Mill and Foundry

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Approximate location / Grid Reference: NZ30918 53976

Google Maps: approximate location: 54.879573,-1.519573

In the mid 19th century, a mill operated in Fatfield. The 1857 map below confirms that this was a charcoal mill but this may have had other uses prior to this date. It was located to the west of Worm Hill alongside the stream known locally as "Biddick Burn" or "Biddick Back Burn." This burn flows through the Fatfield area and empties into the river Wear close to the mill.

Above: 1857 map showing the location of "Fatfield Mill"

Above: the same area today for comparison purposes

Fatfield Mill and Charcoal Production

So what is a charcoal mill? When we consider the likes of a corn mill, the milling is the process which grinds the corn to produce flour as the end product but what happens with charcoal? As stated further below, a foundry, for metalworking used charocal as a substance-of-choice so it was not necessary to treat (or "mill") finished charocal prior to use. It is more likely that the mill was part of the charcoal making process itself.

The charcoal making process has several important steps. In basic terms, the milling part of the charcoal-producing process involved taking pieces of wood, sawdust and other such materials and crushing them into small pieces. Whether this was the full extent of the Fatfield Mill's involvement in the process is unlikely.

The next stage in the charcoal making process is that the crushed material then needs to be dried out and compressed (into briquettes) before the carbonisation process begins. Wood consists of three main components: cellulose, lignin and water. The cellulose and lignin (and other minor materials) are tightly bound together and make up the material we call wood. Air dry or "seasoned" wood still contains 12-18% of adsorbed water. The water in the wood has all to be driven off as vapour before carbonization (ie charcoal manufacturing) can take place. To evaporate water requires a lot of energy so using the sun to pre-dry the wood as much as possible before carbonization greatly improves efficiency. The water remaining in the wood to be carbonised, must be evaporated in the kiln or pit and this energy must be provided by burning some of the wood itself which otherwise would be converted into useful charcoal.

The first step in carbonization in the kiln is drying out of the wood at 100°C or below to zero moisture content. The temperature of the oven dry wood is then raised to about 280°C. The energy for these steps comes from partial combustion of some of the wood charged to the kiln or pit and it is an energy absorbing or endothermic reaction. When the wood is dry and heated to around 280°C, it begins to spontaneously break down to produce charcoal plus water vapour, methanol, acetic acid and more complex chemicals, chiefly in the form of tars and non-condensible gas consisting mainly of hydrogen, carbon monoxide and carbon dioxide. Air is admitted to the carbonising kiln or pit to allow some wood to be burned and the nitrogen from this air will also be present in the gas. The oxygen of the air is used up in burning part of the wood charged.

On a human level, the smoke and tars produced by carbonization has a high content of carbon monoxide which is poisonous when breathed. Although not directly poisonous, they may have long-term damaging effects on the respiratory system. Housing areas should, where possible, be located so that prevailing winds carry smoke from charcoal operations away from them and batteries of kilns should not be located in close proximity to housing areas. Note the close proximity of housing to the mill and foundry!

Tars and pyroligneous liquors can also seriously contaminate streams and affect drinking water supplies for humans and animals. Fish may also be adversely affected. Fortunately kilns and pits do not normally produce liquid effluent - the by-products are mostly dispersed into the air as vapours.

One more point worthy of note is that charcoal production was often a seasonal activity. Prolonged wet wether or a harsh winter may close down operations or the labour force may traditionally be employed at certain times in harvesting or planting operations in agriculture.

The Foundry

By far the most important use for charcoal was as a metallurgical fuel. Charcoal was the traditional fuel of a blacksmith's forge and for other applications where intense heat is required. Charcoal burns at intense temperatures, up to 2700°C. By comparison the melting point of iron is approximately 1200 to 1550°C. Due to its porosity, it is sensitive to the flow of air and the heat generated can be moderated by controlling the air flow to the fire. For this reason charcoal is an ideal fuel for a forge. It is still widely used by blacksmiths today. Charcoal is also an excellent reducing fuel for the production of iron and has been used that way since Roman times. In the 16th century England had to pass laws to prevent the country from becoming completely denuded of trees due to production of iron. In the latter part of the 19th century charcoal was largely replaced by coke - baked coal - in steel making due to cost. Charcoal is a far superior fuel to coke, however, because it burns hotter and contains no sulphur. Similar to other towns and villages at that time, there were no shortage of blacksmiths and other iron/coal workers in Fatfield as the various census returns confirm. It is therefore important to note on the above map the close proximity of "Biddick Foundry" to the charcoal mill. Charcoal made in the mill would no doubt have been used at the foundry for metallurgical purposes.

Foundry work, such as would have taken place at the neighbouring Biddick Foundry, is the process of making a metal casting of an object by pouring molten metal into a mould. The mould is made using a pattern of the article required.

There are two types of foundries:

• ferrous foundries, which produce iron and steel castings
• non-ferrous foundries, which produce castings of copper-based alloys (brass, bronze), aluminium-based alloys (lead, zinc, nickel, magnesium) and other alloys

Foundry work involves numerous processes, including:

• pattern making
• core making, stoving, blowing and shooting
• mould making
• refining/alloying
• furnace and ladle maintenance
• metal pouring
• casting knockout
• abrasive blasting
• sand reclamation

Just taking the 1851 census as an example, and restricting our search to "Long Row", which was the row of houses to the west of the mill and foundry, several people's occupations bear witness to the importance of the miill and foundry at this time:

William Armstrong, aged 24, iron founder

William Hutchinson, aged 17, iron founder's apprentice

James Wilson, aged 15, iron foundry labourer

Alexander Law, aged 34, coke maker

John Ketter, aged 29, coke maker

Robert Embleton, aged 13, apprentice at iron works

Daniel Forbes, aged 37, coke maker

Johnson Morris, aged 35, iron founder

Note: A check of the 1841 census for Fatfield shows there was a miller present in Long Row: Mr John Russell, aged 30.

By the time of the 1896 map (below), the Fatfield Mill building was still standing but the foundry had been demolished and replaced with houses.

Above: Fatfield Mill and Foundry, 1896

Above: the same area in 1939, the mill has been demolished

Above: Biddick Burn. The mill once stood on the left bank of the burn

Above: the remains of the mill can still be seen today

Above: the tunnel through which the Biddick Burn flows under the road and into the river Wear. Taken from the banks of the Wear looking up-stream in the direction of Fatfield / the old mill