Choosing Coal or Charcoal for Your Forge

Start with what your fire actually needs

A forge fire has one job: to get steel hot enough to move, and to keep it there while you work. Mild steel starts to soften around 950°C, comfortable forging sits between 1,000°C and 1,200°C, and forge welding wants 1,250°C or better in a reducing atmosphere. All three of the usual solid fuels will get you there. What separates them is everything else — how quickly they light, how often you refuel, how much smoke drifts over the fence, how much clinker you dig out of the firepot at the end of a session, and what the whole lot costs per kilo.

If you work in a shed at the bottom of a suburban garden, that "everything else" matters far more than the peak temperature. A fuel that reaches welding heat in four minutes is no use if it also smokes out next door's washing line. So it pays to think about your workshop, your neighbours and your working habits before you commit to a pallet load of anything.

Charcoal: the friendly fuel for beginners and small gardens

Charcoal is wood that has been heated without air until everything but the carbon has cooked off. It lights quickly, burns cleanly, and produces almost no visible smoke once it is going. For anyone learning fire control, it is the least punishing option.

• Lighting: a handful of scrunched paper and a few small splits will have a charcoal fire glowing in five to ten minutes. No kindling lay, no waiting for a coal fire to establish.
• Heat: easily hot enough to forge and weld in a well-built firepot, though the sweet spot is narrower than with coal.
• Burn rate: fast. Expect to top up every fifteen to twenty minutes during heavy work, which makes it hungry and, per hour of forging, the most expensive of the three.
• Ash and clinker: light, soft ash and virtually no clinker. You can rake it straight onto the garden.
• Smoke and smell: minimal. A pleasant, faintly woody smell rather than the sulphurous bite of coal smoke.

Buy lumpwood charcoal rather than barbecue briquettes. Briquettes are often bound with starch, sand and fillers that clog your fire and add nothing to the heat. Good lumpwood snaps when you break it and has visible grain.

Coal: long fires, deep heat, and a learning curve

Blacksmith's coal — the bituminous sort, not household anthracite — is the traditional fuel of the trade, and it is still the best value per hour of forge time. It behaves unlike anything else, which is exactly what trips people up.

You do not simply heap coal on the fire. You build a coking fire: a core of burning coke in the middle of the firepot, surrounded by a bank of green coal. The heat drives the volatiles out of the outer coal, turning it into coke, and you push that coke inward as the core burns down. Done properly, the fire is smoky only while it establishes — perhaps ten or fifteen minutes — and then settles into a clean, ferocious heat you can hold for hours.

• Heat: the deepest and most controllable of the three, with a wide working zone.
• Clinker: the main chore. Impurities fuse into glassy lumps that block your air blast, so you need to break them out with a poker every hour or so.
• Cost: usually the cheapest per kilo, and it goes a long way because you can bank a fire and leave it overnight.
• Smoke: significant on lighting, and noticeable on gusty days if you let the green coal burn.

Coke: the clean, steady middle ground

Coke is essentially coal with the smoke already cooked out of it — the same stuff your coal fire turns into, delivered ready-made. It is the compromise fuel, and for a lot of small workshops it is the one that actually works.

It is harder to light than charcoal and needs a steady, well-managed air blast to stay at its best; starve it and it sulks. Once going, though, it burns hot, clean and remarkably consistently, with very little flame and almost no smoke. Clinker still forms, and often more stubbornly than with coal, so keep your poker handy. Coke tends to spit and spark less than coal too, which your forearms will appreciate.

Smoke, clinker and keeping the peace

Before you buy anything, check whether you are in a Smoke Control Area. These are declared under the Clean Air Act 1993 and cover much of urban Britain. In such an area you may only burn authorised smokeless fuels, and burning ordinary bituminous coal can land you with a fine. Charcoal and coke are generally acceptable, but the rules and the authorised fuel list are worth confirming with your local council rather than assuming.

Even outside a smoke control area, be a decent neighbour. Practical steps that cost nothing:

• Light the fire with charcoal or a small coke starter bed, then build up — this avoids the long smoky phase.
• Work with the wind, not against it, and keep your chimney or hood drawing properly.
• Avoid firing up at teatime on a still summer evening when everyone's windows are open.
• Never burn treated timber, plastics or household rubbish. The fumes are genuinely nasty.

Choosing for your own workshop

If you forge occasionally in a small garden, want minimal fuss and have neighbours close by, charcoal is the sensible start. It costs more per session but forgives almost everything. If you have space, a bit of distance from other houses, and you forge regularly, coal rewards the effort with cheap, long-lasting heat. If you are somewhere in between — keen, frequent, but still in town — coke is usually the answer.

Buy a small quantity of each and try them in your own firepot before committing. Store everything dry and off the ground: coal and coke in a lidded bin, charcoal in a sealed bag or box, because damp charcoal is miserable to light. The right fuel is the one that suits your fire, your budget and your postcode — and once you find it, the forge stops being a logistical problem and goes back to being a pleasure.