Campaign 135: Pour the Metal
The Complete Metal Casting, Foundry Work, and Mold Making Guide
A Sovereignty Module of the Practitioner Community
Preamble
Casting is the process of pouring molten metal into a mold to create a solid object. It is one of the oldest manufacturing processes, dating back over 6,000 years. Casting produces objects that cannot be made by forging: complex shapes, hollow forms, precise replicas, and large components. A backyard foundry capable of melting aluminum, bronze, or iron can be built from common materials for minimal cost. With casting, you can produce tools, hardware, machine parts, cookware, weapons, and decorative items from scrap metal. This campaign covers the complete foundry process from furnace construction through pattern making, mold making, melting, pouring, and finishing.
Part I: Foundry Construction
Chapter 1: Backyard Furnace Types
| Furnace Type | Fuel | Max Temperature | Metals | Complexity | Cost |
|---|---|---|---|---|---|
| Charcoal crucible furnace | Charcoal + forced air | 2,000°F (1,100°C) | Aluminum, zinc, lead, pewter | Simple | Low ($20-50 in materials) |
| Propane crucible furnace | Propane + forced air | 2,200°F (1,200°C) | Aluminum, bronze, brass | Moderate | Moderate ($50-100) |
| Waste oil furnace | Used motor oil + forced air | 2,500°F (1,370°C) | Aluminum, bronze, brass, cast iron | Moderate | Low (free fuel) |
| Coke/coal furnace | Coke or coal + forced air | 2,800°F+ (1,540°C+) | Cast iron, steel (with flux) | Advanced | Moderate |
| Electric furnace | Electricity (resistance or induction) | Variable | Any metal | Advanced | High |
Chapter 2: Building a Simple Charcoal Furnace
| Component | Material | Details |
|---|---|---|
| Body | Steel bucket, drum, or pipe (12-18" diameter) | Lined with refractory material |
| Lining | Refractory cement, or mix: 50% sand + 50% plaster of Paris | 2-3 inches thick, dried thoroughly before first use |
| Air supply | Hair dryer, shop vac, or hand-cranked blower | Connected to tuyere (air inlet pipe) |
| Tuyere | Steel pipe (1-2" diameter) entering furnace near bottom | Angled slightly downward to prevent metal flowing back |
| Lid | Refractory-lined steel plate with hole for crucible access | Retains heat, improves efficiency |
| Crucible | Steel pipe (capped), cast iron pot, or commercial graphite crucible | Must withstand metal's melting point + 200°F margin |
| Base | Fire bricks or concrete block | Elevate furnace off ground, provide stable platform |
Chapter 3: Melting Points of Common Metals
| Metal | Melting Point | Casting Temp | Availability | Scrap Sources |
|---|---|---|---|---|
| Lead | 621°F (327°C) | 700°F | Easy | Wheel weights, old pipes, fishing sinkers |
| Tin | 449°F (232°C) | 550°F | Moderate | Solder, tin cans (plating only) |
| Zinc | 787°F (420°C) | 900°F | Easy | Die-cast parts, pennies (post-1982) |
| Aluminum | 1,221°F (660°C) | 1,350°F | Very easy | Cans, engine parts, cookware, wheels |
| Brass | 1,700°F (930°C) | 1,900°F | Moderate | Plumbing fittings, shell casings, hardware |
| Bronze | 1,742°F (950°C) | 1,950°F | Moderate | Bearings, bushings, statues |
| Copper | 1,984°F (1,085°C) | 2,100°F | Moderate | Wire, plumbing, electrical components |
| Cast iron | 2,200°F (1,204°C) | 2,400°F | Advanced | Engine blocks, brake drums, pipe |
Part II: Pattern and Mold Making
Chapter 4: Pattern Making
| Material | Durability | Detail | Use |
|---|---|---|---|
| Wood | Good (multiple uses) | Good | Most common pattern material. Carve or turn to shape. |
| Foam (polystyrene) | Single use (burns out) | Excellent | Lost-foam casting. Pattern vaporizes when metal is poured. |
| Wax | Single use (melts out) | Excellent | Lost-wax (investment) casting. Finest detail possible. |
| 3D printed (PLA) | Single use (burns out) | Excellent | Modern lost-pattern casting |
| Metal (master pattern) | Permanent | Good | Production runs of identical parts |
| Clay/plaster | Moderate | Good | Sculpted patterns, artistic work |
Chapter 5: Sand Casting (Most Common Method)
| Step | Action | Details |
|---|---|---|
| 1. Prepare green sand | Mix: 85% fine sand + 10% bentonite clay + 5% water | Should hold shape when squeezed but crumble when poked |
| 2. Place pattern in flask (drag) | Set pattern on flat board, place bottom flask (drag) around it | Pattern is the object you want to cast |
| 3. Pack sand around pattern | Ram sand firmly around pattern, filling drag completely | Pack tight but don't crush pattern |
| 4. Flip drag | Turn drag over so pattern faces up | Flat board is now on top |
| 5. Place cope (top flask) | Set top flask on drag, aligned with pins | Dust parting powder (talc) on joint surface |
| 6. Cut sprue and riser | Place sprue pin (for pouring) and riser pin (for air escape) | Sprue: where metal enters. Riser: where air exits. |
| 7. Pack cope | Ram sand into cope around pattern and pins | Same density as drag |
| 8. Remove cope | Carefully lift cope straight up | Reveals pattern in sand |
| 9. Remove pattern | Carefully extract pattern from sand | Leave clean cavity |
| 10. Cut gates | Carve channels connecting sprue to cavity | Metal flows through gates to fill mold |
| 11. Reassemble | Place cope back on drag, aligned | Mold is ready for pouring |
| 12. Pour metal | Pour molten metal steadily into sprue until riser fills | Continuous pour, no hesitation |
| 13. Cool | Allow to cool completely before breaking mold | Aluminum: 15-30 min. Bronze: 30-60 min. Iron: 1-2 hours. |
| 14. Break out | Break sand away from casting | Sand can be reconditioned and reused |
| 15. Finish | Cut off sprue, riser, and gates. File, grind, polish. | Casting is complete |
Chapter 6: Lost-Foam Casting
| Step | Action | Details |
|---|---|---|
| 1. Carve foam pattern | Shape polystyrene foam into desired object | Hot wire cutter or knife. Include sprue attached to pattern. |
| 2. Coat pattern (optional) | Brush on refractory wash for smoother surface | Thin slurry of plaster or refractory cement |
| 3. Place in sand | Bury foam pattern in dry, unbonded sand in container | Vibrate container to settle sand around pattern |
| 4. Pour metal directly onto foam | Metal vaporizes foam and fills the space | Foam burns away, metal takes its place |
| 5. Cool and extract | Wait for cooling, dig out casting | No mold to assemble or disassemble |
ADVANTAGE: Lost-foam casting eliminates the need for a two-part mold, parting lines, and draft angles. The foam pattern IS the mold. Any shape that can be carved in foam can be cast in metal.
Part III: Pouring and Safety
Chapter 7: Safety Equipment
| Equipment | Purpose | Required? |
|---|---|---|
| Face shield (full) | Protects face from splashes and radiant heat | MANDATORY |
| Leather gloves (long cuff) | Protects hands and forearms | MANDATORY |
| Leather apron | Protects torso and legs | MANDATORY |
| Leather boots (no laces) | Protects feet. Slip-on so molten metal can't pool in laces. | MANDATORY |
| Long pants (no cuffs) | No cuffs where metal can collect | MANDATORY |
| Safety glasses (under face shield) | Backup eye protection | Recommended |
| Fire extinguisher | Emergency fire suppression | MANDATORY (nearby) |
Chapter 8: Pouring Procedure
| Step | Action | Critical Safety Notes |
|---|---|---|
| 1. Preheat mold | Warm mold with torch or in oven | Cold mold + hot metal = steam explosion risk |
| 2. Ensure dry conditions | All tools, molds, and surfaces must be BONE DRY | ANY moisture near molten metal = steam explosion |
| 3. Skim dross | Remove floating impurities from molten metal surface | Use steel skimmer |
| 4. Lift crucible | Use proper tongs/lifting device rated for weight | Secure grip, balanced load |
| 5. Pour steadily | Continuous, steady stream into sprue | Do not hesitate or stop mid-pour |
| 6. Fill riser | Pour until metal appears in riser | Confirms mold is full |
| 7. Set down crucible | Return crucible to furnace or safe surface | Never set on wet or cold concrete |
CRITICAL SAFETY: MOISTURE IS THE ENEMY. A single drop of water trapped under molten metal flashes to steam instantly, expanding 1,600 times in volume. This causes a violent steam explosion that throws molten metal in all directions. EVERYTHING near molten metal must be completely dry. No exceptions.
Part IV: The Practitioner Foundry Reference Card
DRY EVERYTHING: The single most important safety rule in foundry work. Moisture + molten metal = steam explosion. Tools, molds, crucibles, ground surface — everything must be bone dry.
START WITH ALUMINUM: Aluminum melts at 1,221°F, well within range of a charcoal furnace. Scrap aluminum is everywhere (cans, cookware, engine parts). Master aluminum casting before attempting higher-melting metals.
GREEN SAND IS REUSABLE: The sand mold material (85% sand + 10% bentonite clay + 5% water) can be broken up, re-moistened, and reused indefinitely. One batch of green sand serves for hundreds of castings.
LOST-FOAM IS THE EASIEST METHOD: Carve your pattern in polystyrene foam, bury in dry sand, pour metal directly onto foam. The foam vaporizes and metal fills the space. No two-part mold, no parting line, no draft angles.
FULL PPE ALWAYS: Face shield, leather gloves, leather apron, leather boots (slip-on, no laces), long pants (no cuffs). Molten metal splashes are inevitable. Dress for them.
REMEMBER: Casting is the technology that built the Bronze Age and the Iron Age. It produces objects that cannot be made by any other method: complex shapes, hollow forms, machine parts, and tools. A Practitioner with a backyard furnace and green sand can produce hardware, cookware, tools, and machine parts from scrap metal. This is manufacturing sovereignty — the ability to make what you need from what you have.
Council Approval
Council Result: 12/12 APPROVED.