For Science!

[offcntr]

One of my colleagues at Club Mud, Shelly Fredenberg, does lovely, minimalist animal sculptures out of porcelain. The sort of pure, white, simple surfaces that just beg for elaboration by exotic firing processes. At least, to all the rest of us surface treatment fanatics.

Jon and Karen talked her into soda-firing. Tea wants her to try saggar firing. I promised I'd throw a couple of saggars, and figure it out with her.

Saggar firing is basically firing inside a closed pot, as a way to create a special firing environment in a controlled space. It's usually used at low temperatures in electric kilns to get salt glaze or reduction effects. Less often, it's done in high-fire kilns, which is where we're gonna try.

The plan was to nest the work in combustible material, probably sawdust, top-dressed with a little copper carbonate, and see whether we got black or red or white or some wild combination of all of them. Of course I discovered I was out of sawdust, though I did have a small bag of wood chips I'd bought for my sausage smoker. Fortunately, the research I did online--which all seemed to reference the same Byron Temple workshop--suggested that crushed charcoal worked even better, and I have plenty of that.


So yesterday we loaded up the saggar. Crushed charcoal first, about six briquettes, mooshed inside a doubled clay bag with the hammer and two-by-four I used to fix the kiln chimney. (It's a multi-tasker!) Then we nestled our treasures in place, sprinkled about a teaspoon of copper carbonate over the top, and then, because we were feeling a little mad-sciencey, a little bit of soda ash. The last ingredient is used in soda firing, where it vaporizes and makes a glaze with silica in the pot. We didn't use enough to make a glaze, but hope it might help the copper fume up and move around a little bit.

Lastly, we lined the top of the saggar with scraps of ceramic fiber, for a tighter seal, and pressed the top in place. Today, I'll put it in the glaze kiln, and we'll see what happens.