Susan Mulroy Ceramics, Ceramics and clay workshops

 

The Rocket

I was really pleased to hear of the success of Ken's latest Rocket firing after finding some sort of rapport with what I'd always seen as an almost impossible kiln during the night stoking shift with Norman. Suitably inspired I suggested to Norman that the only way to get to grips with this kiln was more experience, and as I had an exhibiting opportunity coming up in September, maybe we could organise a private firing in August.

Sandy had shown an interest too, and three seemed a good number to fire this kiln, so we contacted Eric to get the ok, arranged wood (thanks Norman yet again), access to the site (thanks Peter) and sorted out wadding materials, etc. just in time to fire on 20th August.

We arrived at the site in the early morning armed with glazes, pots, a lot of enthusiasm and a little experience. Fortunately for us, Andrea supported our efforts as none of us had previously gone through the first 6 hours of firing and her help in arranging the pack and keeping the fire outside the firebox in good health was invaluable.

The agreed format for the pack was a small gap at the back, very loose back shelf, reasonably tight through the rest of the kiln, with pots on bricks at the front to make the most of the heat.

After a communal packing session, we sealed the top, took a deep breath and at 1pm, set a fire outside the firebox. I get scrap wood for kindling from a local firm and had brought 4 bags of tongue and groove larch cut into short pieces. This wood was great for the early fire. It built up a good ember bed and after 5 hours, once the black soot that had coated the inside of the kiln had lightened to grey, we moved the fire into the firebox.

The ember bed was so good that we had no problems transferring the fire from the base of the firebox to feeding the fuel in through the top stoke hole, allowing the proper circulation of air through the downdraft firebox. The front of the firebox was sealed, but following the success of Ken's previous firing, a mouse hole was left at the bottom of the door to assist in controlling the ember bed throughout the firing.

During the previous firing Norman and I had taken over just after the transfer of the fire into the firebox and had worked furiously, pushing the kiln by filling the firebox at every loading and riddling hard to encourage the air through the wood and ash to fly through the kiln. This had created a lot of heat at the firebox end, unfortunately that hadn't had time to radiate through the 'heavy' brickwork and hit the back end of the kiln so we had cone 12 flat at the front before any sign of softening in the back cones (lowest 7). Perseverance paid off, and the back cones had started to go - cone 9 just bending when Ken joined us in the early morning. Ken's light touch changed the rhythm of stoking, he stoked much more lightly, balancing the air and flame by constantly checking the back spy and the rest of the cones went down like dominoes, cone 11 down while the kiln still felt as if it still had plenty of power left.

On Ken's advice we changed tactics completely for this firing and followed his gentle 'little and often' policy through most of the firing. We let the kiln dictate the pace, just letting the natural hunger of the fire set our stoking rhythm, and gentled the kiln until the morning. We kept a close eye on the ember bed, never allowing it to disappear, but using secondary air through the two mouseholes whenever it grew and threatened to choke the flame path. The kiln seemed happy, showing a good temperature rise, and a lively, if gentle, fire in the firebox. The front cones went down easily enough - cone 11 was falling when we decided that the gentle, slower firing was still not achieving the required temperature in the back of the kiln so we tried to balance the flame to 'lick' the cold spot as Ken had. Whether our inexperience or the lower temperature was the cause, the cones were difficult to shift. We applied a more vigorous stoking rhythm and the cones started to fall, but with cone 9 down we came to a standstill again, and, as we'd been firing for more than 24 hours and seemed to be making no progress, we decided to call it a day. We'd just completed a session of oxidised firing and so shut the rocket down, and left with mixed feelings. The morning had seemed full of hope for achieving that cone 10 down at the back, but it wasn't to be, and to get cone 9 down was still an achievement. We decided that the kiln needed a firmer hand a little earlier in the stoking, we'd just been too laid back for too long. Generally the method worked well right up to the cones going down in the front, and we came away with a wealth of new experience to use in the future.

The results were mixed, the back a little dry as expected, but the loose pack there seemed to have helped, and there were some lovely effects from the front, particularly where we'd been brave with the packing and leaned dishes up against tall pots. All in all a fantastic experience, and one we can't wait to repeat, but this time with those back cones well and truly down. Its addictive this wood firing business.

 
 

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