Friday, October 12, 2012

Cone 6 'electric glaze' fires nicely at 10-14

I've been introducing a cone 6 electric fire glaze into the wood kiln for the past several firings with some interesting results. This last firing produced some nice purple and yellow. I know the purple is from a reduction atmosphere in the kiln, starving the kiln of oxygen so that carbon is produced. That's probably a simplistic explanation of reduction. But I'm not a chemist.

The yellow was a suprise. I hadn't seen it before. Levi glazed quite a few of some small cups and vases with the cone 6 glaze for this firing, and we had it throughout the kiln, from the front to the back. We reached cone 14 in the very front of the kiln, and cone 10 in the back. Many of the pieces were brushed with red iron oxide underneath the glaze. I'm thinking the red iron helped produce the yellow.

The glaze is a copper carbonate glaze with a small percentage of lithium as an ingredient. It's a recipe from Richard Zakin's book on electric kiln glazes.

When firing atmospheric kilns, it's recommended to keep a log of each firing. Well, I did a poor job of logging on this firing. However, there was a point when I put the kiln into reduction by opening up passives in the chimney, which I do for most of the firings. What we did do for a period of time, was allow the build up of embers in the firebox without pulling a brick in the air intakes to allow more air into the firebox. I'm thinking this caused some heavier reduction than usual.

Here's a couple of examples:

Thursday, October 4, 2012

Sneak Peak - will unload Saturday

Six-foot flame exits the chimney after the last stoke
Wednesday's wood firing went well - a 14-hour affair from start to finish with the first hour being a little propane warm up.
Now, we wait. Well, there's a bit of peaking in through the passive dampers where cool air is unlikely to rush into the ware chamber and crack pots. I suppose I should share a couple of pictures, huh?

We took the temperature up slowly for the first 1,000 degrees or so, as I had some shelves that were a bit wet from applying kiln wash (a mixture of kaolin and alumina that keeps glaze drips and ash from totally melting into the shelves) and I had those very large soul pots that I didn't want to stress out too much.

We reached cone 9 in the bottom of the back of the kiln, the usual cone 14 or more in the very front.

We will open up the kiln to the public at 9 a.m. Saturday during our annual R.D. Mahan Kiln Opening and Turkey Roast, Oct. 6 and 7.

A Levi vase with copper glaze at the back of kiln
Pitcher with flashing slip behind cones