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 Feeding the Beast
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The scream of chainsaws echoing through a pine forest in Horokiwi signalled the first step in preparing for the 6th firing of the Wellington Potters Association’s Te Haunui Anagama kiln scheduled for 17-21 March, 2010. This will mark the 6th anniversary of the commencement of the anagama project in March 2004 and the 4th anniversary of the first firing in March 2006.
Graeme and June Houston, on whose property the kiln is located, continue to provide unstinted and vital support for those involved in preparing for the firings and in the firings themselves.
As the origins of the kiln and the first firing are well documented on this site, I’ll confine myself principally to recounting, in a firing log format, some of the significant details of the firings and associated activity thus far. Most of this information is derived from articles published in the Wellington Potters Association’s newsletter written by Richard Stratton, Ranae Palatchie, Vivian Rodriquez and myself.
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Dates
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Firing Master
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Comments
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1
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18 – 22
March
2006
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Shige Ohashi (Anagama kiln designer. A talented potter and veteran of some 50 firings of wood fired kilns in Japan. Worked for IBM in Japan before emigrating to New Zealand.)
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Fire wood split by hand.
Inaccurate pyrometer readings prompting very energetic and anxious stoking.
Unable to get temperature up to approximately 1300° C at the back.
Firing duration: 85 hours.
Participants reasonably satisfied with results from what was essentially an experimental firing.
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2
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14 -19
November
2006
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Richard Stratton (Ceramic artist and graduate of Otago Polytechnics ceramic’s course. Instigated the building of the anagama kiln.)
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Wood prepared using hydraulic splitter – a most welcome advance - bought especially for the club’s use by Graeme Houston.
The kiln was modified by moving the “sutema” wall slightly toward the back of the kiln.
Some 40 people contributed pots.
Aims of the firing: Get a greater ash build up than in previous firing and increase temperature at rear of chamber.
Using gas to pre-heat and dry out the kiln, the kiln reached 280°C in 15 hours. Switched to wood and continued firing for 110 hours until the ash glaze was dripping off the shelves.
The addition of a temporary Bourry Box in front of the wicket reduced the ember build up in the main chamber and assisted in achieving a temperature of in excess of 1340°C at the front. With the use of side stoking cone 9 and cone 10 were reached at the middle and back of the chamber.
Slightly improved results were achieved. More to learn about the kiln.
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3
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20 – 23
November
2007
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Andy Hope
(Major contributor of bricks to the kiln.
Studied ceramics at Otago Polytechnic.
Participated in anagama firings in Japan (where he lived for 5 months) and the USA.
Twice worked at Barry Brickell’s Driving Creek pottery in the Coromandel.)
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Two major technical changes were made to the kiln for this firing: the “sutema” wall was modified and a new firebox was built by lowering the floor of the existing firebox creating a pit in which a latticework of bricks was installed to allow the entry of air to encourage the fire and create a draught.
These changes, combined with the pine firewood used, ensured that the kiln performed very efficiently. It was so efficient in fact that very early in the piece it had to be restrained by closing the firebox air vents as the temperature began to rise too rapidly.
One the aims of the firing was to try to achieve an even temperature of 1300°C throughout the kiln, something that eluded us in the previous two firings. In those firings pots at the back were under fired with little ash deposited. The modifications to the “sutema” wall and the new firebox addressed these problems.
The chimney’s side dampers were used a little. Vertical dampers at the top of the flue used in the previous firings were removed. Two of the 4 side stoking ports were sealed. Of those retained the left rear one was used for stoking and the other (right front) was used for observing cones.
As feeding the beast can be an exhausting process the initial 8 hour shifts were reduced to 6 hours in the later stages.
The conclusions drawn about factors contributing to the kiln’s efficient performance:
- The type and condition of the firewood.
- The modified “sutema” wall.
- The stoking regime.
- The new firebox.
A noteworthy feature of the firing was fuel economy. Substantially less wood was used than in each of the previous two firings.
Compared with previous firings the stacking of the kiln tended to be open rather than tight.
The duration of the firing was 81¾ hours with the elusive 1300°C being attained throughout the kiln.
Some 28 people contributed pots.
The firing produced some outstanding results compared with previous firings.
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4
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14 - 18
May
2008
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Andy Hope
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Firing Duration: 102 hours.
Excellent weather.
Glaze tests prepared based on recipes in an excellent book “Japanese Wood-fired Ceramics” by Masakazu Kusakabe and Marc Lancet, recommended by Bruce Martin.
Number of people involved:
Loading 5
Shift leaders 8
Shift members 14
29 people contributed pots: most were satisfied with results – some were elated. The firing produced marginally better results than previous firing. Build up of ash was not as great as we’d hoped.
A crack developed in roof of front section of kiln from which flames issued forth. The front of the kiln acquired slight lean.
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5
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8 -12
May
2009
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Mal Sole
(Ebullient potter.
NZSP regional representative.
Former RAF pilot.
Air traffic controller.)
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The crack was repaired by replacing 10 bricks and the wicket door arch was gently nudged back into a more upright stance. The new firebox, first installed for the 3rd firing, probably contributed to these structural problems.
Firing duration: 101 hours.
Wood used: 12 cords or 43 cubic metres.
A minor earthquake after the kiln had been sealed prior to firing prompted some concerns that unintended tumble stacking might have occurred. These concerns were not strong enough to warrant opening the kiln. When opened after the firing it was found there were a few “kisses” where pots had fallen against each other and stuck.
45 people contributed approximately 700 pots (the most ever). Nearly all turned out well and many turned out spectacularly.
Ranae Palatchie, writing about the firing in the Wellington Potters Association’s newsletter, recalls discussing her pieces with Shige Ohashi. In reflecting on the results of the 5th anagama firing he observed “We must learn to expect the unexpected”.
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-Firing_Master_5th_Firing.jpg) |
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Menacing_Mal(Sole) - Firing Master 5th Firing
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“Formal” debriefings to glean and record as much information as possible, attended by shift leaders and others, followed the first three firings. The knowledge gained was applied in subsequent firings.
Apart from routine maintenance such as slapping adobe on the kiln (we have ready access to cow manure, part of our adobe recipe) and cleaning kiln shelves, the only major maintenance job was repairing the crack in the roof at the front of the kin and correcting the lean in the wicket arch.
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Shige Ohashi - Repairing the Kiln
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A cadre of experienced shift leaders and helpers has developed which has contributed to the confidence of all those involved in the firings themselves and in the necessary prerequisite – loading. Troublesome things like errant pyrometers no longer tend to throw people. There is now much more reliance on simply looking at and listened to the kiln as it goes about its business.
While socialising is an important part of the firings themselves, the undoubted social highlight of each firing is the barbeque that accompanies the opening of the kiln and the removal of the pots. The pots are laid out in the order in which they were in the kiln and photographed for future reference. Such has been the enthusiasm of those present at the openings that we have adopted the practice of erecting “crowd control” barriers around the kiln and designating who will be involved in the process of removing pots from the kiln and displaying them.
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Shige Ohashi - Weight Testing Kiln repairs
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It had originally been hoped that we would have at least two firings each year. However, apart from the two firings in 2006 we now aim to have one a year. This reflects the not inconsiderable amount of work involved in preparing the firewood, kiln maintenance and administration (advertising the firings, recruiting volunteers for various tasks, arranging rosters, receiving pots, etc). Of these tasks probably the most important is preparing firewood, without which everything else would be academic. We are extremely fortunate in having sources of wood, secured by Graeme Houston, and a small merry band of brothers who engage in the time consuming process of cutting, transporting, splitting and stacking the firewood. The actual loading and the firing of the kiln also requires the commitment of a large number of people. If these tasks become a chore then enthusiasm will wane.
The final word can go to Vivian Rodriquez (who describes herself as a “new anagama addict”) who, writing on the eve of the opening of the kiln after the 5th firing, wrote “I have heard people referring to the anagama as ‘the beast’ or ‘the monster’. I want to think of it as a gorgeous and lovely fat lady with an insatiable appetite for wood. On Saturday (the day of the opening) she will open her golden womb to deliver her creation. We will say our goodbyes before letting her rest until the next time”.
Alan Ross
1 December 2009
| Check out the results of this firing in the Events section |
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