Blacksmithing is the art and mystery of working with the black metal – iron. At ambient temperature iron is very hard. To make it plastic we heat it to almost melting so we can shape it to our needs. We use a forge to accomplish this.
Forge:
The forge is a pile of clay whose purpose is to get the fire to a height for convenient work. This forge is formed from logs to keep the clay in place. The hearth – the place that contains the fire – is made of bricks. An iron block called a tyere is used to carry the air forced from the bellows to the fire.
Fire:
A fire is made of three elements: fuel, air, and heat. The fuel we use is charcoal, the air is provided by a bellows, and the head is added by a couple of methods.
Charcoal:
Charcoal is made by stacking 4’ pieces of wood in a 30’ to 40’ circle around a triangular chimney at the center. When the first course is stacked, a second is added to make the pile around 8’ high. This is covered with damp leaves and dirt, leaving the hole at the top of the chimney open. When the pile is covered small chunks of wood are used to fill the chimney, hot coals are added and the chimney hole is closed with damp leaves and dirt. The pile smolders for a week or more during which time the impurities in the wood are burned off leaving pure carbon. The charcoal we use is purchased and is called lump charcoal or cowboy charcoal. It is the same fuel used in 1780. Anthracite or bituminous coal was not in use to any great extent in America and not at all in the backcountry.
Bellows:
You could forge iron with just a fire. The problem is that it might take 10 to 30 minutes to get the iron to forging temperature. That is why we use the bellows to add air to the fire to get the iron to temperature faster. Our bellows is double chambered. We pump the bottom chamber which has a flap valve on the bottom board to allow air in and a flap valve at the top to allow the air to fill the top chamber. By keeping the top chamber from collapsing all the way, we keep a constant air flow to the fire in the forge.
Fire:
Starting the fire is made easier by having the bellows to blow air to increase the fire. I like to start the fire by adding a shovel of hot coals from another fire. This is covered with charcoal and the bellows pumped. This method starts a good fire quickly. You can also build a small wood fire and light it with flint and steel. When this wood is started, cover it with charcoal and pump the bellows.
Tools:
The primary tool is the anvil. 17th century anvils had no horn and were not mounted so the anvil could be turned to use all its facets. 18th century anvils are denoted by their broad face and small horn. They are mounted to keep them stable during work. The other primary tool is the hammer. Hammers come in a variety of styles with the weight determined by the amount of iron you need to move. The basic hammer is the cross peen with the peen either horizontal or vertical. Tongs are our burn free hands. They also come in a large variety for different purposes – you simply use the pair that helps you get the job done the easiest. The anvil has a square hole called the hardy hole which takes a cut off tool called a hardy. This is essential for making nails. There are a variety of handled tools besides hammers. These include hot cutters for slitting and cutting off, flatters for flattening work, set hammers for getting folds tight (as in making hinges), headers for nails and bolts, fullers for drawing material in only one direction, and swages for shaping material. One very helpful tool is the swage block. This is a block of iron cast with many different shapes on it into which metal may be hammered to take that shape. Ladles, spoons, skimmers, and even octagonal rifle barrels would be very hard to shape without the swage block.
Iron:
The iron used in 1780 was wrought iron. Wrought means hammered – William Hill had a hammer mill at his iron furnace. This means that he made wrought iron as well as cast iron. Cast iron is brittle and is molded into objects such as pot, kettles, fire backs, cannon, and shot for cannons. Wrought iron has some of the flux – a silicon glass material – added back into the iron. As the iron is hammered it is drawn out (see below) and develops a grain structure like wood. If you hit a cast iron pot with a hammer, it will shatter at room temperature with a grainy edge where it is broken. If you hit wrought iron with a hammer it is tough and will not break. True wrought iron is almost impossible to find today. What we use is mild steel – low carbon steel. Higher carbon steel is hard to forge – that is move with a hammer when heated to forging temperature. The stock we use should be square or rectangular in cross section. This is because early iron works did not have the rolls to make round stock. Flat rollers can make many sizes of flat / rectangular or square bars. The other set of rolls common to an iron works of the period were the slitting rolls. The wrought iron was rolled flat to about a quarter of an inch. When it was heated and run through the slitting rolls they slit the flat bar into many bars ¼” by ¼“ square. This was nail stock or nail rod. Other thicknesses were made depending on the sizes of the slitting rolls the iron works had. All rolling in these mills was done with the iron heated. The rolls were turned by water wheels with one wheel turning the top roll and one wheel turning the bottom wheel. Round stock is not appropriate to work in a forge in the 1780’s backcountry. Round stock was made from square by forging and filing.
Basic Methods:
There are several basic processes that when stringed together can forge anything. The basic process is drawing out. If you hammer on a piece of hot iron, you squish it. This causes the iron to get thinner but it also makes it longer. If you turn it 90 degrees and hit it again you can keep the square shape but make the bar thinner and longer. This is drawing out. You can even taper the rod to a very sharp point. The opposite of drawing out is upsetting. This is heating the end of the bar and hammering on the end or pounding the end of the bar on the anvil. This makes the bar thicker and shorter. Forge welding is accomplished by hammering short, slight tapers on two bars. They are then heated to a sparking white heat, quickly laid on top of each other on the anvil, and hammered rapidly to force the almost melted metal together, causing a welded joint. Splitting a bar is done by first placing a piece of sheet metal on the anvil to protect it. A handled hot cutter is used with the hammer to cut the metal in half. This is used to make the two tines on a fork or to start the hole in the round handle of a turn screw. Fullering is to hit the hot metal with the cross peen or with a fuller to draw out the metal in one direction, making a thin, wider piece of metal. This is used for making scrapers (spatulas) or dippers. Swaging or die work is to use a shaped form to shape the work when it is hot.
Temperatures:
Josiah Wedgwood, the pottery maker, learned from looking in kilns that all matter glows the same color at the same temperature. One use of this is that you can’t get a piece of iron yellow hot with a red hot fire! The following are the approximate temperatures of the various colors:
White welding heat (sparking) – 2500 degrees
Yellow heat – 2300 degrees
Dark yellow – 2100 degrees
Light cherry red -1700 degrees
Medium cherry red – 1500 degrees
Cherry red – 1300 degrees
Dark cherry red (blood red) – 1200 degrees
Dull red glow – 1100 degrees
No color – up to 1000 degrees
Judging temperatures is affected by the ambient light. The more light, the lower the temperature appears. The less ambient light the more truly temperature is judged. As you can see, a dark piece of iron can be up to 1000 degrees. Be careful picking up anything in a blacksmith shop.
Slack Tub:
This is the tub of water used for cooling and hardening iron. Plunging carbon steel in a tub of water and cooling it rapidly makes it harder.
Annealing:
Placing a piece of hot iron in a bucket of sand or ashes and allowing it to cool slowly anneals or softens the iron. Allowing it to cool in the air without quenching it in water or oil will cause it to be somewhat softer.
Blacksmithing is part science and part art. It can only be learned by doing – practice, practice, practice.