Kiln Building: Part One

In March of 2025, I returned to Wytham Woods to take part in a kiln building course lead by Master kiln builder Claude Aussage. This time, I felt a little more confident returning to the site having spent a week there in September, and it felt familiar to walk the path up from the car park, past the giant wood piles over to the kilns.

Meeting everyone partaking on the course was a real pleasure, but I was most glad to see my friend Jack Smith, with whom I had stoked the Svend Bayer kiln from 2am - 6am back in September.

Claude spoke to us initially about the role of a kiln designer/builder - which is to fulfil the client’s requirements. For these kilns that we were building there were numerous specifications. We were to replace the three existing fast fire kilns. And by fast fire kiln I am referring to a small, top-loading, down-draft, wood-firing kiln than can be fired in a day. I won’t go too much into the specifics, as there are much better resources available. These kilns are sometimes referred to as ‘Philosopher’s Kilns’ ( see the book by Steve Mills) or ‘Olsen Kilns’ after Fred Olsen, though I actually think the one we built was not quite the same as the Olsen design.

The first job was to take down the existing kilns and analyse them - what information could we glean from looking at how they had deteriorated or been damaged. How did they compare to each other and what did the firing records tell us about their performance? We split into three groups and dismantled these three kilns, preserving as many bricks as possible in the process - we were lucky that the majority of the soft bricks were still in a usable condition.

Once the kilns were dismantled, we set to work rebuilding. My group was made up of 6 - myself, Jack, Dan, Yi-an, Philip and Amy. All very enthusiastic, hardworking, skilled and knowledgable people which made me feel confident in our task. We moved the position and orientation of the kiln so that the two kilns would be facing opposite directions, we considered how this might impact firings and thought that it might encourage groups to be more intuitive when firing these kilns together, as opposed to copying the other kiln’s schedule.

We resurfaced the area so that it was level and laid breeze blocks for the base. Then the first layer of bricks was laid. The structure of the kilns consists of a firebox made of hard refractory bricks, grade 42 or higher, mortared together with a mixture of fireclay and silica sand. Laying these bricks became really satisfying once we developed a rhythm of dipping the brick in water, passing it to the next person to apply a layer of mortar and then passing it to the next person who would lay and tap it into place.

At one point, Ekta came along and advised up to straighten up the walls of our firebox, which from her angle she could see were a little bowed. Once the firebox was built, we then proceeded to add kilns shelves for the floor of the ware chamber (or roof of firebox) and then began the layer of soft bricks. We had a few calculations and adjustments to make when it came to the chimney, as the kiln shelves added extra height which we then had to cut off from the support bricks. We also had to make sure that the flue was large enough, as the previous kiln had a slightly smaller flue and was reportedly harder to fire. Additional design element we included were two extra mouse holes towards the back of the kiln and a hole to introduce ash via a ‘glitterspritzl’.

And that was it! Once the chimney was built, we simply had to add the thermocouple, pack the wares and close up the kiln the ceramic fibreboard lid. It took us under three days to fully dismantle and rebuild the kilns, and so the only thing left to do was fire them.

Our group decided that we wanted lots of reduction and lots of ash in our firing. As this was only my seconds wood firing experience, I should have felt less confident but something about having built the kiln ourselves put me at ease. Plus, we were in the presence of the fantastic Claude, who is overflowing with valuable knowledge and has a incredibly relaxed attitude to the whole process which can only be acquired through vast amount of experience.

The firing was successful, we used a lot less wood than we had anticipated and we were able to unpack the results the next day,