Smelting Ore into Useful Metal

Smelting ore dug up from the earth is a very important step before that metal can be used. Smelting removes many of the impurities of the metal and converts much of it into the crystalline structure for which it is sought. Smelting metal is a hard laborious task which requires the work of highly skilled professional smelters. It also requires expensive smelting furnaces as well as a considerable amount of fuel.


Background Information

Smelting Iron and Steel

Before iron can be worked into useful products, it must first be refined from iron ore. This process is called "smelting". First, the iron ore is crushed with a hammer into gravel, with the largest bits no larger then corn kernels. Next, something called a "flux" is needed. When iron is exposed to the air in the atmosphere for too long, it rusts (oxidizes). When the iron ore is crushed into small bits, it has more surface space and oxidizes (rusts) at an accelerated rate. Heating of the iron ore during smelting also increases the rate of oxidation. A flux is a material mixed in with the crushed iron ore during melting, which blankets it from exposure to the air. Flux also needs to be a material with will envelop the melting iron ore, but not intermix with it. The iron ore and the flux will intermingle like oil and water, The flux will coat the melting ore, but can easily be drained off and separate from it later. The most common flux is crushed limestone. It's a very common material, crushes easily, which melts and separates appropriately. To start the smelting process, the crushed iron ore is poured into a crucible, followed by the crushed limestone flux which should cover it completely. The crucible itself is generally a pottery ceramic vessel which can stand up to intense heat, melting it's contents and yet remaining solid. The melting process in a medieval furnace takes about 12 hours. Once the melting process is over, both the iron ore and limestone flux can be poured out. The melted limestone remains more thin, liquid and even frothy for a longer period of time. The iron tends to coagulate as a more substantial mass. Because of this, the iron can be scooped up and the liquid limestone flux will simply drip off (also forming a very thin coating on the iron with later protects it from rust). The resulting iron is often hammered or molded into simple rectangle shaped ingots for storage or transport.

Smelting iron and steel is a real pain in the ass with medieval technology. There are three general categories of iron once it has been heated and made useful from ore. These are Cast Iron, Wrought Iron, and Steel. Burring wood, you can only get a temperature of 700 degrees which allows only the creation of Wrought Iron. If you use charcoal, you can get a temperature as high as 1200 degrees which allows for the melting of the Iron. When this happens it gets various amounts of Carbon in it from the smelting process. Here is the problem though; controlling how much Carbon gets in during medieval smelting is a practical impossibility. Sometimes it gets a small amount of Carbon and comes out as a sludge of Wrought Iron. Sometimes it gets just enough Carbon to come out as Steel. Other times it gets a lot of Carbon and comes out as Liquid Cast Iron that can only be poured immediately and can be worked no further after this casting.

Choosing to make Wrought Iron by only heating to about 700 degrees is a simple matter. Choosing to liquefy the Iron and make sure it gets a lot of carbon resulting in Cast Iron is also simple. Making steel, the balanced middle, is very hard.

Medieval smelters who desired to make steel did something very ingenious. Rather than having a special smelting furnace, they made three different types of smelting furnace. The first was the normal heat furnace that would burn charcoal or wood and would smelt iron. A second was an "oxygen-rich furnace" to try to decarburize or reduce the carbon content of cast iron. The third was a "carbon-rich furnace" to increase carbon levels in liquid Wrought Iron. Often the same Iron has to be jostled back and forth between the different smelting furnaces to balance the carbon content and produce steel.

In the long run what does this really mean for game mechanics. Making steel rather than Wrought Iron or Cast Iron requires a far more advanced facility with specialized furnaces, burns a lot more fuel per unit, is much slower to make and requires a more experienced smelter. Details will be described later


Basics

Producing useful metal requires five different things in this system. Here is a brief summary of each.

Ore- Metal ore is produces through mining and is discussed in that section. Generally it takes 2 units of ore to produce 1 unit of pure metal. Because the "grade" of metal found in rock is never as high as 100%, it often requires the mining of many units of rock to produce one unit of metal ore.

Smelters- Smelters are the workers who know how to use heat to smelt down ore. How much work a smelter can do is represented in "OSUs", or Ore Smelting Units.

Tools- Smelters must be provided with adequate tool to do their work effectively.

Facilities- For smelters to do their work, they need to have an adequate building or buildings. Pains should be made to make the building as fireproof as possible. Burning embers are common and a thatch roof or thresh floor will be set aflame in days.

Furnaces- The use of a furnace is absolutely essential to the smelting of ore into useful metal. A furnace can only do so much in a given time. How much metal can be smelted is represented in "FCUs", or Furnace Capacity Units.

Fuel- Smelting metals requires a lot of fuel to keep the furnaces burning. Fire wood, coal and charcoal are the fuels normally used. Some metals require better fuels for hotter flames.


Smelters

Smelters are skilled individuals who know how to apply heat and other techniques to produce usable metals from raw metal ore. From the very time metals were discovered, they are valued. Once people saw how they could be used, they became indispensable. Those who know how to work metals became highly regarded. In many primitive societies, smelters and smiths were seen as practitioners of magic and even as magical or divine beings themselves. Though some metals like lead melt down with some ease, balancing the carbon levels to make steel is a work requiring great skill. In our system, the most important thing to know about any smelter working is his rank. Rank represents level of skill and efficiency. Higher ranked smelters can smelt more metal in the same amount of time as well as smelt more difficult metals. How much work a smelter can do is represented in "OSUs" or Ore Smelting Units. The table to the right denotes how many OSUs smelters of various ranks generate.

Rank of Smelter

OSUs in a month

New

200

Poor

250

Adept

300

Master

350

Grand Master

400


Building and Outfitting a Smelter's Facility

Building - The first thing you will need is a building. Nothing disrupts a furnace that needs to stay at a specific temperature like changing weather. Just about any type of building will do, but you must have at least 40 square foot per smelter working there. Also an eye to fire safety is important.

Furnaces- You will need one or more smelting furnaces. Rules for constructing them can be found below. Furnaces provide "FCUs", or Furnace Capacity Units. You can only do so much smelting in a month as your furnace capacity will allow regardless of how many smelters you have working.

Tools- Lastly a Smelter will need Smelters Tools. These include several simple tools such as tongs, hooks, hammers and bellows. These can be made by a tool smith.

Crucible- Crucibles are the containers the ore is actually melted in. One Crucible will be needed for each Smelter. Crucibles can be made by Potters or Bellsmiths.


Smelting Furnaces

FCUs- A factor of serious consideration when smelting ore is how much capacity your furnaces can handle. This is represented in FCUs, or Furnace Capacity Units. A furnace produces 500 a month. Note that smelting furnaces are far less efficient in terms of volume and fuel consumption than pottery and mortar making kilns.

Standard Furnace- Most metals require only a standard furnace to smelt down metals within them. This furnace can burn wood, coal or charcoal as fuel. Operating a furnace consumes about 500 units of coal or charcoal (1000 of fire wood) per month of continuous use. A standard furnace can provide a maximum of 500 FCUs per month. Each FCU utilized requires 1 unit of coal or charcoal (or 2 fire wood). Constructing a standard furnace requires 50 units of masonry brick, clay brick or flagstone, 10 units of mortar and 20 hours of labor from a mason of at least adept rank.

Steel Furnaces- Unlike smelting other metals, smelting steel requires a standard furnace, an "oxygen-rich furnace" and a "carbon-rich furnace". This three furnace setup requires 150 units of masonry brick, clay brick or flagstone, 30 units of mortar and 100 hours of labor by masons of at least master rank and directed by an engineer of at least adept rank. When making steel all three furnaces must be active because the ore is switched back and forth between the three. A steel furnace can provide a maximum of 500 FCUs per month. Each FCU utilized requires 3 units of charcoal.


Ingot Production Table

Product

Notes

OSUs Required

Materials Required

Fuel Consumed

FCUs Required

Smelter Rank Required

Smelting Furnace Needed

Unit of

Lead Ingots

Soft, easy to work, quick to smelt

30 OSUs

2 units of Lead ore

50 units of Coal or Charcoal (or 100 units of Firewood)

50 FCUs

New

Standard Furnace

Unit of

Tin Ingots

Soft, easy to work, not very strong.

45 OSUs

2 units of Tin ore

50 units of Coal or Charcoal (or 100 units of Firewood)

50 FCUs

Poor

Standard Furnace

Unit of

Copper Ingots

First tool metal, strongest that can be smelted with firewood

60 OSUs

2 units of Copper ore

100 units of Coal or Charcoal (or 200 units of Firewood)

100 FCUs

Poor

Standard Furnace

Unit of

Nickel Ingots

Hard & brittle

60 OSUs

2 units of Nickel ore

100 units of Charcoal

100 FCUs

Adept

Standard Furnace

Unit of "Wrought"

Iron Ingots

The best natural tool metal that is not an alloy.

60 OSUs

2 units of Iron ore

100 units of Coal or Charcoal

100 FCUs

Adept

Standard Furnace

Unit of

Silver Ingots

Precious metal

75 OSUs

1 unit of Silver ore

100 units of Coal or Charcoal

100 FCUs

Adept

Standard Furnace

Unit of

Gold Ingots

Precious metal

90 OSUs

1 unit of Gold ore

50 units of Coal or Charcoal (or 100 units of Firewood)

50 FCUs

Adept

Standard Furnace

Unit of

Platinum Ingots

Precious metal, very rare, very hard to mine and smelt

100 OSUs

1 unit of Platinum ore

200 units of Charcoal

200 FCUs

Adept

Standard Furnace

Unit of

Brass Ingots

Ornamental alloy

100 OSUs

1 unit of Copper ore

1 unit of Zinc ore

100 units of Coal or Charcoal

100 FCUs

Adept

Standard Furnace

Unit of

Bronze Ingots

Fairly strong alloy. Stronger then copper and can still be made with firewood.

100 OSUs

1 unit of Copper ore

1 unit of Tin ore

100 units of Coal or Charcoal (or 100 units of Firewood)

100 FCUs

Adept

Standard Furnace

Unit of

Steel Ingots

Very strong, best tool metal of the historic period.

120 OSUs

2 units of Iron ore

300 units of Charcoal

100 FCUs

Master

Steel Furnaces


Partial Metal Units

This system uses a standard of 1 cubic foot as the normal unit size for most materials. Though this remains the case for metal ingots and ore, we allow the processing of smaller fractions of one unit with particularly rare metals because of the unlikelihood and impracticality of expecting an entire cubic ft of rare metals like platinum or gold. When dealing with precious metal ore, simply round up to the nearest whole unit in terms of how many FCUs, fuel and OSUs are needed.


Why do ingots of the same size require varying FCUs?

Because some take longer to melt in the furnace. FCUs represent volume multiplied by time.


Example

The town of Calderon has two smelters, one adept and one master which are represented by 650 OSUs produced per month. The town has three standard furnaces which provide a maximum of 1500 FCUs monthly. This month the town produces 30 units of copper ore which the smelters want to turn onto copper ingots. One unit of copper ingots requires 2 units of copper ore, 60 OSUs, 100 FCUs and 100 units of coal as fuel. 30 units of copper ore is enough to make 15 units of copper ingots, but the smelter's 650 OSUs limit them to producing 10 units of copper ingots ( 10 x 60 OSEs = 600 OSUs). The 1000 FCUs needed for the 10 units of copper ingots are well within what the town's furnaces are capable of. The smelters go to work, converting 20 units of copper ore into 10 units of copper ingots expending 1000 units of coal in the process. Ten units of copper ore sit, perhaps to be smelted next month, if the miners mine less ore, or the smelters get more help.