Clay and Fire, Part I

Why would anyone want to go to the trouble of firing a wood kiln-the firing can take days of constant attention and fire-stoking when they could just use an electric kiln that you can program to do all the work? Wood kilns are not common, many ceramic students and artists never get the opportunity to find out. In October, I had the amazing opportunity to help fire a wood kiln. I even got the honor of lighting the right side of the kiln. I knew something about the process before I had he actual experience; the fire surrounds the clay and deposits ash on what is being fired, creating serendipitous effects that simply can’t be achieved in any other way. But there is also a community aspect, and yeah, it’s somehow embarrassingly satisfying to play with more than two thousand degrees of fire. ​

Right, AnWirthiemdrew Storck, me (Cindy Vojnovic) and left, Ellie Wirthiem, after rebuilding the firebox of the old kiln

Between Covid and a groundhog undermining the kiln, the old woodfire kiln hadn’t been fired in years. Luckily the groundhog had vacated the premises when Andrew Storck and I took on the task of rebuilding the firebox. This is not something I would have attempted on my own, but I was keen to help because that’s the best way to learn about the kiln construction-to literally rip it open and see how it works. Unlike store-bought kilns, wood kilns are built as one-offs, and whoever built it has many choices to make. We had no idea what we were getting into, or how long it would take. Ellie Wirthiem joined in and we got the firebox of the kiln taken apart and put back together again faster than any of us anticipated. It was such a great feeling-glad I took a selfie to capture that burst of joy. 
However excited we were at getting the old kiln back together again, we had no idea if our modifications would work, or not, or if there were other problems with the kiln from sitting for years unused, so it was decided not to make the changes too permanent and to do a test firing. Another factor was that in the past, that kiln had never been fired hotter than cone 6, which is about 2,200 F. A new wood kiln is under construction that is designed to go hotter, to cone 10 which is 2,385 F. That might not seem like a lot, but once you get to a certain temperature, it’s really a struggle to get a wood kiln hotter. Also, a clay “body” (recipe, if you will) that works at cone 6 could warp or even melt into a puddle on the kiln shelf at cone 10. In fact, testing clay for the cone 10 wood kiln environment was a compelling reason to fire up the old kiln. That way, once the new kiln is completed we have a reliable clay recipe to use in it. 

Me, mixing up the first batch of Body A "garden gold" cone 10 clay-photo by Kelly Allen

Walter Heath, who is the alchemist behind the clay getting mined and processed from the East 40 in the first place, came up with 2 recipes to serve as a starting point for a cone 10 clay body. They both featured what we call the “garden gold,” the local clay mined from the East 40. While I had no previous experience firing a wood kiln, I do have experience mixing clay, so I was happy to take on that task. There are machines specially made to mix clay, which I had used in my undergraduate days when I worked as a paid assistant in the ceramics department, but we don’t have that machinery so I just used a sturdy tub and a powerful drill with an agitator attachment, for want of a better way to describe it. Without the heavy machinery, you can’t mix the clay with only the amount of water needed for the finished clay; you have to add lots of water and so end up with smooth, nicely mixed clay soup. After hydrating for at least a couple of days, the soup (called slip) has to be poured out onto water-absorbing plaster slabs to get it to a workable consistency, so the clay-making is at least a 5 day process. 

The first form I kept, thrown from "Garden Gold" A body, see next post for how it came out of the wood fired kiln!