| Celina’s blog “On ceramics”: Unloading a Anagama kiln |
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Unloading a Anagama kiln
Yesterday, while we were at our work, one of the teachers came to our class to announce that the “Kaneyama” kiln, at the Shigaraki Ceramic Park, was scheduled to be unloaded early afternoon. They asked for help. So it was decided for us to go there.
It was not the first time for me: four years back, I had the opportunity of watching the process of firing this huge kiln and took these photographs.
 The Kaneyama kiln, a kind of legend until a few years back when its ruins were discovered nearby the town of Shigaraki. It was replicated inside the Ceramic Park.
“Anagama” type of kilns have the shape of a tunnel half-underground placed along the slope of a hill so the mouth is in the lower part while the chimney is in the upper part.
 To fire this kiln it takes about five days before all openings are closed and it is let to naturally cool down for more or less equal length of time.
I would have liked to show a general view of the kiln but it happens that it is blended into the ground and only the feeding mouth is visible from outside.
 It was a rainy day but anyway, they decided to unload the kiln.
When we arrived in the place, men were already busy collecting the un-melted ash for use in the dosing of glazes for next firing.
The most traditional Shigaraki ware is not glazed but with the melted ash that wood fire produces. Wood ash melts at higher temperatures than 1250˚C and the kiln is fired to more than 1300˚C near the mouth.
It has a central wall, as shown in the following Prof. Takahata photography and its length develops along more than 12 meters. It has only one feeding mouth and the wood has to be thrown inside as deeply as possible for a dexterous thrower, an specialty among a few needed when firing it.
For this reason it is unavoidable that the first line pots are often broken under the strength of the impact.
Ash glaze color depends on the atmosphere of the firing: nearby the mouth, oxygen is scarce so the color has dark variations, these depending on the composition of the wood used as combustible. But near the chimney, when the damper (air current) is stronger,
deep sense of solidarity: they are aware that any time, one will need the help of the others
and that only together can not only survive, but also achieve their goals.
 
Technical:
High temperature sensors called thermocouples (six to eight for this size of kiln) are introduced inside the kiln and a digital device plots its variations; each thermocouple in a
 different color. While for an electrical kiln a continuous line is obtained, this meaning that temperature rise is very stable, a wood kiln shows zigzag-like lines: each peak registers the frequency of the combustible feeding and the space between two peaks is determined by the length of time left in between each two. It is clear and obvious that in this kiln there is a difference of about 200˚C between the hottest and the coldest area inside. In old times, when no thermometers were available a highly valued specialist in judging temperature by the color of the fire was needed: dark red when it is about 800˚C, whitish orange when is over 1250˚C. To decide the end of the firing was a very crucial judgment as it could determine the success or the failure of the firing.
Copyright©Celina Clavijo Kashu2010 for Forum Artistico
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