Today we visit the Cornish Mines & Engines nearby Redruth and the Cina Clay Museum nearby St. Austell

Cornish Mines & Engines

At the very centre of the Cornish Mining World Heritage site, these two grat beam engines sit preserved in their towering engine houses - a reminder of Cornwall's days as a world-famous centre of industry, engineering and innovation. Both engines are originally powered by high-pressure steam, introduced by local hero Richard Trevithick.One can still be seen in action, rotated by electricity, with the great beam rising and falling. The Discovery Center gives you the whole dramatic story of Cornish mining, with an atmospheric film and static displays. Don't miss the experience of walking through the flue tunnel and the dizzying view up inside the 36m chimney stack.

Wheal Martyn - China Clay Museum

Wheal Martyn was established in 1975 by the producers of China Clay in Cornwall to preserve and record the history of the mid-Cornwall area. The site is situated alongside the St. Austell River in a valley which contained several China Clay works. The museum itself is located in two old China Clay works, Wheal Martyn and Gomm.

The Gomm works were leased by the Martin Brothers from the Mount Edgcumbe Estate in about 1878, and were worked until the 1920s. The buildings now from the main entrance to the museum, the shop and the coffee shop.
Wheal Martyn China Clay works began working much earlier, in the 1820s. They were started by Elias Martyn on the Carthew Estate became one of the major clay producers in Cornwall. In the 1840s he operated five pits and by 1869 was producing 2,000 tons of clay a year at Wheal Martyn. After Elias' death in 1872 the family kept the land at Carthew, but his son Richard Uriah Martyn closed down or leased the works to other operators.
In 1880 John Lovering took on the lease at Wheal Martyn. Lovering was an inventive clay-producer who introduced many new ideas to Wheal Martyn and it is likely that there were many changes at the works. It is essentially, therefore, his works that are visible today. Wheal Martyn pit worked until the effects of poor trade forced its closure in 1931. The dry continued to operate until 1969, working lower grade clay from pits further up the valley. Wheal Martyn Pit reopened in 1971 and continues to be worked today by ECC International Europe. The clay works opened as part of the museum in 1975 and in 1979 they were scheduled as an Ancien Monument.


The China Clay Industry

The China Clay Industry is Cornwall's largest industry. There are four companies operating pit in Cornwall and Devon, producing almost three million tonnes of clay a year.

What is China Clay used for?

Today, around 80% of the china clay produced is used in paper. (40% in paper filling and 40% in coating). Of the rest 12% ís used by the ceramics industry and the remainder in a large variety of products which require an inert filling agent; it can be found for example in many paint, rubber, plastics, cosmetics, pharmaceuticals, cork and agricultural products.

What is China Clay?

China Clayor Kaolin is formed as a result of decomposition of some of the feldspar in Granite. The feldspar changes into a fine white powder, but the other parts of the Granite, Mica and Quartz remain unchanged. This process is known as "Kaolinisation".

The China Clay Story

The Chinese have used Kaolin and Petuntse (China Stone) for centuries to make Porcelain, but the recipe remained a secret to Europeans until the beginning of the 18th Century. The first true hard paste porcelain was produced in Europe, when deposits of the raw materials were found in Saxony and then later in France.
However, in Cornwall the "secret" ingedients of Porcelain had been used for a long time. China Stone was quarried as a local building material and China Clay was used to line smelting furnaces. Their potential remained unrecognised until a Quaker Apothecary from Plymouth, William Cookworthy,first "discovered" them in about 1746, during a visit to some mining works at Tregonning Hill near Heslton. He later found better deposits at St. Stephen near St. Austell.

Cookworth experimented to produce the first hard paste Porcelain in this country and finally patented his formula in 1768. With control over the use of China Clay and China Stone for porcelain manufacture, Cookworthy opened his own Pottery at Coxside in Plympouth. Although the porcelain was in high demand, difficulties with the production process led to continuous financial problems. In 1770 the pottery moved to Bristol. Four years later Cookworthy retired and transferred his business to his partner Richard Champion. Almost immediately Champion applied for an extension to the original patent, but this was met with opposition from the potters of Staffordshire, led by Joshoa Wedgwood. They were keen to use china clay in their own wares.

After Champion's monoploy was broken, the Staffordshire compnaies leased pits of their own in Cornwall, but by 1830 they had given up control of the production to others.
They bought their supplies from agents or from the groups of adventurers who were working the clay pits.
Many of these adventureres were to found the first china clay companies. More uses were found for china clay in the paper and cotton industries, and production began to increase.
By 1858 there were 42 companies producing about 65,000 tons of clay a year.


Winning the Clay

In Cornwall, China Clay has always been extracted by using water to wash the soft kaolinised granite. The waste quartz and mica are then removed and the clay is dried.
In the earliest days of the industry, hillside sites wwre chosen so that a stream of water could be easily diverted to the clay face where
"The clay itself is dug progressively in steps, the discoloured portions being piocked out and thrown away. The selected clay is then wheeled to the washing polace or "strake", and washed with a stream of water". (Dr Fitton, 1807)

When John Lovering first took over Wheal Martyn in the early 1880s, the common practice was to run a stream of water directly over the kaolinised granite (the "stope") and break it up with picks. The stream of clay slurry flowed on down to the bottom of the pit where large amounts of quartz sand were removed. The clay slurry was then taken to the surface by pumps, or through a tunnel called an adit, to be refined.

1. Hoses and Monitors

A stream of water flowing over the clay face is not very strong, so by the end of the nineteenth century experiments had begun to use hoses to wash the clay. By the 1920s hoses were common and were operated by one man directing a jet of water onto the clay face. These hoses are now called Monitors and are operated by remote control. They can wash the clay at a pressure of 300lbs per square inch.

2. The 35ft Water-Wheel

As china clay pits grew bigger and deeper clay slurry needed to be pumped the surface. Water-wheels were used to operate the pumps, althoug many water replaced by steam engines. The 35' (10,7 m) water-wheel at Wheal Martyn was originally used to pump clay slurry from the pit. It is a pitch-back wheel and the largest working water-wheel in Cornwall.

As with many china clay pits Wheal Martyn was some distance away from the water supply needed to turn the water-wheel. This problem was solved by a system of iron rods, called "flat rods". They transmitted power from the water-wheel by means of a reciprocating action driven to and fro by a crank on ther wheel's axle. They travelled uphill over small supportuing wheels for over half a mile to the pit. They went through the pan kiln, over setting tanks and through a tunnel before turning down into the pit to connect with the pumps.
The water-wheel was made at Charlestown Foundry in the nearly 1880s. It appears on a map of 1884 and may have replaced an earlier water-wheel on the same site. The water-wheel stopped work in about 1940 and was restored to working order in 1976.

The Fire End

In this building are the coal fired furnaces which heated the pan kiln which dried the clay. (The pan kiln is number 11 on the Historic Trail). Abaut 15 tons of coal was used here every week. A ton of coal was needed to dry 10 tons of clay.
The coal stage area now houses a reconstructed BLACKSMITHS SHOP, a feature of many clay works. The pit smith would have made and repaired tools and shod the horses used in the industry.


3. The Level


This reconstracted wooden tunnel illustrates the method by which clay slurry was taken from the bottom of the clay pit to the shaft and pumps at the side. The level would have been dug through soft crumbly granite from the pumping shaft to the pit bottom. At the end of the level, a vertical shaft called the rise was made to reach up to the bottom of the pit. An upright square pipe, called a button hole lander, was used to control the flow of slurry into the shaft.

4. The 18ft Water-Wheel

When the clay slurry reached the Wheal Martyn works it was pumped around the site using a slurry pump (9). The pump was powered by this 18' (5,5m) overshot water-wheel, which was built here in about 1902.

The balance box was needed to keep the wire cable in tension, to partially compensate for the weight of the pump and keep it operating smoothly. Above the water-wheel is a wheeled guide or "pin-wheel" which connects the flat rod from the wheel's crank to the cable transmitting power to lift the slurry. The pump can be seen ahead, up the hill.


5. The Incline (Reconstruction)

Waste material from the pit would have been transported to a spoil tip on the surface by an inclined tram road. The bottom of such an incline, known as the "Dog's hole" is reconstructed here.
For every ton of china clay produced here could be as much as 7 - 10 tons of waste material. This was mostly coarse quartz sand and rock, which was seperated from the clay slurry at the bottom of the pit. The slurry ran through a sand trap where the coarser particles settled out. It was dug out by hand, loaded into wagons and trammed to the dog's hole at the base of the incline.

The waste was then transfered to another wagon, called a skip. It was then hauled up the incline out of the pit and then emptied at the top of the tip. The power came from a steam engine or sometimes a water-wheel. This process resulted in the conical "Sky Tips" which were a feature of the area.


Refining the Clay

The slurry which was pumped from the pit still contained fine grains of sand and mica as well as china clay held in suspension in the water. In such a suspension, the coarser particles will settle faster than fine particles. The Wheal Martyn Works demonstrates this principle (Stock's Law) in the treatment of clay slurry at this point.


The Crib Hut

Every clay works would have had a shelter or hut where workers could eat their "crib" at meal breaks. This crib hut was used by the workers in the refining area.


Working at the Clay Works

Most boys would start work once had left school at the age of 14, although many started much younger. Their first jobs would often be with their father or older brother, and they were known as Kettle or Tool boys. The boys were expected to make the tea for crib, look after the tools, run errands and carry out other tasks particular to the area they worked in. The starting wage in the 1880s was about 6 pence a day, which was paid monthly.
As they grew older and stronger the young men would be put onto specific areas of the works, for example in the pit or the dry.

Some types of clay work were paid at a price rate for the work done, such as the removal of overburden. This may have been at the same rate as the men's daily wage, and was often done by fit employees as overtime. In 1872 at Bloomdale works the men were paid 2 shillings and two pence for every cubic fathom of overburden cleared. The dry men were paid 8 pence for every ton of clay they dried.


6. Sand and Mica Drags

At Wheal Martyn the double "U" shaped concrete channels were used to settle out finer quartz sand. The flow of the slurry slowed down in the channels and sand settled to the bottom. Every two hours the drain plugs or bungs were removed and the "sand drugs" were scraped clean using a tool called a "shiver" (pronounced shyver). The sand ran through a drain to the river.
The slurry, now containing only fine china clay particles, fine sand and flakes of mica entered a series of wooden channels, called "mica drags". It flowed slowly, dropping mica into the floor of the channel, whilst the fine clay flowed on. As mica built up in the channels leather hinged flaps were raised to maintain a constant flow and to make sure mica was still deposit. In many works this was done by a manual system but these micas appear to be prototype for John Lovering and Robert Martin's patented "improved" micas of 1882. All three series of traps are connected by a rod controlled by a float in a sump at the lower end of the channels. Water enters the sump at a controlled rate from the barrel and the traps are automatically raised as mica builds up in the channel.

The mica was cleared from the channels using a shiver every eight hours. The wooden plugs or bungs were removed and the mica washed to the river. Some clay slurry escaped too, adding to the whitening of the St. Austell River.
Today all such waste materials are trapped by large lagoons or dams to eliminate pollution of the rivers. This waste contains much clay and old dams are often refined again.


7. Blueing House

Pure clay slurry flowed from the micas into the blueing house. The slurry passed through a wire mesh screen to remove leaves or other material which may have contaminated the clay. This screen was brushed clean by a heather brush which was moved by a small undershot wheel in the building. Sometimes blue dye or colour (such as ultramine) was added to the clay to improve its appearance and hide any discolouration.


Thickening the Clay

8. Settling Pits

From the blueing house the milky-white clay passed into one of the settling pits below the mica drags. These granite tanks had a sloping floor and could hold abaot 250 tons of clay slurry. The clay was allowed to settle over a period of several days. The clear surface water was progressively run off the pit side. Once the clay had reached the consistency of single cream, about 12% solids, a large plug was lifted up and the clay passed through earthenware (cloam) pipes to another set of tanks at the pan kiln.


9. Slurry Pump

As with many china clay works, Wheal Martyn was buiilt on a hillside to help the clay slurry move around by gravity. However, some settling pits here arel ocated above the mica drags and needed to be filled with clay slurry by a pump.

It is suggested that settling pits A and B are older than pits C,D,E and F (see map). They may have been fed by an older set of mica drags above the present refining area.
When there was a demand for more china clay John Lovering may have brought the pits back into use. In about 1902 he built the overshot water-wheel (4) and slurry pump to fill the pits with clay slurry.
The clay slurry was lifted by a bucket lift - a piston fitted with a valve which works inside the cast iron pipe. It can lift about 26 gallons (120 litres) per stroke.


10. Settling Tanks

There are five stone walled tanks here which were filled and emptied in rotation whith clay from the settling pits up the hill. The clay was left to settle until it was as thick as clotted cream. When the clay settled, clear water was run off the surface through pin holes in the hatch boards at the back of the tank.

It could take two to three months for the clay to reach about 35 - 40 % solids. At that time the hatch boards were removed and some clay ran through into the dry or pan kiln behind. To move most of the clay, rails were put down in the tank and a small muck wagon was brought out from the pan kiln. The wagon was then loaded with clay using shovels and ladles.

Women Clay Workers

Women were employed in the China Clay industry to carry out a particular task before pan kilns dried all the clay at each clay works. At first the clay was left to dry in a shallow tank called a "sun pan". The sun pan was lined with sand and as the clay hardened it was cut blocks were stacked in the air dry, a small open-sided structure where the clay was dried by the circulation of air through the building. The women were then employed at a daily rate to scrape clean the bottom and sides of each block. Two or three tons of day could be cleared in a day, and the women were paid about a shilling a day.

Sun pans remained in use into the 20th century; but as they were replaced by heated pan kilns the number of women clay workers fell.


Drying


11. The Pan Kiln or Dry

Once inside the dry, clay was spread across the floor of the pan kiln. The travelling bridge was introduced to ease this task; it could take wagons loaded with clay from any of the tanks to any part of the dry floor.

Inside the kiln, a series of horizontal flues run under the floor from the coal fired furnaces to the chimney, a distance of 220 feet (66 m). The floor is made of Porous "pan tiles" which allow the heat through. The tiles were made locally from china clay waste and sand.

Clay was spread 8" (20 cm) thick at the fire end and 6" (15 cm) thick at the chimney end where it was cooler. The pan tiles were thinner towards the chimney end, reducing from 5" (12,5 cm) to 2 1/2" (6 cm) to even out the temperature. It took a day for the clay to dry at the fire end and three days or more towards the chimney. As the clay dried it was scored into blocks, so that it was fully dry it could be cut with a shovel and thrown into the linhay below. This dry produced about 150 tons of dry clay a week.


12. The Linhay

The Linhay (pronounced "linny") was used for storing the clay until it was carried away to the customer. The clay was loaded onto clay wagons in blocks or packed tightly into casks. This linhay could store about 1,000 tons of dry clay.

Many pan kilns were built alongside a railway to enable clay to be loaded directly onto rail wagons. At Wheal Martyn the clay was transported by road, using horse drawn wagons and later lorries.


13. Electric Power-The Fal Valley Engine

After the First World War electricity was gradually introduced for pumping and lighting in the China Clay Industry. Each pit hat its own supply because mains electricity had yet to be introduced to the rural areas. In some pits gas engines were used.
The National Oil Engine and generator used at the Fal Valley Works of the Anchor China Clay Company was installed in 1928. It supplied power at 500 volts D.C. to the pit. It was started by means of compressed air from a small open type compressor driven from the main engine.


Transport

Every visitor to St. Austell in the last century seems to have commented on the transport of clay through the town; heavy wagons loaded or over loaded with clay trundling through the narrow streets of St. Austell on their way to the harbour of Charlestown. Moving the clay from the hills above St. Austell to the ports at Fowey, Par, Charlestown and Pentewan was a major problem and expense to the clay producers. It is hardly surprising that many schemes were put forward to build railways from the pits to the ports, including one unrealised plan at Wheal Martyn.

The real solution to the transport problem came with the introduction of pipelines to move the slurry directly from the pits to rail sidings or the ports before being processed and dried. Although first suggested in 1859 they were not used until the 1880s. Now almost all the pits are connected in this way, by a hundred miles of pipeline. Finally the invention of the steam lorry and the internal combustion engine helped those works such as Wheal Martyn which were not attacked to railway or pipeline.


14. The Transport Yard

In the transport yard, outside the linhay are a number of examples of transport used in the clay industry. Of special interest are:

Lee Moor Nr. 1.

Lee Moor Nr. 1 is one of a pair of identical locomotives built by Peckets of Bristol in 1899, to be used at Lee Moor Pit in Devon. Lee Moor Nr. 1 follows the usual practice for industrial locomotives at the turn of the century - apart from the 4'6" (1.37 m) gauge.

It has an 0-4-0 saddle tank with 2'6" (76 cm) driving wheels, two outside cylinders 10" x 20" (25,5 cm x 51 cm), working at 120 p.s.i., producing 6800 lbs tractive effort. A small tough locomotive, suited to it's bleak route on the Lee Moor Tramway, it worked well for 48 years, the left derelict for over 20 years before it was restored by the Lee Moor Tramway Preservation Socity.


Judy

Judy was built in 1937 by W. J. Bagnall of Stafford for work at Par Harbour. This standard gauge 4'8 1/2" (1,435 m) locomotive was designed to fit under a low bridge below the main line to Penzance. The success of Judy led to the purchase of a second identical engine, Alfred in 1953.

Alfred gradually superseded Judy who was kept in reserve in the engine shed for many years. Alfred continued to work until the end of steam at Par, in 1977. This engine can now be seen at The Bodmin and Wenford Railway near Bodmin. Judy came to Wheal Martyn in 1978.
These locomotives provided the inspiration for two of the Rev. Awdry's characters in the Railway Series of books; the twin engines Bill and Ben.


The Clay Wagon

This wagon is one of two survivors of the typical heavy horse wagon used by the clay industry in the nineteenth century. A few were used right up to the 1920s. These wagons could hold up to three tons of clay and were hauled by a team of three horses. More horses were added to bring the wagon up a steep hill.


Peerless Lorry

This lorry was built in the U.S.A. in 1916 and came to Europe to be used during the First World War. It was then sold as "War Surplus" and bought by a clay company, Parkyn and Peters, who used it at their Blackpool Pit. It was one of the earliest petrol engine vehicles used in the clay industry. After about 10 years it was discarded and buried under a sand tip. In 1958 it was rescued and put into store. Restoration work began in 1978 and was completed in 1982.

It has a 4 cylinder 6760 c.c. engine which produces 40 b.h.p., a maximum speed of 15 - 20 m.p.h. and five to six miles to the gallon.

Temperature: circa 20°C - mixed but warm weather

Driven miles: 90 = 145 km