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Saggars and Placers: Mastering the Art of Bottle Kiln Firing

Firing a bottle kiln or oven. What was the role of 2000 saggars or the placers that filled the brick structure? Mastering this art was critical to producing the fired pottery or ceramics. Each pot bank made its own saggars from fire clay. In the saggar maker's workshop, clay would be rolled around a wooded form by the saggar maker, while a lad would knock the bottom using a mawl and an iron mould. A saggar could be expected to last for 30-40 firings after which it had to be replaced. During biscuit firing, tableware cups and bowls were put on a fine layer of calcined flint dust on the bottom of the saggar, while flatware was supported like a sandwich between layers of flint. They had to be stacked carefully to prevent distortion during firing. Then the saggar was topped and sealed to prevent any fumes or kiln debris entering the saggar and discolouring the wares. During the second firing, the glost firing, the glazed ware was held by pins, saddles, spurs and thimbles, as any contact point would leave a blemish on the glaze. Sorting the thimbles for reuse was one of the lowest jobs in the potbank. Placing and drawing the kiln was the job of placers. Placers would take the unfired greenware that was drying in the greenhouse (or the glost placing shop) and stack it in the saggar. They would seal the saggar, then carry it into the bottle oven on their heads. Each loaded saggar weighed around 56 lb (25 kg). They were stacked in bungs in such a way that the most delicate wares were protected. A bung of saggars would be 12 or 13 high, on the top of the bung would be unfired newly moulded green saggars. In the centre of the bottle oven is the well-hole, over it, saggars with no bottoms would be placed in the pipe-bung: this formed a chimney to draw the fires. When the kiln was full, the clammins were bricked up leaving one brick short to form a spyhole so the firemen could watch the Buller's rings to judge the temperature of the firing. The potbank employed a cod placer to supervise the work, but placers who were paid by the job used to wait outside the potbanks for work. Drawing would be done 48 hours after firing finished but in hard times placers were sent into a kiln that was still glowing red after 24. The men wore five layers of clothing and wet cloths over their heads. Life expectancy for a placer was low. A bottle oven would be fired once a week. The fires were set in each of the firemouths by the firemen. Once alight the kiln would be heated slowly as the moisture was burned out of the clay, this was known as "smoking". Then the kiln would be taken to full temperature, and kept there for three hours then allowed to cool. A biscuit firing took three days and a glost firing took two days. After 48 hours the kiln had cooled sufficiently to be drawn by the placers, and the wares checked. The placers' earnings were dependent on the success of the firing. Each firing would use 14 tons of coal. It was very energy inefficient, and popular sources say that between 50% and 95% of the heat was lost up the chimney. Coal burning is a very dirty process; the smoke from a bottle kiln would eddy around the kiln top, and curl down to ground level either into the yard of the pot bank or into the streets and houses around. There are 47 standing bottle ovens in Stoke-on-Trent, all are now listed buildings. The largest group is to be found in Longton within its conservation area which protects a number of 19th century pottery works. Like Pottery or Ceramics? Discover more of the legacy of the British Potteries and its world heritage on the ‪@PotteriesAuthor‬ Channel. All the links to find out more about me at https://linktr.ee/authoronthepotteries #saggars #placers #bottle #kiln #oven #stokeontrent #longton #firing #lastfiring #bottomknocker #clay #marl #bung #potbank #fireclay #greenware #unfired