips, maybe mixed with barbecue charcoal on your grate, with a bit of coal mixed-in, raked-in around the sides, or sparsely stacked on top.  Use the blower gently to get the fire going.  You need to cook the coal before it'll really burn on its own.

    Once you get a forge fire really going, the coal/coke for the first inch or so above the grate will actually be cooled by the air blast from the blower.  This is a good thing, as it keeps the grate from being burned-out.  The burning coke above this zone will be the core of the fire, where you will place metal to be heated.  Heaping more coke over the top of the core will help contain and concentrate heat.  Fresh coal is occasionally added to the outer edge of the pile, and  a sprinking can or squirt bottle is used to dampen it.  As the fuel in the core is consumed, the smith slaps the sides of the pile with a shovel or  tool to push more coke into the core and fresh coal toward the center to be coked. 

   Mineral impurities in the coke and water used in the forge (silica, metals, etc.), along with oxidized traces of the steel being worked, melt and flow to the "cool" zone just above the grate, where they solidify into clinker.  Chunks of hard stuff that block your blower blast and foul-up forge function.  These have to be removed from time to time during a smithing session.

   Effectively working in coal fire takes a bit of practice.  It also takes some caution, as coal burns hotter than propane, and leaving steel in too long can incinerate it.  But coal does have its advantages, so fire it up, be careful, and enjoy the old-school way of getting it done.