A basic early charcoal iron furnace

Although they often looked quite simple, a furnace could grow to be quite a complex and sophisticated structure. The need to arrange raw materials and other functions around the furnace, and the need to provide a weatherproof covering resulted in a rather distinctive building. The only really solid structure was the furnace itself. The other buildings rarely survived to the present day.

The illustration above shows a typical early charcoal furnace in the early 1700s. The furnace is the squat, square building in the centre. It is not very high because there was a limit to the height a charcoal furnace could be built. If the furnace was too high, the charcoal would be crushed under the weight of the iron ore pushed in on top of it, and the furnace would not work. Although not too apparent from the drawing, the furnace is on two levels, so that the furnace can be easily filled witouore and charcoal from the top. This explains why hilly areas such as Welsh valleys were ideal for furnace building. The uphill area on the left side of the picture would have been full of piles of charcoal and iron ore ready to be put into the top of the furnace when in blast.

The building on the lower level on the right hand side is the casting house. The casting house needed a good roof to keep the rain and bad weather away from the molten iron. Nasty explosions could occur if the iron should come into contact with water whilst coming out of the furnace. The large open arches of the casting house indicated the need to keep the area well ventilated.

Although not in this drawing the other side of the furnace will have a waterwheel to power bellows to provide the blast of air that made the furnace hot. Again a steep hillside was a bonus because it enabled a good gradient for water to run down and power the wheel. Another reason why Wales was such a good location for this industry. The sketch below explains the basic layout in more detail.

The large pile of 'sticks' in the foreground of the drawing above are the 'pigs' of cast iron which have been stockpiled for further processing for transport elsewhere. A furnace such as this may only have worked for a couple of weeks a year as it often took a long time to gather the necessary charcoal and iron ore in sufficient quantities.

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SHW's Book of the Month:

Salt by Mark Kurlansky

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This is not a local history book and Mark Kurlansky is a journalist not a local historian. Nevertheless he has produced a fascinating history of one of the world's basic commodities. I first came across Kurlansky with his book about the history of Cod. I think anyone who wants to know about the history of the Bristol Channel has to be familiar with the fish and how it encouraged Bristol fishermen to discover the Grand Banks. Salt is another offbeat yet fundamental bit of our history. We've had a popular web page on salt for ages and Swansea had a Salthouse Point at the mouth of the River Tawe for centuries. Kurlansky takes you on a journey across space and time to discover the importance of salt for mankind. From Jericho to Gandhi, salt has had an important part to play. This is a lovely book that enhances the quality of history for it adds depth and value to something we use every day. (Nigel Robins)

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