Complete Primitive Metallurgy and Smelting: From Rock to Metal
Extracting metal from ore is one of humanity's greatest achievements. This campaign covers ore identification, furnace construction, smelting processes, and basic casting.
Chapter 1: Ore Identification
Ore
Metal
Color
Streak
Hardness
Smelting Temp
Abundance
Hematite
Iron
Steel gray to red
Red-brown
5-6
2,200°F+
Very common
Magnetite
Iron
Black, magnetic
Black
5.5-6.5
2,200°F+
Common
Bog iron
Iron
Brown, rusty
Yellow-brown
Variable
2,200°F+
Common (wetlands)
Malachite
Copper
Green
Light green
3.5-4
2,000°F
Moderate
Azurite
Copper
Blue
Light blue
3.5-4
2,000°F
Moderate
Native copper
Copper
Copper red
Copper red
2.5-3
1,981°F (melt)
Rare
Cassiterite
Tin
Brown-black
White-light brown
6-7
1,800°F
Uncommon
Galena
Lead
Gray, metallic
Gray
2.5
1,100°F
Common
Sphalerite
Zinc
Brown-yellow
White-yellow
3.5-4
1,665°F
Common
Chapter 2: Bloomery Furnace
Bloomery furnace construction: 1) Build cylindrical shaft from clay and straw (or fire bricks). 2) Dimensions: 3-4 ft tall, 10-12 inches interior diameter. 3) Wall thickness: 3-4 inches minimum. 4) Tuyere hole: 4-6 inches from bottom (for bellows pipe). 5) Tap hole: at bottom (optional, for slag drainage). 6) Dry furnace thoroughly (weeks if possible; fire gently to cure). 7) Charge: alternate layers of charcoal and crushed ore. 8) Light charcoal at bottom. 9) Pump bellows continuously (critical: must maintain high temperature). 10) Smelt for 4-8 hours. 11) Result: bloom (spongy mass of iron mixed with slag). 12) Remove bloom, hammer while hot to expel slag. 13) Result: wrought iron (workable metal).
Component
Material
Function
Notes
Shaft
Clay + straw, or fire bricks
Contains the smelt
Must withstand 2,500°F
Tuyere
Clay pipe
Directs air into furnace
Angled slightly downward
Bellows
Leather, wood
Provides forced air
Must deliver continuous blast
Charcoal
Hardwood charcoal
Fuel and reducing agent
Must be high quality
Ore
Crushed to walnut size
Raw material
Roast first to remove moisture
Flux
Limestone or seashells
Removes impurities as slag
Optional but helpful
Chapter 3: Copper Smelting
Step
Temperature
Action
Duration
Ore roasting
500-800°F
Drive off moisture and sulfur
2-4 hours
Crushing
Room temp
Break roasted ore to pea size
30-60 min
Charging furnace
N/A
Layer charcoal and ore
15 min
Smelting
2,000-2,200°F
Bellows-driven reduction
2-4 hours
Tapping or breaking
2,000°F+
Pour or extract molten copper
Minutes
Refining
2,000°F
Re-melt to remove impurities
1-2 hours
Casting
2,000°F
Pour into molds
Minutes
Copper from malachite: 1) Crush malachite ore to pea-sized pieces. 2) Roast in open fire (drives off CO2 and water). 3) Build small furnace or use crucible in charcoal forge. 4) Layer charcoal and roasted ore in furnace. 5) Pump bellows to reach 2,000°F+. 6) Carbon from charcoal reduces copper oxide to metallic copper. 7) Copper melts and pools at bottom. 8) Tap or break furnace to retrieve copper. 9) Re-melt in crucible to refine. 10) Cast into ingots or directly into sand molds.
Chapter 4: Bronze Making
Alloy
Composition
Melting Point
Hardness
Use
Tin bronze
90% copper, 10% tin
1,750°F
Good
Tools, weapons, bells
Arsenical bronze
95% copper, 5% arsenic
1,900°F
Good
Historical (toxic to make)
Phosphor bronze
95% copper, 5% tin, trace phosphorus
1,800°F
Very good
Springs, bearings
Aluminum bronze
90% copper, 10% aluminum
1,900°F
Very good
Marine hardware
Bronze casting: 1) Melt copper in crucible (2,000°F). 2) Add tin (10% by weight) to molten copper. 3) Stir with graphite or green wood rod. 4) Skim slag from surface. 5) Pour into pre-heated mold. 6) Sand casting: pack fine sand around wax or wood pattern. 7) Lost wax: coat wax model in clay, fire to melt wax, pour bronze into void. 8) Cool slowly (rapid cooling causes cracking). 9) Break mold, clean casting. 10) Finish with filing, grinding, polishing.
Chapter 5: Charcoal Production
Wood Type
Charcoal Quality
Burn Temperature
Yield
Best For
Oak
Excellent (dense, long-burning)
Very high
20-25%
Smelting, forging
Maple
Very good
High
20-25%
Smelting, forging
Hickory
Excellent
Very high
20-25%
Smelting
Pine
Fair (light, fast-burning)
Moderate
15-20%
Starting fires, light forging
Willow
Good (very light)
Moderate
15-20%
Gunpowder, art
Bamboo
Good
Moderate-high
20-25%
General purpose
Reference Card
Charcoal is the key to metallurgy (charcoal provides both the heat and the chemical reduction needed to extract metal from ore; without charcoal, no smelting). 2. Bellows make the difference (natural draft cannot reach smelting temperatures; forced air from bellows is what makes metal extraction possible). 3. Bog iron is everywhere (iron-rich deposits in swamps and stream beds were the primary iron source for centuries; look for orange-stained water). 4. Crush the ore fine (smaller pieces expose more surface area to the reducing gases; walnut-sized for bloomery, pea-sized for crucible). 5. Roast before smelting (pre-roasting ore drives off moisture and converts carbonates/sulfides to oxides, which smelt more easily). 6. The bloom is not finished iron (the raw bloom from a bloomery is full of slag; it must be hammered extensively while hot to consolidate into usable iron). 7. Copper smelts easier than iron (copper ores reduce at lower temperatures; copper smelting is the logical first step in learning metallurgy). 8. Bronze changed the world (adding 10% tin to copper creates bronze, which is harder and casts better; this single alloy enabled civilization).
