Firing the wood kiln at the NCC East 40: Part 1

Cone packs that will measure the "heatwork" achieved insidethe kiln at various locations

A delightful part of my part-time job as Manager of Ceramics at the Northampton Community College (NCC) East 40 is firing the wood kiln there! I had fired that kiln a number of times before, but for this Fall’s firing, I took on more of the work than in previous firings. I made the cone packs, for example, and made more of them than we had ever used in a single firing. Cones are scientifically formulated to bend over at very specific levels of “heatwork.” Heatwork is a matter of both time and temperature. The example I always give is lasagna. The oven may be 400 degrees, but if you only leave the lasagna in for five minutes, it’s not going to be cooked through! On the other hand, even if the oven is only 350 degrees, if you leave it in for 40 minutes it’s probably going to be fully cooked. Cones measure to what degree the ceramic is “cooked,” much like how a meat thermometer measures the temperature of the meat itself, not just the air in the oven. ​

The kiln fully loaded. Note the two fireboxes below the "ware" chamber where all the work is stacked, and the cones placed on various shelves in the kiln. There was a cone pack for almost every shelf, so we can tell afterwards how hot each region of the kiln was

It was the first time I actually got to load a wood kiln, which takes a surprising amount of skill, not to mention hoisting really heavy silicon carbide shelves into place. All the hours I had spent watching others load wood kilns was invaluable. The idea is to understand how the flame moves through the kiln, and much like playing pool where one ball bounces off another, you want to bounce the flame onto all the pots, ideally send the flame everywhere, reaching every pot without restricting the path through the kiln. No pot can touch, or even get too close to touching, yet you have to do a kind of Jenga where you get as much work into the kiln as possible. The way ash moves through and lands on the work is another consideration. Suffice it to say it was an honor, and I was holding my breath that certain decisions I had made would work out! For example, Kelly Allen noted that no one had ever put the center shelves as far to the front as I had. Yikes! I was hoping for better flow through the kiln, more ash, but what if it just meant that the work closer to the front door didn’t get hot enough? Gulp. ​

Door with all the bricks in place, including the one at the top center of the arch that I fitted

Nothing like a handful of wet clay in the freezing cold! Me at left, Gabriella Gentile at right

The door for the kiln gets built for every firing! First, the bricks. I actually really enjoyed custom fitting the last brick at the top of the arch, you can see it’s a lighter color than the bricks next to it. In previous firings we had done two bricks that stick out beyond the others, so you could remove them and see the cone packs strategically placed in the kiln for that purpose. For this firing, in addition to the two “peep” bricks, a third one with a hole in the middle was set up as a “blow hole.” Long story short, when flame is no longer coming out of the blowhole, you know it’s time to stoke. After the bricks were in place, Gabby Gentile (professor at NCC) and I “mudded” the door, which is pretty much like it sounds, although we used wet reclaim clay, not the kind of mud you have in a garden. Nothing like hands wet with “mud” in the winter. Then, for extra help so not so much heat escapes from the “door,” a special high-temperature cloth that looks like cotton but is not flammable, supported with a wire mesh was placed over the door. The pots were all loaded, the kiln was ready; but we had to leave it like that for weeks waiting for the burn ban to be lifted. ​