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Charcoal BurningThe Forest of Dean was an area of national importance in iron production for many hundreds of years. There are two main components in iron production, iron ore and a reducing agent. The Forest of Dean had an abundance of iron ore and wood which made it a natural centre for production of iron. However wood in its native form simply does not burn at a high enough temperature to be a suitable reducing agent in the iron production. Charcoal burns at the necessary temperature (2012 degrees Fahrenheit / 1100 degrees Centigrade), and was therefore used locally in the smelting of iron from as early as 450BC right up until coke became available in the 18th century.
There is plenty of historical evidence in the woods of the Dean of the more traditional method of producing charcoal. Because something like 10 tons of wood are required to produce 2.5 tons of charcoal, there was little point in hauling the raw material to a point of production, instead the charcoal was produced within the woods, and then taken to the forges. The evidence of that production comes in the form of areas, some 8 yards in circumference, on which the wood stack was built before firing.
Producing charcoal in this way is a very skilled process, the last exponent in the Dean being Edward Roberts in the 1950's, who used the same techniques that had been used for centuries before. To produce charcoal, Edward would find a site which had a clay soil content, then measure the area with his boots to a size of between twelve and sixteen feet in diameter. He would then dig out the area to a depth of 18 inches. He would then carefully build the stack, starting with a tripod four feet in height in the centre, which formed a chimney. Lengths of cord wood were then added in a system of tiers designed to give the stack a semi circular profile. Edward would then cover the construction with turf or soil, taking care to leave small vent holes every three feet round the circumference of the pit. He would fire the pit by dropping an amount of charcoal embers down the fire hole in the centre. An iron lid, some 3 feet in diameter would then be placed across the fire hole at the top of the stack. The stack would start to combust with smoke pouring out of the vent holes.
It was very important that very little or no air was allowed into the stack during the combustion process, so the charcoal burner had to be at hand for the three or four days of the burn to repair any cracks that appeared in the turf or soil walls of the stack. The change in colour of the smoke being emitted from white to blue gave Edward the signal that the burn was complete and he would then block the vent holes and allow the stack to cool for another two or three days. Opening the stack to recover the charcoal was always a tricky moment, as there was always the danger that the charcoal might re-ignite. Edward always kept a keg of water nearby to make sure he could put out any unwanted fires! It would then take him another two days or so to sort and bag the charcoal. In the days of his father, who preceded him as a charcoal burner, much of the charcoal was taken away by strings of donkeys.
It was obviously more efficient for Edward to deal with as many stacks as he could manage, so subject to the availability of wood within the locality, he would start a sequence of stacks burning at perhaps three day intervals. Obviously the stacks required attention day and night and had to be examined at two hourly intervals, so often Edward would build a log hut in the wood adjacent to his work place. He would draw on the same skills he used to build his stacks to construct his hut, using three stout clothes props in a wigwam form as the basis, then carefully arranging logs in a cone shape around them.
The tradition of charcoal burning has not entirely been lost from the Forest, as the Dean Heritage Centre regularly carries out charcoal burning in just the same way as Edward Roberts did.
Photographs of charcoal burning from the Dean Heritage Centre. You may view this yourself in the summer months, but it is best to telephone the centre on 01594-822170 first to find out the dates when charcoal burning is taking place.
During the 1800's production of charcoal and other products started on an industrial basis at chemical or wood distillation factories. A number of these existed around the Forest area, including plants at Lydbrook, Oakwood and Cannop. Some idea of the scales of production can be obtained by studying the wood distillation works built by the Government at Speech House Road in 1913-1914. An input of some 12000 tons of wood annually could produce 384 tons of acetate of lime, 270 tons of wood tar, 1380 tons of charcoal and 90 tons of wood spirit. The works were centrally located in the Forest, in a place served by four roads and a railway siding. The process involved charging the retort (56 feet in length and 7.5 feet in diameter) with suitable cordwood. The retort was then sealed by closing the door, and hot flue gases from a coal furnace were then passed through it. Two pipes in the roof of the retort allowed the vapour and gas to be led away for processing. The retort was heated for 24 hours then the charcoal was removed into another chamber where it was cooled for a further 24 hours. The process was kept continuous by then immediately charging the retort with another load of cordwood. Production continued on the same site until 1971.
Article written by Keith Walker
Forest of Dean History Society
Photographs courtesy of the Dean Heritage Centre
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