Tag Archives: kohiki

Kohiki tea cups, etc…

When Nishioka Koju passed a few years ago, a friend of a friend got some of the warehoused clay from one of Koju san’s storage areas. I was  able to get about 60kg of raw dry clay and have been waiting for the right opportunity to use it. I tested it a couple of years ago in the gas kiln and decided it needed wood to really make it jump. The clay itself is a light grey, almost white when dry, so I thought it might be fairly low in iron, but tests showed it to have significant iron and not very refractory. Probably good at around cone 6.

I made a run of about 40 cups yesterday and trimmed them this morning,  then waited for them to firm up a bit. Then, in the afternoon I applied the white slip (kohiki). This was something I have never done before on wet greenware. Last firing I tried it on dry greenware with success, but that clay was different and pretty stable for raw glazing. This clay is quite different so I didn’t know what to expect.  Many sources say to slip the inside, then let it dry, then slip the outside, to prevent the pot from collapsing. The problem with this is that you end up with too much slip around the lip of the pot, and more work is required to clean it off. I decided to apply to the whole piece at once, and did just one test piece to see what would happen. After 30 minutes the pot was still in one piece so I went ahead and did the whole group of 40.

I really like what the slip does on a wet pot. There is a lot more flow and variation in thickness, and I suspect better adhesion too. After the slip dries I will do some brush deco and give them a thin coat of clear.

At the end of the hump, there was enough left for a teabowl, so I threw one. It is intended to be a Todoya style Korean bowl, but we’ll have to see what happens in the firing. At least, this clay trims real nice. Unfortunately the bowl would not hang on to the trimming chuck, so that is the reason for the abrupt end on the interior of the ring. So as not to end up with nasty chuck rash, coupled with over trimmed foot syndrome, it got left as is. Usually trying to fix something like this just ends in disaster…