Visit to Wheal Martin Clay Mining Museum

We spent a few days in Cornwall. We arranged to meet friends in St Austell and while there, I began to realise that the town was associated with clay mining. Our holiday preparations are never very comprehensive. We partly went to Cornwall because of all the clay related things to visit, but that was as far as preparations got. Still, we were lucky, as this map in the town encouraged us to take a visit to the "China Clay Country Park and Cafe", which turned out to be absolutely fantastic. It was good for children (4 to 7 year olds) and adults; and completely absorbing for anyone interested in the ceramics industry. We can't recommend it highly enough. Here is the link to the Wheal Martin museum and park. Below is some of what we saw.

The map in St Austell which lead us to Wheal Martin

At the car park and museum entrance
The mines and pits in this area are for china clay. This clay is very white when fired and is the basis of porcelain and other white clay bodies. These lovely statues at the entrance to the museum and park reflect this in their whiteness.



It took me a little while to realise the museum tells the story of how china clay is won backwards. This is because a lot of the original workings are situated outside, climbing up a hill. The entrance to the museum is where the cleaned china clay would have been dispatched, at the bottom of the hill. That layout just reflects the process - washing the clay from the hill above down towards the bottom via various settling and drying pans. This post walks us up the hill too.

One of the many disused pits in the area. This is at the car park at Wheal Martin 
China clay is called, by potters at least, a primary clay. It is decomposed granite and hasn't moved position by water or wind erosion, as is the case with secondary clays, and so remains very pure. Notably, it hasn't picked up lots of iron causing it to fire to a brown colour. So china clay sits where it was created in amongst granite pieces and can be washed out by water. By the 1920's they were blasting the rock with water canon.
Water cannon,  known as a 'moinitor'
Monitor
As pits were dug the water-blased clay slurry had to be pumped from the bottom of the pits to settling tanks, to separate the mica and granite stones from the clay. Plunger pumps like this below, were developed by Richard Trevithic for the tin and copper mines in Cornwall.

Plunger pump
Pumps were powered by water wheels and later steam, while today it is probably diesel or electric. Below is a fantastic pitchback water wheel, used to power pumps between 1884 and 1940. It was fully restored in 1976.


Exhibits inside the museum
A lot of the exhibits here show some of the way clay was processed and used, not specifically to do with the china clay industry.


When clay has been blended in mixers it is very wet. This is a press which squeezes the water out under tremendous pressure.
The grey box is a potters wheel, hand turned by an assistant. The big wheel is a fly wheel for belt driving another potter wheel 
A hand turned potter's wheel
Another hand turned potters wheel
Sieve for glaze materials. The brush pushes the wet powders through the sieve, making sure all the materials are evenly dispersed

Different types of bricks made in Cornwall
This is a clever plate rack to allow plates glazed all over to be made. The plate are supported on 3 metal spikes, which leaves just a small mark on the glaze. The rack means the plates can be fired close together in a kiln. Plates take a lot of space in a kiln without this type of system - they would be stacked on individual shelves. Alternatively they could be made with unglazed rims and footring and stacked face to face and foot to foot.
Plate rack for glazing
Various country pots
Pancheon and ... well I thought at the time this was a urinal.. Now I'm not so sure.
These ladles were used when china clay was too wet to stay on a shovel.
Coming out of the covered museum and into the open air

As it happens, this open air museum is great for visitors of all ages!



Apart from storing and distribution of the china clay, the shed below was the last part of the process of winning china clay. As mentioned earlier, the visitor's walk through the process of winning china clay is backwards. So bear with us - it eventually makes sense.

Once the china clay slurry had been separated from the other unwanted rocks, it needed to be dried, which is difficult in Cornwall's damp climate. Sheds with underfloor heating were introduced. The pure china clay slurry is spread over the floor and then cut into liftable blocks when it is drier to remove.
Pan kiln, locally known as 'the dry'
The pan kiln shown above is the shed seen below. In front of it is a the final settling tank before it goes into the pan kiln. Incidentally, the hill in the background is man-made. It is a tip made from the gravel settled out during the china clay mining process. 
Settling tanks, with pan kiln sheds attached

Working water powered pump
Working water powered pump
Before the settling tanks next to the pan kiln were these settling pits. At this stage the china clay is pure and it just remains to get the water out of it. These settling pits were granite lined and as the clay sank to the bottom, the water was drained off the top. When the clay was cream consistency, it went to the settling tanks.

Settling tanks - pure china clay, removing water
Before the settling pits are these "drags", designed to remove mica sand from the mix of china clay and water. The troughs slope very gradually, so the slurry moves slowly through them allowing the sand time to settle out. Only water and china clay flow over the top of the end of the trough. The drags had to be cleaned of sand around every eight hours. It was washed away down into the river below and then to the sea.
Drags for removing sand

Below is the mouth of a tunnel, called and adit or level, which carried clay slurry from the mine face to the settling tanks further down the hill.
Adit or level
Another tunnel was used to pass the drive rods (called flat rods) from the massive water wheel at the bottom of the hill to pumps further up the hill and to the clay pit itself. 

Flat rod tunnel

The modern pit

It isn't a long walk to the top of the hill, but it is certainly worth it. The old mines have gone - but only because they have been mined away. This is what we come to.




Driving away from the museum and around St Austel, the landscape takes on a new meaning.