In the Japanese pottery world, the word ‘tsuchiaji’, lit. ‘flavor of the clay’ is a much used term. In the case of Karatsu, even more so, though I wouldn’t be surprised if Japan’s long, rich history of unglazed ceramics is the main reason this term is so important.
Possibly the most distinctive characteristic of Karatsu ware is the clay, and one thing you might notice when looking at the ware is the lack of glaze on the foot. It’s probably safe to say that most potters (in the world) pick up pots and examine the foot first when viewing a pot, because it says a lot about the potter who made it. Most of the Karatsu potters and collectors I know do this, not just to view the carving job on the foot, but also to see the clay that was used.
The clays found in Saga prefecture, including the Kishidake area close to Karatsu, are usually quite large particle, non-plastic clays which contain a lot of sands. Lots of sandstone and coal throughout the area as well. Many potters (modern and historically) use sandstone in their clay body to seal the body, since many of the clays will not mature even at higher temperatures. Not only are many of the clays quite sandy, but in many cases the clay used was actually sandstone, not clay. One contemporary potter uses pounded sandstone for his clay body, and close examination of some old pots has shown that they too might be made of sandstone. One group of researchers travelled to Korea and found a place where similar practices had been utilized for hundreds of years (the name of the place escapes me now). These potters started with sandstone and pounded it in stamp mills. They then seived it into various particle sizes and created their clay body from that. Left over particle sized were used for other purposes such as glaze ingredients, making kiln furniture, etc… so that there was no waste, all of the sandstone was used.
Anyway, the most prized characteristic of many Karatsu clays is effect of ‘chirimenjiwa’ or crepe-like crinkling that occurs when the clay is trimmed soft. This effect is most obvious in the 3rd photo below, top left, in the 3 footrings made of a white, sandy Kishidake clay, from the Hobashira kiln.
In all of the photos below, the pots shown are quite old (400 years give or take). All of the clays have developed a patina over the years and are likely much darker than when they were first fired.
I was so interested in reading your posts – cherishing pieces as they age and crack is such a different take on how most of us view blemishes in clay. I am wondering about the porosity of the clay – but I suppose tea would be finished before it became a problem? I have a local body which I collect from the slurry dam at the cement works which is probably still heavy in silica fines and mainly kaolin but it throws well but at Cone 10 is still porous – I have always loved the outcome but I know it would never sell here where functional means non-porous, but your posts give me a new appreciation. I think I need to make some teacups for me!
Hi Lyn,
Actually it doesn't take much for the water to get in there. Porous here would mean that the cup might sweat a bit onto the surface on which it is set, actual dripping shouldn't occur. Even the sweating usually decreases and may actually disappear with use, as the pockets in the clay fill with minerals, etc. from the water. Interestingly, the old potters added the sandstone to the clay body to seal it. The sandstone melts and waterproofs the clay to a degree that wouldn't happen otherwise. Even so, the water still seems to get in there, sometimes between the glaze and the clay body, where they might not be fused all that well. The old style split bamboo style noborigama are notoriously uneven in firing.
That clay from the slurry dam you mentions sounds interesting. You could use it to make something nice for yourself, then one trick you could try is to add some feldspar to it in increments. Hopefully you would be able to find an increment that allows you to keep the 'look' of the clay while at the same time sealing to an acceptable degree for the customers. This is what I do with many of my clays when I fire to lower temperatures. The extra feldspar seals the body, and also shortens up the clay even more, making it harder to throw, but giving it much more interesting texture on the trimmed surfaces.
Have fun experimenting, and if you ever post pictures, please let me know.
Mike
Hello Mike,
Very interesting posts. I see you are building a kiln too. Are you trying to get all the materials for free?
Dave Pike
Good Morning Dave! I see you're up bright and early this morning. Yes, I finally decided to bite the bullet and build the kiln. I'm not trying to get all the materials free, but have had some luck getting my hands on some brick. Building the foundation and floor (and maybe much of the chimney)from the scrounged brick will go a long way to keep the brick costs down. I'll probably still need to buy around 1500 straight brick for the main chamber. You already know this, but building these things gets expensive fast, when you factor in the kiln cover, shelves, topcoat, etc… At least I think I'll have a good free supply of wood.
I still haven't been able to test that ash you sent me, but think I will finally get it done this next firing. The most difficult thing has been trying to decide on the best use of the ash, firing in a gas kiln and all.
Thanks for the comment,
Mike
Oh, PS: You interested at all (or have time)in coming down for the kiln workshop? I don't know if you've ever met Craig Edwards, but he's a really great guy, great sense of humor, beautiful pots, and very strong work ethic.