How to forge metal in the wild – building a forge (foundry) from clay
If modern civilization fails, one of the first pieces of equipment required to bring mankind back from the stone age will be the means to forge and form metal tools. To do this requires a forge or a foundry. A forge provides the means to heat metal so it can be shaped. A foundry provides the means to melt metal so it can be formed into predefined shapes using a mold.
In either a forge or foundry, charcoal can be used as fuel and placed inside a fireplace that allows the fire to be controlled through the use of a fan or bellows to introduce additional air. Pumping air into the fire causes it to consume more fuel and burn hotter (and cleaner) – hot enough to melt metal.
Creating a forge in the wilderness
In a survival situation, a forge and fan housing can be constructed using mud or clay and a rotary fan constructed using wood. The rotary fan can be operating using a bow, similar to a bow drill, to generate high rpms needed to force air into the fire.
Create the rotary fan
To create the fan blades, find two flat pieces of flat wood about 6-8 inches long. Notch both pieces in the middle so they can be fit together (in the notch) to form a crosshatch or X-shape. The notch will allow the pieces to fit together so the blade edges are even on the top and bottom. The resulting structure is our fan blade.
Notch the bottom of a long, sturdy stick and fit it around the notched section of the fan blade. Tie off the stick, above and below the fan blade, in order to tighten the stick around the fan blade. The stick will become our rotor handle. Grasping the stick in the palms of your hands, rub your palms together to cause the fan blade to spin. A notched piece of wood, a sprocket, may be placed under the blade-end of the stick to provide a stable pivot point.
Create the fan housing
The fan housing will be created from clay then turned upside down over the fan blades and the rotary stick extending through a hole in the fan housing.
Form a round bowl from clay with one end elongated to form a spout. The diameter of the bowel should be sufficient to allow the fan blades to spin within without touching the edges. Clay bowels can be formed by rolling clay into a “rope” and stacking ringed “ropes” on top of each other.
Punch a three-inch hole in the middle of the bowel to allow the rotary fan handle to extend through.
The fan housing will resemble a flat pot with a half-moon-shaped spout (and a large hole in the middle). Place an appropriate sized round branch into the spout to hold its shape. Form clay around the branch to create a fully enclosed tube for the spout.
Place the fan housing near a fire to harden the clay.
Install rotary blade in fan housing
Turn the fan housing upside down. Place the cross-hatched wood fan blade under the bowl with the rotary handle extending upward through the hole. You can now spin the fan blade, which is underneath (or inside) the fan housing, by rubbing the rotary handle between your palms. Air will be sucked through the top hole (where the stick is inserted) and blown out the spout tube. Place the tube near a fire and you will see a pronounced effect when air is pumped into the fire using the fan housing and rotary fan.
Create extension tube
Next we need an extension tube so the blower fan can be situated away from the heat of the fire. We could have simply made the spout longer but this part will extend into the fire and thus, it tends to crack and chip over time. Using a separate extension tube will allow this piece to be easily replaced when needed.
Create the tube by forming clay around a log. The diameter of the log should be slightly larger than our spout so the tube can be fitted over the spout. The tube should be a sufficient length to allow the blower fan to be placed safely away from the fire. Fire harden the clay extension.
Install extension tube into fire
Fit the extension over the fan housing spout and place the other end of the extension under your fire (or build a fire over the extension). This will let us blow air directly under the fire.
Create the furnace
Finally, create the furnace. Form clay into a 1-2-foot-wide round “oven”. Leave space at the bottom through which we can insert the blower tube.
To make a clay bowel, roll clay into tubes and form rings, stacked on top of each other, smoothing clay between the rings to form a solid, smooth surface.
Optional: Build blower fan frame
A frame can be built above the fan housing and used to anchor the fan stick in place. Using principles and operation similar to that of a bow drill, you can use a bow to turn the stick rather than spinning it in your hands.
Operating the clay forge
Fill the furnace with charcoal wood. Burn the wood, continually replenishing as the fuel burns off.
Scrap metal can be forged in the furnace. If metal is not available, we can gather iron oxide from iron bacteria deposits.
Iron bacteria derive the energy they need to survive by oxidizing rocks and minerals rich in iron. This leaves ferric oxide, a rust-like substance which acts as the main source of iron for the steel industry. In the wild, iron bacteria form around seeping river banks or the shores of lakes and ponds. It appears as a brownish orange gelatinous slime. Often times it will be found near areas where an oil-like sheen lays on top of the water.
Charcoal (carbon) chemically reacts with ferric oxide to remove the oxygen from the metal oxide leaving only the metal. When added to ferric oxide, it reduces it to pure iron.
Wood ash, made mostly of calcium carbonate and a small amount of potash and phosphate, can be used as flux. Flux, used in ceramics and metallurgy, is a substance used to reduce the melting points as well as absorbing impurities and adding desirable trace elements. Added to ferric oxide, wood ash reduces the melting point and strengthens the resulting metal.
Gather iron bacteria (iron oxide) and mix with charcoal powder and wood ash to form a clay-like substance. Shaped as required – this will act as our ingot.
Place the ingot in your furnace and fire until it melts. Shaped as needed.
Primitive Technology YouTube channel has a video illustrating the entire process along with videos demonstrating how to build huts, weapons, and tools in the wild. Great channel. Check it out.