Intermittent Down Draught Kiln and Chimney, Vaal Potteries
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In the early 19th century, various technological modifications were developed to try and improve the product quality and energy efficiency of pottery kilns. In the process, first up draught and then down draught kilns were developed.
A down draught kiln is an intermittent kiln in which the kiln charge is fired in batches. It consists of a firing chamber or kiln connected to a chimney through an underground flue duct. A series of fire boxes are provided on the external edge of the firing chamber where the fuel is burnt.
In such a kiln the hot gas from the burning fuel in the fire boxes is directed to the arched roof of the kiln and then drawn downwards by the chimney draught through the kiln charge.
One of the advantages of a down draught kiln is that the fuel and fuel residue do not come into contact with the kiln charge and therefore no pollutants are deposited on the surface of the products. There is also uniform heat distribution in a down draught kiln and the percentage of good quality products is therefore generally high.
A redundant down draught kiln and chimney was dismantled and relocated to a site some 40 metres from the main entrance to the Vaal Potteries Administration Building.
The kiln structure is built with fired bricks and the inner surface of the kiln is lined with refractory bricks.
Transcript of commemorative plaque mounted within the kiln:
William Martinson, February 2020.