Coal Forges

A coal forge typically uses bituminous coal, industrial coke or charcoal as the fuel to heat metal. The designs of these forges have varied over time, but whether the fuel is coal, coke or charcoal the basic design has remained the same.

A forge of this type is essentially a hearth or fireplace designed to allow a fire to be controlled such that metal introduced to the fire may be brought to a malleable state or to bring about other metallurgical effects (hardening, annealing, and drawing temper as examples). The forge fire in this type of forge is controlled in three ways: 1) amount of air, 2) volume of fuel, and 3) shape of the fuel/fire.

Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood, sugar, bone char, or other substances in the absence of oxygen (see pyrolysis, char and biochar). The resulting soft, brittle, lightweight, black, porous material resembles coal and is 85% to 98% carbon with the remainder consisting of volatile chemicals and ash.
Coal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. It is composed primarily of carbon along with variable quantities of other elements, chiefly sulfur, hydrogen, oxygen and nitrogen.
Coke is usually produced from coal; the process is called coking. Volatile constituents of the coal—including water, coal-gas, and coal-tar—are driven off by baking in an airless furnace or oven at temperatures as high as 2,000 degrees Celsius. This fuses together the fixed carbon and residual ash.
Clinker is a general name given to waste from industrial processes — particularly those that involve smelting metals, burning fossil fuels and using a blacksmith's forge which will usually result in a large buildup of clinker around the tuyère. Clinker often forms a loose, black deposit that can consist of coke, coal, slag, charcoal, grit, and other waste materials. Clinker may be reused to make hard paths. It is laid and rolled, and forms a hard path with a rough surface. Clinker often has a glassy look to it; also note that it is much heavier than coke.

A clinker is coagulated slag or metal impurities that "melt" from the coal as it becomes coke. Most clinkers consist of pyrites that are naturally included in coal seams. Using "metallurgical" grade coal (met coal) greatly reduces clinkers. Clinkers will block air flow from the tuyere and that is why the firepot has a clinker breaker. Large clinkers will have to be removed with a poker.

Firepot with Tuyere, Clinker Breaker, and Ash Dump

Clinker breaker

Breakes up clinkers so they can be removed from the firepot.


The grate allows the coal ash to fall through the tueyre into the ash dump while keeping the burning coke and clinkers in the firepot.

From Wikipedia, a tuyere is a tube, nozzle or pipe through which air is blown into a forge. Air or oxygen is injected into a forge under pressure from bellows or a blower into thte firepot. This causes the fire to be hotter in front of the blast than it would otherwise have been, enabling metals to be smelted or melted or made hot enough to be worked in a forge. This applies to any process where a blast is delivered under pressure to make a fire hotter.

The blower is used to force air into the forge and through the burning coal in order to make the fire hotter (less air cooler, more air hotter).

There are several different types of bellows, but they all work according to the same concept. There are single-chambered bellows (made out of two teardrop shaped boards), hand-operated bellows (made out of leather and wood) and double-chambered bellows (the most efficient type and constructed out of two airtight chambers instead of one).

fire potThe fire pot holds the burning coal (or other fuel). It allowes the air to come into the fire via grate at the bottom of the pot. Ash from the burned fuel falls through the grate to the ash dump.

Fire Tools: You will need certain tools to manage the fire.
Forge Rake: - The poker should have a blade to allow you to push and pull coal onto the fire. I use two: one is the one we teach in the Blacksmithing-101 class and has a pointed blade with a goose neck; The other has the end of the poker flattened into a blade or spatula shape and just has a gentle curve to it. It is this 2nd one that I find most useful.

Forge poker: - It is handy to have poker which is just a long rod, with a 90° bend at the end, so that you can poke down to the bottom of the fire pot and open up where the air comes into the fire without really disturbing the fire very much.
Coal Shovel: - Get (or make) a good sturdy one. Many of the small fireplace/firestove shovels that are sold are fine for removing ash from the fireplace, but do not stand up to use around the forge. You may have noticed that some of the shovels in the School have been bent and otherwise mutilated, those are the ones I am referring to.
Pick-up Tongs: - A very light duty pair of tongs with long reins and very long thin bits. I consider these as part of my forge tool set. (They are not used to hold steel while hammering.) Use them to pick out pieces of clinker, adjust coke to critical locations, and most importantly, to fish out that small piece of steel that has slipped down toward the bottom of the fire pot.
Drip Cup: - A can or ladle (with holes in it) on the end of a long handle for watering the fire. (Be very very careful in watering the fire, it is very easy to crack your cast iron forge or fire pot.) Use the drip cup to gently water down the outside edges of the fire to keep it from getting too large or hot. You don't want to drown the fire, just control it's growth and temperature.
How to light a coal forge

Things You'll Need:
  1. Clear the fire pot of ash and debris from any previous smithing. While you are doing this, make sure that the feed from the bellows into the fire pot is clear.
  2. Separate the coke and clinkers, and put them in two separate piles. "Coke" is coal that has been used before and resembles popcorn. It burns hot, and it will form the center of your forge fire. "Clinkers" are the residue of coke, and they are of no use. They belong in the ash dump.
  3. Place six charcoal briquettes on the grate in the fire pot in a pyramid shape. Presoak them with lighter fluid before placing them in the forge to avoid an explosive reaction once the fire has been lit.
  4. Light the charcoal and let the flames die down a bit from their initial burst. Let them heat up before pumping air through the bellows. They should look like they are ready to cook on before you give them a few blasts of air.
  5. Mound the coke into the center of the fire pot on top of and around the charcoal and allow it heat up as you provide more gentle air with the bellows. If you are lighting a completely new fire, surround it with new (or "green") coal, but stand back because the fumes will be strong.
  6. Add more green coal when the core is lit. Your forge is now lit.

Tips & Warnings

Understand that the green coal produces the most smoke, while coke burns cleanly. Use a poker to make a hole in the top center of the pile, which will allow flames to escape and smoke-producing elements to burn away.

Read more: How to Light a Blacksmith Forge |

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