Jingdezhen in China has a very long history of making porcelain. Over one thousand years in fact. They had already celebrated their millennium of porcelain making when I was working there ten years ago. The special thing about this place is the clay. It isn’t clay!
What they use here is a ground-up stone. When they crush and finely grind the local stone down into a very fine paste, it becomes plastic. This is like magic. Stone doesn’t usually become sticky and plastic like clay unless it’s very special. This stone is largely composed ofsericite mica, and it is special. It is reasonably rare stuff to find en-mass, in its pure white form. It has a flat plate-like crystal structure, not unlike clay, only much coarser. When these microscopic plates are wetted, they slide about against each other in a similar way to the way that clay does. Of course it’s so much more complicated than that, but this is a blog and not a treatise. Sufficient to say that there are very few places in the world where this kind of thing can happen. Here in China is one of them and the initial place where it was first discovered. Once the knowledge was well-developed in china, the information spread to Korea, where they discovered and developed similar materials, then eventually to Japan. When the War Lord Hideyoshi invaded Korea and brought back potters as war trophies!. My, how the level of respect for potters has fallen! I don’t recall any solder capturing and bringing back any potters as trophies from any recent wars that we have been engaged in!
One of these ‘renditioned’ Korean potters discovered a similar weathered stone on the southern Japanese island of Kyushu, and so porcelain making started up there as well. I have visited these sites and made pots there and I intend to go back again and make a more substantial body of work there, just as I have done here in Jingdezhen, that I can bring back and exhibit all together back in Sydney. Hopefully at Watters Gallery.
My interest in these porcelain stones is all based on the surprise discovery 15 years ago, when I stumbled upon a very small deposit of pale rock in the side of a track, out in the bush. I collected a very small sample and crushed it down to dust so that I could test it for use as a glaze ingredient. It made a lovely pale blue glaze of the family of glazes that could be described as being like ‘celadon’ or ‘guan’. These are ancient Chinese archetypes of fundamental combinations of simple ingredients. They are the simplest of glazes, but just about the most difficult to re-create with the depth and subtlety that the Chinese potters achieved at the apogee of their ceramic development, during the Song Dynasty.
I recognised that my initial glaze tests, although crude, had potential to be developed into something special, but more than that I noticed that most of the tests were ‘crawled’. This would normally mean that there was too much clay in the recipe, but this recipe had no clay in it at all. It was just hard rock. Very hard rock. I had to use my jaw crusher, disc disintegrator and then 16 hours in the ball mill to grind it down to a fine powder. I asked myself. “How could such a hard rock have any plasticity. Does it have any plasticity?” I quickly ran to the pottery and mixed a little of the precious powdered rock dust with some water and worked it up in to a paste, then proceeded to try to throw it on the potter’s wheel into a small bowl form. It could just about be done. It was rough and misshapen, but it was a bowl. I fired it and to my astonishment, it fired into translucent porcelain. I coudn’t have been more surprised!. 100% rock dust and water became white, translucent porcelain!
I know the date that I did this experiment, because I scratched the date into the bottom of that first pot.
After 25 years of fossicking around this shire. I had finally found something really exciting and with a lot of potential to carry my work forward for a long time to come. So here I am in the clay making facility in Jingdezhen. The home and origin of single stone porcelain. They don’t do all the production here anymore. Some of the large machines sit idle now. It seems that they only do the final stage of blunging (washing) the clay into a slip and sieving it through a very fine mesh to remove any unexpected rubbish that may have crept in during transport and storage. This ensures that there will be very few ‘iron’ spots in the finished product. The liquid clay ‘slip’, is then pumped into a filtering machine to de-water it back to a plastic, workable state. This de-watering procedure is called filter-pressing. This filter pressing (stiffening) is done in very large filtration dryers until it is ‘plastic’. ie. stiff enough to fashion into shapes, by moulding or throwing on the potters wheel.
Once the clay has been stiffened in this way, it is dropped out of the filter press and is taken to the extruder, to be pugged into well mixed sausages for storage and ageing.
The ‘clay’ (milled stone) material is trucked-in as a partially processed material these days. It used to be all processed here, but now it undergoes its primary crushing, milling and stiffening out-of-town, closer to the mine. When I was here last, all of the crushing was done by water powered, wooden hammers. these were typical of the water hammers that are to be found all over Asia, where-ever there is a suitable stream and work that needs doing. The powdered rock dust was then slaked in water and left to sit and dissociate, allowing the water to penetrate into the flakey, plate-like structure of the mineral. Breaking it down into a slurry with enormous surface area and also allowing the local bacterial to colonise the surfaces and work their magic to help enhance the workability and plasticity of the finished ‘clay’. This thick slurry was then stiffened slowly in the air and eventually formed into little white blocks or bricks called ‘bai-tunze’, or ‘white brick’. This is the form that it was delivered to the pottery clay processors.
But that was then and this is now!
Apparently the water hammers were working here up until last year some time. Due to pressure to increase production and through-put, these ancient water hammers were ripped out and the leats that brought the water were filled-in and concreted over. 3 phase power has arrived now and all the work should be being done by jaw crusher, huge ball mills and filter presses. but when we arrive, we find the place devoid of activity. The power is down and has been all day, possibly yesterday also. and who knows when it will be restored? A lone woman sits by idly and bored and waits. Perhaps the old water hammers had some advantages? They may be a bit slow, but they ran for free and all day and night as well. So why no both?
Jingdezhen native sericite stone.
This stuff is beautiful to work with, fine and smooth and so much more plastic and supportive on the wheel. I like it a lot. Of course my stone isn’t semi-plastic sericite, it’s just plain old hard, weathered, aplite. A quick cooled acid rock. It doesn’t become very workable without a lot of effort and time applied. However, I have found that after 6 years of storage in a cool dark place, it comes out not too different to the fresh stuff from Jingdezhen. I just need to buy some time! Time is the most expensive ingredient in my work.
from the patient and timely Old Rocker