Thunder Train

We’ve had a busy couple of weeks here at Mill Creek Pottery. In between listening to Roald Dahl audiobooks in the studio and impromptu jam nights, we somehow fulfilled the mammoth task of loading and firing Simon’s ‘Thunder Train’ kiln. Though more of a Big Friendly Giant than the name suggests, it has a sizable, but not unmanageable tunnel chamber, measuring in at a little less than 1.5 cubic metres of space.

The kiln is packed from the door on one side, unlike the toploading bourry box built by Robert Sanderson at Guldagergaard, one I fired last autumn. This design makes it more of a challenge to load (but not so bad for someone fun-sized like me) although the fixed roof is a bonus as that one in Denmark could take a long time to assemble well. We placed in three stacks with two side stoking holes in between. Simon had a great hack for getting the last couple of shelves up in the middle, where the arch of the door blocks the way. We slowly raised the shelf up using some chunks of two by four lumber and a manual scissor lift.

First Thunder Train firing - beginning the firing in the firebox ‘clean out’

Sliding door to the main chamber of the firebox on the opposite side

As with most firings this size, the effort was collaborative and we were joined by Emily Wheeler and Lars Voltz, ex apprentice and self styled muck maker and wood melter. Thank you both for making a fun team! The kiln was also host to a few hundred tiles, the beginning of our commission for Forrest Lesch Middelton (FLM Ceramics). We lined each shelf with these before stacking pots on top to encourage flashing and wadding halos. Like with the anagama firing back in Wisconsin in July, Simon uses a red and a white wadding. However, unlike Susanne Lukacs-Ringel, the German potter I worked with, who has specific waddings for specific clays, Simon’s approach is more of a mix and match - using red wadding on porcelain for dramatic effect rather than trying to hide the marks.

After the second day of packing, we lit the kiln on Saturday the 25th. Beginning in the ‘clean out’ hole at the base of the firebox, we stoked in small pieces of pine until one cone 06 (approx 1000C) was softening at the front with the pyrometer reading around 1150F (621C), then transitioned to the main firebox. The initial climb of 100F/hr works out at a little more than 50C/hr. Firing in an alien temperature scale is perhaps a good exercise for learning not to rely too much on the electrics and to focus instead on the more accurate heat work readings of the cones. We didn’t end up doing body reduction cycles for each stack, I wonder how much this actually affects the final results.

One of the surprises of this kiln for me was how seldom it needed feeding once it got up to temperature. Being used to hungry anagamas, train kilns still feel pretty novel. They work on the downdraft principle, the fire burning upside down as the flames are pulled through by the draft of the tall chimney.

Once the transition was made to the main firebox, we piled in logs perpendicular to the metal grate on the inside, at first just a few during the transition phase and then more by the hour until the chamber was completely filled with each stoke. The gaps between feeds got longer over time, stretching from about 25 minutes at first then up to 40 minutes towards the end of the firing.

That’s not to say that we were idle. Side stoking began about 14 hours in and continued throughout the firing with regular stokes of small softwood every 5-10 minutes. And despite the regular snacks, Thunder Train had a big appetite at feeding time. The firebox can hold a lot of wood and each stoke ate up about half a big wheelbarrow full of mixed logs - iridescent walnut, oak, pine, Osage orange and the occasional rippling cut of curly maple.

First peek post-firing - Cones 10 and 12 still standing

44 hours in, once cone 9s were down at the back, Simon capped the chimney and Lars and I began the downfiring process. In order to create colourful flame flashing on the surface of the clay, it’s necessary to oscillate between cycles of reduction and oxidation as the kiln cools slowly. This is done by introducing small strips of softwood into the two side stoking holes until the bricks of the far side kiln wall are hidden by the flame fog. As soon as it clears you stoke again, alternating between middle and back. It’s a case of little and often with stokes every 2-4 minutes. This time we side stoked until midnight, just over six hours of toing and froing, the final reading at 1737F. Often Simon downfires until the pyro reads 1612F (877ishC) to get brighter reds. While firing with Yuichi Romita in Denmark we fired down even further to 1400F (760C). It is time consuming but not a large expense of extra wood.

The results were great. I’m not prepared to share too much of my own work at this stage but I have a lot of feedback to bounce off. I like the warmth of the sculptural clay and want to work at getting control of distracting throwing lines.

Currently I’m sanding Simon’s pots which will be on sale through Artstream Nomadic Gallery at NCECA (National Council on Education for the Ceramic Arts) next week - come check them out if you’re there, there are some beauties!

Elin HughesMarch 9, 2023