Although I dig a lot of my own clay, every now and then I find a bagged clay that I like, and use it for certain projects. Since getting the big wood kiln, I’ve done more of this, because I can blow a lot of clay in one firing, and wasting collected clays is a real waste of time and effort. Once I’ve nailed down how to fire the woodie, I’ll go back to my collected clays since my loss rate will be much less (or at least here’s hoping).
Shoko Todo in Ureshino has a couple of clays I like, one of them is called Karatsu Kishidake because the base clay in the formula is from the Kishidake area. It also contains a lot of very fine sand, which is something I really like. Still, I like to add things to bagged clay to improve it, and this is no exception. If a lot of fine sand is good, then a lot lot must be better, right? Perhaps not.
I started by adding about 15% of my own sand to the clay, and to my surprise it improved the workability, giving the clay more backbone. It also gave the trimmed surfaces more character.
For the next hump, I added about 25% extra sand. I should have known I was in trouble when I couldn’t even wedge the stuff without it splitting apart and having chunks fall out, sticking to the table more than the clay lump. When I started throwing the hump on the wheel, pots would split vertically as I pulled the walls, and I couldn’t get near as thin as with the 15% sand/clay mix. Most of the bowls I managed to finish still had rips in them that I had to go back and fix later. When trimming, this clay gave a very rough texture, and I really liked it, but not enough to go through the frustration of throwing the stuff again. Although, for small things like guinomi this clay is the bomb.
Below in the pictures are two trimmed feet for comparison. One is the 15% mix and the other 25%.