Staffordshire has many hidden gems. At Etruria, situated at a beautiful spot at the junction of two canals in the heart of Stoke-on-Trent is Jesse Shirley’s Bone and Flint Mill, the only Victorian working steam driven potters’ mill in the world and one of few original working industrial heritage sites in Staffordshire. Bernard Lovatt takes a look at the history of the mill industry.
WITH Grade II listed buildings and milling equipment dating from 1857, powered by a large beam engine built in the 1820s, Jesse Shirley’s Bone and Flint Mill forms an important part of Staffordshire’s industrial heritage — and yet is little known.
The Mill, which is a scheduled ancient monument together with other buildings including a visitor’s centre, form the Etruria Industrial Museum which is open for steaming weekends when the plant may be seen running as it did in 1857.
The need for ground flint and bone arose in the second half of the 18th century when the potters of Europe were experimenting to reproduce the highly prized fine porcelain imported from China and developed from the Tang dynasty 618-906AD through to the Ming dynasty 1368-1644AD.
The expanding middle class was demanding the same standard of pottery used by the upper class but at an affordable price. By 1708, in Saxony, a hard white translucent porcelain was being produced using kaolin clay, calcined alabaster and quartz.
In 1748 Thomas Frye at the Bow Porcelain factory in East London, used bone with other materials to produce Bone China. The guides at the Etruria Industrial Museum often see the horror on visitors’ faces when they realise that the fine china they drink their tea from is made from 50 per cent animal bone.
Between 1789 and 1793 Josiah Spode developed the process and was able to make a fine translucent strong material which was a commercial success — others followed. The basic formulation was 25 per cent china clay (kaolin), 25 per cent flint and 50 per cent bone. The flint and bone, after it had been calcined was ground to a fine powder. This was originally done using adaptions of corn mills but the dry process was a major health hazard with workers dying of silicosis within six years. In 1726 Thomas Benson had patented a process for wet grinding of flint and this was adopted by the potters. As demand increased, many flint and bone mills appeared, initially powered by water — but by 1800 increasingly by steam.
Originally bone, usually cattle bone, would have been sourced locally and latterly bone came from overseas. Flint was supplied from outcrops in chalk strata on the Isle of Wight and the south coast as well as the coast of Lincolnshire and South Yorkshire. More recently flints have been obtained from chalk pits in Southern England and, when demand was high, from beaches in Belgium and Northern France. The raw materials were brought to the Mill via the canal network. Some of the product went to the potters via horse and cart, but most went along the canal.
The calcining process was done in a kiln with the bone or flint heated to around 1000OC. This drove off the water and changed the nature and colour of the material so grinding to a fine white powder was possible. Filling the kiln was a very skilled job requiring layering of fuel with either the bone or flint. Coal was used to calcine flint with one hundredweight of coal used per ton of flint. Bone, being an organic material which burns more easily, used wood as the fuel to prevent contamination by iron pyrites in the coal.
The time taken to calcine flint was between eight to 16 hours. but bone would be quicker. With cooling the process took over 24 hours. Production of ground flint ceased at the Mill in the 1930s as more Cornish stone was introduced to the process. A ton of bone would make about 2,500 bone china Staffordshire has many hidden gems. At Etruria, situated at a beautiful spot at the junction of two canals in the heart of Stoke-on-Trent is Jesse Shirley’s Bone and Flint Mill, the only Victorian working steam driven potters’ mill in the world and one of few original working industrial heritage sites in Staffordshire.
Jesse Shirley, born in 1819, was employed by his step-father John Bourne in 1834 at his firm of Bourne and Hudson Bone Works originally as a writing clerk. When John Bourne died in 1852 he left the business to brothers Joseph and Jesse Shirley. It was the latter who had the present Mill constructed in 1856/1857 by George Kirk of Etruria. The road access to the site was poor so the location was no doubt chosen because of the proximity to the canal and the existence of a branch and wharf directly from the Trent and Mersey Canal. Around the site there would be 12 to 14 men employed and whilst the work would be arduous, dusty and very smelly, it is apparent that employees might spend most of their working lives there. It must have been regarded as a good place to work. At its peak the Mill was producing 80 to 100 tons of products per week and was also used for milling fertilizer.
The Mill is powered by “Princess” a double acting condensing rotative beam engine to the design of James Watt. With a 34inch cylinder, 18ft beam and 20ft flywheel, each weighing around 10 tons, she occupies her own engine house with attached boiler house. ‘Princess’ was installed when the mill was built in 1857 but was second hand. Her previous history is unknown but she was almost certainly built by Bateman and Sherratt of Salford in the 1820s. As the Boulton and Watt patents ran out around 1800, many engineering companies started to produce steam engines. In a letter to Josiah Wedgwood II, James Watt refers to them as the Manchester pirates. Bateman & Sherratt set up the Salford Iron Works, and became one of the largest manufacturers of cast iron products and stationary steam engines, outselling even Boulton & Watt. They manufactured the first marine steam engine.
Bateman also had banking interests and became a very rich man. He retired to live with his son, John, a notable horticulturist at Knypersley Hall in North Staffordshire. John and his son James, who became a Fellow of the Linnean and Royal Society and Vice-President of the Royal Horticultural Society bought The Grange at Biddulph in North Staffordshire and created another of Staffordshire’s gems, the extraordinary garden at Biddulph Grange.
Steam for the engine is generated in a hand fired ‘Cornish’ boiler containing 2,500 gallons of water. It was built by William Evans Boiler Works at nearby Cliffe Vale in 1903. Although not original, the boiler is an important piece of industrial heritage in its own right and is thought to be one of the oldest boilers in the world still working. Due to the thermal capacity and the need to heat the boiler, flues, brickwork and water slowly the fire is lit on Monday for steaming the following Saturday and is tended for five hours every day by two stokers.
Power from the engine is transmitted via the flywheel axle and vertical shafts to grinding pans on the upper floor of the Mill.
Paddles push large chert stones, some weighing up to 1 ton round the pans which grind the bone or flint to slurry. This is run off to the lower floor and allowed to settle in arks before removal and delivery to the customer.
The Mill operated from 1857 to 1972 when for economic reasons it was replaced by modern machinery. The workforce walked out and locked the door on the Friday and started work in the new factory next door on the Monday. This left partly ground material in the pans which solidified and caused problems in removing it when restoration commenced in 1978 but the Mill was almost as it was in 1857 with even the special size and shaped spanners for the engine, wooden patterns for the gear wheels and metal parts for the pans and items such as wheelbarrows left intact.
Much credit for this must go to the Shirley family who were still running the business and continued until production ceased in 2011 for keeping the old Mill intact.
The Mill is maintained and operated by volunteers in partnership with Stoke-on- Trent City Council. It is hoped to transfer it to a charitable trust to secure its future and retain it for education, tourism, steam and ceramics enthusiasts and, most important of all, to preserve it to inspire future generations.
Guided tours are available conducted by knowledgeable volunteers. More information is available at www.friendsofetruriamuseum.org.uk where a video of the mill in operation can be viewed — there is no substitute for seeing it live.
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