Complete Primitive Forge and Bellows Construction: From Clay to Iron Heat
A forge is the heart of metalworking. This campaign covers forge types, bellows construction, fire management, and achieving working temperatures for iron and steel.
Chapter 1: Forge Types
Forge Type
Max Temperature
Difficulty
Materials
Best For
Ground forge (bowl)
2,000°F+
Very low
Hole in ground, clay lining
Emergency, temporary
Side-blast forge
2,200°F+
Low
Clay/brick, tuyere pipe
General blacksmithing
Bottom-blast forge
2,400°F+
Moderate
Clay/brick, tuyere from below
Heavy forging, welding
Brick forge (permanent)
2,400°F+
Moderate
Firebrick, mortar, steel
Permanent shop
Japanese-style box bellows
2,200°F+
Moderate
Wood, leather, clay
Blade smithing
Side-blast forge construction: 1) Build fire pot: clay-lined bowl or firebrick box (12-18 inches across, 6-8 inches deep). 2) Tuyere: pipe entering from the side at bottom of fire pot (1-1.5 inch diameter). 3) Tuyere material: steel pipe, clay pipe, or copper pipe. 4) Tuyere angle: slightly upward (prevents ash from clogging). 5) Connect tuyere to bellows via pipe. 6) Ash dump: removable plug or door below fire pot. 7) Work surface: flat area around fire pot for tools and stock. 8) Height: 30-36 inches (comfortable standing height). 9) Hood/chimney: optional but recommended for indoor use. 10) Quench trough: water container within arm's reach.
Chapter 2: Bellows Construction
Bellows Type
Air Output
Difficulty
Materials
Continuous Air
Mouth blowing (blowpipe)
Very low
None
Tube
No (intermittent)
Bag bellows (skin bag)
Low-moderate
Low
Animal skin, nozzle
No (intermittent)
Single-action bellows
Moderate
Moderate
Wood, leather, nails
No (air on squeeze only)
Double-action bellows
High
Moderate-high
Wood, leather, valves
Yes (air on push and pull)
Box bellows (piston)
High
Moderate
Wood, piston, valves
Yes (continuous)
Hand-crank blower
Very high
High
Metal gears, fan
Yes (continuous)
Double-action bellows: 1) Two chambers share a common nozzle. 2) When top chamber compresses, it pushes air out nozzle. 3) Simultaneously, bottom chamber expands, drawing in fresh air. 4) When top chamber expands, bottom compresses. 5) Result: continuous airflow regardless of handle direction. 6) Construction: two hinged boards per chamber, leather sides. 7) Each chamber has an intake valve (flap that opens inward only). 8) Both chambers connect to single output pipe (nozzle). 9) Handle operates both chambers in opposition. 10) Size: 18-24 inches long for blacksmithing. 11) Leather must be supple (oil regularly). 12) Valves must seal well (air leaks reduce efficiency).
Chapter 3: Fire Management
Temperature
Color
Use
Fuel Needed
400-500°F
No visible color
Tempering
Light fire
900-1,000°F
Faint red (dark)
Annealing
Moderate fire
1,100-1,200°F
Cherry red
Forging (easy bending)
Good fire
1,400-1,500°F
Bright cherry to orange
Forging (heavy work)
Hot fire
1,700-1,800°F
Light orange to yellow
Forging (maximum workability)
Very hot fire
2,000-2,100°F
Light yellow to white
Forge welding (iron)
Maximum fire
2,300°F+
White, sparking
Forge welding (steel), burning
Extreme (risk of burning steel)
Fire management principles: 1) Build fire with charcoal (not wood; charcoal burns hotter and cleaner). 2) Bank fire: pile charcoal around and over the work piece. 3) Air blast from bellows heats the fire zone directly above the tuyere. 4) More air = hotter fire (up to a point; too much air cools by excess). 5) Clinker: fused ash that blocks airflow; remove regularly. 6) Fire size: match to work piece (small work = small fire). 7) Deep fire for even heating (bury work piece in charcoal). 8) Shallow fire for localized heating (expose only the area to be worked). 9) Oxidizing fire: excess air, burns carbon from steel surface. 10) Reducing fire: limited air, protects steel from carbon loss.
Chapter 4: Anvil and Tools
Tool
Function
Material
Priority
Anvil (or substitute)
Work surface for hammering
Steel, large rock, railroad track
Essential
Hammer (2-3 lbs)
Primary forging tool
Steel head, wood handle
Essential
Tongs (various)
Hold hot metal
Steel
Essential
Hardy (cutting tool)
Cut hot metal
Steel, fits in anvil hardy hole
Very important
Punch
Make holes in hot metal
Steel rod
Very important
Chisel (hot cut)
Cut hot metal
Steel
Very important
Wire brush
Clean scale from metal
Steel wire
Important
Quench bucket
Cool metal, harden steel
Water or oil in metal bucket
Essential
Chapter 5: First Projects
Project
Skills Practiced
Difficulty
Time
Steel Needed
S-hook
Drawing out, bending, scrolling
Very low
15-30 min
1/4 inch round, 8 inches
Nail
Drawing to a point, heading
Low
10-20 min
1/4 inch square, 4 inches
J-hook
Bending, tapering, punching
Low
20-30 min
3/8 inch round, 10 inches
Bottle opener
Flattening, punching, bending
Low-moderate
30-45 min
3/8 inch round, 8 inches
Knife (simple)
Drawing, tapering, grinding, heat treat
Moderate
2-4 hours
Flat bar or old file
Tongs
Drawing, bending, riveting
Moderate-high
2-4 hours
1/2 inch round, 18 inches x2
Fire poker
Drawing, bending, scrolling
Low
30-60 min
3/8 inch round, 30 inches
Reference Card
Charcoal is the only proper forge fuel (wood does not burn hot enough for ironwork; charcoal reaches the temperatures needed for forging and welding). 2. Air makes the heat (the bellows is as important as the forge itself; without forced air, charcoal cannot reach forging temperature). 3. Double-action bellows provide continuous air (a single-action bellows only blows on the squeeze; double-action provides air on both push and pull). 4. Color tells temperature (learn to read heat colors in dim light; cherry red is forging heat, yellow-white is welding heat). 5. Remove clinker regularly (fused ash blocks airflow and creates cold spots; clean the fire pot between heats). 6. The anvil is the second most important tool (after the hammer; any heavy, flat, hard surface works as an anvil in a pinch). 7. Start with S-hooks (the S-hook teaches drawing out, bending, and scrolling; make fifty before moving to harder projects). 8. Quench within reach (hot metal must be cooled quickly for hardening; keep the quench bucket within arm's reach of the anvil).
