The history of china clay in Cornwall and Devon
China clay is decomposed granite where the feldspar had changed into a fine, white powder known as kaolin. Certain parts of the granite uplands, both in Cornwall and Devon process this substance. Today china clay is only mined in the Hensbarrow Moors north west of St. Austell and at Lee Moor- on Western Dartmoor, though in the past kaolin has been extracted on Bodmin Moor, West Penwith and Tregonning Hill, where it was first ‘discovered’ by William Cooksworthy in the 1740s.
In China kaolin had been used since AD700 to create a particularly fine type of pottery- porcelain but the Europeans were unable to discover its secrets. The Cornish kaolin was known to be exceptionally heat resistant and used in tin smelting, but it was Cooksworthy who discovered its potential for pottery manufacture.
The first clay pits were small, compared with today’s workings and tended to be very shallow to avoid the cost of pumping. The processing of the clay was particularly inefficient as clay was dried in the open, often taking several months. Artificial drying commenced in the 1840s, resulting in a great increase in production. Steam engines also began to appear at this time to pump the clay slurry, allowing pits to become much deeper. By 1914 there were 159 active clay works though many were small pits, controlled by independent companies but following the First World War, consolidation was needed to expand existing pits and modernise its production methods. In 1919 three of the largest companies amalgamated to form English China Clays Ltd (ECC). Many pits were closed in the Second World War when demand drastically fell and rationalisation was needed. Several of these pits are abandoned to this day, giving a good insight into historical methods of extraction and processing.
In 1999 ECC was acquired by the French company Imetal who subsequently changed their name to Imerys who have since closed several major pits and processing facilities as they move there operations abroad. In 2012 they bought the last independent clay company: Goonvean and Rostowrack China Clay Co, giving Imerys complete monopoly of the industry.
The Moors around St. Austell are now dominated by the huge mountains created from the waste rock and sand extracted from vast pits. Unlike the tin and copper mines, the china clay industry has received very little attention, mainly because this is still a major industry with many important sites left to decay. Much of the archaeology has been destroyed over time as pits expanded taking engine houses, dries, and houses with them. It is sad to see what has been lost since the Cornwall Archaeology Unit carried out an extensive survey in the early 90s. Major losses since then include the 1930s power station at Drinnick, Charlestown foundry, the house of last pumping engine to work in Cornwall at Greensplatt- it stopped working in 1959 and the engine was removed in the 70s and is now at the Poldark museum, the village of Greensplatt, and Goonvean engine house which still contained its engine until demolition when it was removed to Hayle in 2008. What is partially sad about its loss, together with the earlier engine house and splendid pan kilns is that when Imerys took over the company only a few years later, they abandoned the pit, making the obliteration a site of huge importance completely pointless.
Over the past two years I have visited and recorded a great number of the surviving remains and have decided to use my photos to show the process of clay extraction and what survives. I still need to explore the other areas of clay extraction in Cornwall and Devon, but this report virtually covers the whole process.
English Clays Lovering Pochin logo on the wall of a concrete block works. ECC later merged with two other companies becoming ECLP before ECC acquired the rest of the shares in the 1950s
Pre-war china clay extraction process:
There is a great deal of remains from the traditional process of china clay extraction, though this is only a fraction of what there once was as pits enlarge, removing all traces of earlier workings.
Diagrams showing the typical arrangement of the pre-war refining and drying process
A typical old clay pit seen from a tip. This was one of many which closed in 1942 and never reopened, showing the steep sides and a small tip as seen from the largest sky tip. Note the waterline halfway up the cliff face, a pit recently broke into the older workings though this now seems to have been abandoned in the early stages
Rather than going down, this earlier pit was cut into the side of a valley. I took this photo looking back towards the entrance of what now appears to be a natural landscape
One of the finest remaining sky tips, 60 years ago the whole area surrounding St. Austell was packed with dozens of white pyramids, but now the few which survive are often hidden in forests of rhododendrons
Looking at the sky tip where I took the first photo from, seen from the other large tip
A view of a more recent sky tip, in the foreground is part of the mechanism for raising the skips up the incline
The remains of a horizontal steam engine at the base of a tip
The Cornish boiler also survives, though it now rests downhill from its original location
The remains of a very similar winding engine survive in better condition, the boiler has been removed to Lelant engine house
A rather complete winding drum sits on a concrete base the rest of the engine has been cut up for scrap but why they left the drum I don’t know. If only there were more places like this...
This is how it would have looked: the winder at the King Edward Museum
A smaller winding drum seen from a path at the Wheal Martyn Museum
Another Cornish boiler, note the sand in between the inner and outer sections, presumably to insulate it
A single beam engine has thankfully been preserved near St. Dennis and is now the only complete steam engine surviving in its house of the dozens which were built in the area. I believe there are four other surviving beam engines from clay works which have been removed from their houses. This was a permission visit and the engine house is now in the middle of a modern clay plant.
External view, showing the tall engine house with the beam on the left, the winder house in the foreground and the boiler house to the right of the engine house with the chimney hidden behind the trees.
The top floor of the engine house, showing the beam built by Sandys Vivian & Co. Hayle in 1852. The engine first worked at a tin mine in St. Agnes before being taken here in 1912. As the tin and copper mines declined many of their steam engines found their way to various clay works. This was one of the last engines working in the area, in use until 1953
The complete Lancashire boiler built by H. & T. Danks Ltd, Netherton, near Dudley
The interior of the winder house
This ruined beam engine house is fenced but the shaft is open and unfenced!
This 1915 engine house still retains its original roof although the brick chimney and surrounding buildings have long gone. The engine was replaced by electric pumps in 1944 and put in store at the Science Museum
Another more recent engine house with Cornwall's best-known sky tip behind. Between the two is vast, abandoned pit
A shaft containing the rising main (iron pipe) and pump rod still in-situ, surrounded by a dodgy fence in dense undergrowth
Another rising main, marking the location of a very blocked shaft
Waterwheels
Water wheels were once common on many clay works as a cheaper alternative to steam pumping engines. Waterwheels were especially common on the Bodmin Moor pits where there are only two recorded engine houses.
The preserved 35ft waterwheel at Wheal Martyn was used to pump water from a pit some distance away by means of reciprocating iron rods known as flat rods, seen at the centre of the wheel. To the right of the wheel is a balance bob, used to reduce the reduce the work of the wheel. At the nearest end is the counterweight, filled with stones. There is also a preserved 15ft wheel, also used for pumping
The wheel pit and support for the launder for a 50ft wheel used to pump from a pit one and a quarter miles via a system of flat rods over Bodmin Moor. This wasn’t particularly successful, so a generator house was later built to replace the rods. The wheel was removed in the 1960s to a mining museum in Wales, leaving the very deep pit.
Part of a balance bob near the remains of a waterwheel. When I first visited I found the broken remains of the wheel buried under rocks but now a new track has buried it completely with the balance bob just below the dumped material
Preserved mica drags at Wheal Martyn, to the right are a series of settling pits
Mica drags in mature woodland in Bodmin Moor from a works which was abandoned over 100 years ago
more to come...
China clay is decomposed granite where the feldspar had changed into a fine, white powder known as kaolin. Certain parts of the granite uplands, both in Cornwall and Devon process this substance. Today china clay is only mined in the Hensbarrow Moors north west of St. Austell and at Lee Moor- on Western Dartmoor, though in the past kaolin has been extracted on Bodmin Moor, West Penwith and Tregonning Hill, where it was first ‘discovered’ by William Cooksworthy in the 1740s.
In China kaolin had been used since AD700 to create a particularly fine type of pottery- porcelain but the Europeans were unable to discover its secrets. The Cornish kaolin was known to be exceptionally heat resistant and used in tin smelting, but it was Cooksworthy who discovered its potential for pottery manufacture.
The first clay pits were small, compared with today’s workings and tended to be very shallow to avoid the cost of pumping. The processing of the clay was particularly inefficient as clay was dried in the open, often taking several months. Artificial drying commenced in the 1840s, resulting in a great increase in production. Steam engines also began to appear at this time to pump the clay slurry, allowing pits to become much deeper. By 1914 there were 159 active clay works though many were small pits, controlled by independent companies but following the First World War, consolidation was needed to expand existing pits and modernise its production methods. In 1919 three of the largest companies amalgamated to form English China Clays Ltd (ECC). Many pits were closed in the Second World War when demand drastically fell and rationalisation was needed. Several of these pits are abandoned to this day, giving a good insight into historical methods of extraction and processing.
In 1999 ECC was acquired by the French company Imetal who subsequently changed their name to Imerys who have since closed several major pits and processing facilities as they move there operations abroad. In 2012 they bought the last independent clay company: Goonvean and Rostowrack China Clay Co, giving Imerys complete monopoly of the industry.
The Moors around St. Austell are now dominated by the huge mountains created from the waste rock and sand extracted from vast pits. Unlike the tin and copper mines, the china clay industry has received very little attention, mainly because this is still a major industry with many important sites left to decay. Much of the archaeology has been destroyed over time as pits expanded taking engine houses, dries, and houses with them. It is sad to see what has been lost since the Cornwall Archaeology Unit carried out an extensive survey in the early 90s. Major losses since then include the 1930s power station at Drinnick, Charlestown foundry, the house of last pumping engine to work in Cornwall at Greensplatt- it stopped working in 1959 and the engine was removed in the 70s and is now at the Poldark museum, the village of Greensplatt, and Goonvean engine house which still contained its engine until demolition when it was removed to Hayle in 2008. What is partially sad about its loss, together with the earlier engine house and splendid pan kilns is that when Imerys took over the company only a few years later, they abandoned the pit, making the obliteration a site of huge importance completely pointless.
Over the past two years I have visited and recorded a great number of the surviving remains and have decided to use my photos to show the process of clay extraction and what survives. I still need to explore the other areas of clay extraction in Cornwall and Devon, but this report virtually covers the whole process.
English Clays Lovering Pochin logo on the wall of a concrete block works. ECC later merged with two other companies becoming ECLP before ECC acquired the rest of the shares in the 1950s
Pre-war china clay extraction process:
There is a great deal of remains from the traditional process of china clay extraction, though this is only a fraction of what there once was as pits enlarge, removing all traces of earlier workings.
Diagrams showing the typical arrangement of the pre-war refining and drying process
- First the clay pit itself where clay was extracted from the rocks and dissolved in water
A typical old clay pit seen from a tip. This was one of many which closed in 1942 and never reopened, showing the steep sides and a small tip as seen from the largest sky tip. Note the waterline halfway up the cliff face, a pit recently broke into the older workings though this now seems to have been abandoned in the early stages
Rather than going down, this earlier pit was cut into the side of a valley. I took this photo looking back towards the entrance of what now appears to be a natural landscape
- Next the waste material is transported to the tips
One of the finest remaining sky tips, 60 years ago the whole area surrounding St. Austell was packed with dozens of white pyramids, but now the few which survive are often hidden in forests of rhododendrons
Looking at the sky tip where I took the first photo from, seen from the other large tip
A view of a more recent sky tip, in the foreground is part of the mechanism for raising the skips up the incline
- Steam engines were often used to raise the skips and several engine houses survive, some with the remains of their steam engines and equipment
The remains of a horizontal steam engine at the base of a tip
The Cornish boiler also survives, though it now rests downhill from its original location
The remains of a very similar winding engine survive in better condition, the boiler has been removed to Lelant engine house
A rather complete winding drum sits on a concrete base the rest of the engine has been cut up for scrap but why they left the drum I don’t know. If only there were more places like this...
This is how it would have looked: the winder at the King Edward Museum
A smaller winding drum seen from a path at the Wheal Martyn Museum
Another Cornish boiler, note the sand in between the inner and outer sections, presumably to insulate it
- The clay slurry was pumped to the processing area via a steam engine or water wheel from a shaft connected to the pit
A single beam engine has thankfully been preserved near St. Dennis and is now the only complete steam engine surviving in its house of the dozens which were built in the area. I believe there are four other surviving beam engines from clay works which have been removed from their houses. This was a permission visit and the engine house is now in the middle of a modern clay plant.
External view, showing the tall engine house with the beam on the left, the winder house in the foreground and the boiler house to the right of the engine house with the chimney hidden behind the trees.
The top floor of the engine house, showing the beam built by Sandys Vivian & Co. Hayle in 1852. The engine first worked at a tin mine in St. Agnes before being taken here in 1912. As the tin and copper mines declined many of their steam engines found their way to various clay works. This was one of the last engines working in the area, in use until 1953
The complete Lancashire boiler built by H. & T. Danks Ltd, Netherton, near Dudley
The interior of the winder house
This ruined beam engine house is fenced but the shaft is open and unfenced!
This 1915 engine house still retains its original roof although the brick chimney and surrounding buildings have long gone. The engine was replaced by electric pumps in 1944 and put in store at the Science Museum
Another more recent engine house with Cornwall's best-known sky tip behind. Between the two is vast, abandoned pit
A shaft containing the rising main (iron pipe) and pump rod still in-situ, surrounded by a dodgy fence in dense undergrowth
Another rising main, marking the location of a very blocked shaft
Waterwheels
Water wheels were once common on many clay works as a cheaper alternative to steam pumping engines. Waterwheels were especially common on the Bodmin Moor pits where there are only two recorded engine houses.
The preserved 35ft waterwheel at Wheal Martyn was used to pump water from a pit some distance away by means of reciprocating iron rods known as flat rods, seen at the centre of the wheel. To the right of the wheel is a balance bob, used to reduce the reduce the work of the wheel. At the nearest end is the counterweight, filled with stones. There is also a preserved 15ft wheel, also used for pumping
The wheel pit and support for the launder for a 50ft wheel used to pump from a pit one and a quarter miles via a system of flat rods over Bodmin Moor. This wasn’t particularly successful, so a generator house was later built to replace the rods. The wheel was removed in the 1960s to a mining museum in Wales, leaving the very deep pit.
Part of a balance bob near the remains of a waterwheel. When I first visited I found the broken remains of the wheel buried under rocks but now a new track has buried it completely with the balance bob just below the dumped material
- The clay slurry was pumped from the pit to be possessed, first by drags used to remove the mica using long, gently sloping channels to catch the solid waste at the bottom while the clay slowed down.
Preserved mica drags at Wheal Martyn, to the right are a series of settling pits
Mica drags in mature woodland in Bodmin Moor from a works which was abandoned over 100 years ago
more to come...
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