Welcome to the historical section.
The following accounts detail the building and firing of the ASP Anagama kiln from 2003 to 2006

Construction of the new ASP Anagama kiln.

The ASP had its first Anagama kiln built by Torbjorn Kvasbo in 1998 as part of a workshop that was a spin-off from the Fletcher Challenge Ceramics Award. This was designed as a simple sloping tunnel kiln and was only fired to high earthenware temperatures. The kiln was rebuilt in 1999, to the same plan, but with double brick walls and more insulating adobe. In this form the kiln was fired on a yearly basis by a keen group of wood firers for up to three days per firing. Results were mixed to say the least, often not reaching cone 11, variable temperatures and effects all led to a withering of the initial enthusiasm of the group.

Personally I had some great pots out of the kiln, the majority coming from the last firing that I did in October 2002. However I had a lot more disasters, so a new kiln seemed the logical the way to go. I decided on the design through a process of reading about as many other kilns as I could and by reflecting on what worked best in the various wood kilns that I've built or used.

The ASP is beautifully set up for members who are keen on building and firing kilns. It is a membership based society and is there to help members with anything ceramic. So I knew I could build a new kiln and that I would get help from various members of the ASP. Also there were bricks available (from the old kiln and other miscellaneous bricks), space and it would add to the already extensive facilities the ASP has.
So a hardy group of members started in mid January 2003 to dismember the old kiln and build a new one. Every Friday and Saturday for four months a varying group, sometimes only two, sometimes half a dozen folks would turn up and learn about the intricacies of bricks. How to lay them, how to clean and grade them, kiln theory, etc...

The diagrams illustrate the basics of the kiln, but not all details are there. The basic thinking behind the shape was of jagged curves. Overall the kiln is tear drop shaped, with the widest point being where the first bung of shelves is set. Maximum pots near maximum fire. The stepping of the floor helps move the fire in a turbulent way towards the rear of the kiln, allows easy stacking of the pots and provides obvious points to side stoke. The roof is a series of curved sections, each independent of the others and up to two bricks wide. This stepping of the roof was to create turbulence, preventing an easy path to the chimney for the flame. The firebox was provided with a grate and was capacious for heaps of wood (and injudicious stoking!). The back bag wall was designed to restrict the draft and cause the flame to slow down. We had a passive damper and sliding damper system. The middle section we tried to tumble stack as much as possible, the back section was for more glazed work (like shino ware) and the front had a mixture of everything.

We fired for the first time in mid May 2002 even though the kiln wasn't finished as it only lacked the final thick coat of adobe. I wanted to see how it worked, and to modify it if necessary. This decision was the right one it turns out, as after the firing, as the kiln cooled and contracted, the brick arches flattened and a couple of bricks fell out. So we reinforced the kiln with more steel work. Also the chimney needed tapering, more brick height and a better sliding damper.

	Click on the image to download a larger pdf of the kiln design.

The first ASP Anagama firing in the new kiln, May 2003

It all started quite quietly, after last minute tidying up and finishing off the wicket, fire was lit in the central ember bed. Over the next three hours on a beautiful Friday morning the fire slowly grew, first spreading to the other ember beds, then up onto the grate of the firebox proper. The first shift is always a balancing act, trying to grow the fire in a slow controlled manner. Luckily all the pots were bisque fired and so the risk was greatly reduced.

Latter on in the afternoon the fire got hold and the kiln seemed an insatiable beast, temperature rise was easy and smoke really started to stream from the chimney. As the kiln heated up steam from the wet bricks and adobe slowly migrated to the outside air, forming a misty veil.

During the first night we let go any pretence of a managed fire and let rip. We needed reduction, so at about 950 degrees we had 4 foot of flame out the chimney and a slowing down of temperature rise. During the very early hours of Saturday morning the stokers energy was at its lowest and the kiln was still hovering around the thousand mark, refusing all attempts at getting hotter. But now, due to a very large build up of embers in the firebox, we had truly spectacular chimney flame, at least 6 to 8 foot of flame and the steel pipe glowed cherry from top to bottom. This also lead to a peculiar phenomenon inside the kiln where carbon built up into a thick cobweb covering all the pots and hanging off the shelves, very spooky. A change in stoking patterns bought about a drop in the embers and a rise in the temperature. All in time for a glorious Saturday sunrise.

The rest of the morning was devoted to temperature climbing and smokeless reduction, the cobwebs burnt off and by the afternoon we were ready for side stoking to begin. We abandoned the pyrometre when cone 8 bent but the dial read 1000 degrees. Come Saturday night and again we let rip, producing a spectacular afterburner effect in the chimney on occasions, but also a good rise in temperature.

Sunday dawned and we realised that our wood supply was seriously depleted, we'd just make it past the 2 day benchmark. So we stoked to the best of our abilities to get the last cones bending, 11 was flat at the front and half over everywhere else. At 2 o'clock it all ended in the last puff of smoke, the kiln was clammed and left to cool. Looking back it was an exhausting firing, the kiln took longer than I expected to dry out (stalling for eight hours at 1000 degrees) but it was an easy beast to stoke and control.

The results were revealed on the following Wednesday, cracked open despite the unloading being performed in a sauna atmosphere. The pots emerged to gasps or groans, mostly smiling faces and no major disasters, although the roof will need some attention before the next firing in August. All in all a very rewarding firing experience, especially for the team of hardy kiln builders who finally got to fire the fruit of their labours.

The 2nd firing of the ASP Anagama kiln, December 2003

After the first firing of the ASP kiln a number of concerns arose. Chief amongst these was the flattening of the arch making it unsafe to fire the kiln again. We installed a metal cage around the kiln and this added buttressing stabilised the arch and provided roof supports. Each section of the arch was also popped and the centre 20 bricks relayed. This also allowed us to replace some unsatisfactory refractories that we had used. It can be a gamble using a mish mash of donated or second hand materials, in this case it was some high silica bricks masquerading as normal firebricks, but which spall badly under uneven heating. Luckily we had also just been donated some genuine high Alumina bricks which fitted perfectly.

The chimney also came in for some attention as the metal tube proved unsatisfactory and a better damper system was needed. So we replaced three quarters of the chimney, installing a double sliding damper and completing the chimney with fire bricks, corbelling in to reduce the size and create a better draw. Other very useful improvement were cast side stoke ports and plugs and a fancy counterweighted main stoke door, a first for the ASP.

The second firing took place in mid December and many of the original group again took part. The kiln was loaded with bisqued pots ranging from domestic ware to sculpture. In known quite areas a little ash was sprinkled on the pots to help enliven their surfaces.

The firing commenced on Friday morning at 9.30am and followed the usual pattern of starting the fire in the ember beds and slowly building up the heat. The kiln was much drier this time and so heated up more evenly. Once it got dark we let rip with reduction and seriously stoked the kiln. The new chimney allowed much better control over the kiln and so when Saturday dawned and the cricket wickets next door filled with children dressed in whites we were not too smokey.

On Saturday night we again plunged the kiln into heavy reduction and tried to build up ember levels to cascade over the pots. Whilst doing this we also managed, once again, to generate carbon cobwebs dangling off all the pots and shelves. We also experimented with stoking patterns to find out how to build up embers and burn them away. We flattened all the cone elevens by mid afternoon on Sunday and soaked the kiln until 8.30pm. The final act was to stuff back into the firebox any embers previously removed and utterly seal the kiln.

On the following Saturday we cracked the kiln and removed the still warm pots. The results were very gratifying with most potters getting good pots out. An improved selection of form, clay and slips had widened the range of colours. We had the usual browns, but also reds, pinks, blues and greens. And the flashings left by the flame were good. We had blown in a small quantity of ash (about a 5 litre buckets worth) and that had helped create a more layered ash glaze. The kiln itself survived much better this time, with no movement in the arches. More insulating adobe is needed but the kiln is ready for another firing.

The 3rd firing of the ASP Anagama kiln, June 2004

It was mainly interesting for the modifications that we made to the kiln. We tried an idea out about limiting the gas flow at the back of the kiln by filling in some of the spaces in the back bag wall. The theory was that the gaps were now equal to the area of the chimney, so the dampers would have a more immediate effect and that more flame was being bottled up inside the kiln (a result of slower flame movement would also be to help deposit more ash on the work). The numbers of pots proved to be worrying as when we started loading there weren't as many as hoped so we spaced them out more. But by the time we finished more than enough work materialised and the front was densely stacked. The fire was lit on Friday morning and if you have a look at the log you can get a pretty clear idea about how it progressed.
The unloading was very revealing - lack of temperature was the main culprit in why it wasn't a great firing. This we pinned down to the modifications at the back of the kiln. It reduced the draw all right, but also our ability to really give it a shove for the last few degrees. Also, firing in Auckland in winter, damp place that it is, probably affected how well the kiln drew and the water content of the wood.

The 4th firing of the ASP Anagama kiln, December 2004

This firing attracted about 18 members of the ASP to take part and as a result we had lots of pots and people for the stoking duties. It meant we could densely stack the whole kiln and see what effect that would make. The only modification made to the kiln was a return to the way the back bag wall was in firing number two. For the third firing we had partially blocked the top three holes of the back bag wall to see if that would slow the flame down and even up the build up of the ember beds during side stoking. But it slowed the kiln down too much, we only just got some of the cone tens down, so in this firing the holes were reopened.

This firing went like clockwork, we reached all the benchmarks ahead of the other firings, and in the end reached a higher temperature overall, cone 11 was flat everywhere. The pots looked the best yet, with beautiful flashings and colours. We also used a some different wood, towards the end of the firings we used some Pouriri and Macrocarpa, in addition we also blew in a little finely sieved ash to help with the colour development.

We also timed out perfectly with the wood, 60 hours firing and all the wood gone. The kiln worked a treat in gusty, cool conditions and everyone went away happy with both the experience of firing and their pots.

The 5th firing of the ASP Anagama kiln, July 2005

It was a good firing that produced some beautiful pots. This time around it favoured the white midrange clays like Nelson White, giving them pinks and ochres, whilst the heavy iron clays were more subtle in their effects. The crew of about 14 managed very well in loading a tight stack. The kiln performed much like firing 4, except it punished us for the damp wood we had to use. The Auckland winter decided to get very wet during the month of the firing. In fact the kiln was loaded in the rain and a moat formed around it. Luckily the rain held off during the firing, but by then everything was a bit damp! Cone 10 was flat everywhere and 11 half down most places. The one good thing to come from the rain was a rebuilt wood shed.

The 6th firing of the ASP Anagama kiln, February 2006

This firing was a complete contrast to the last one – no rain made a big difference to the ease of loading the kiln (no leaping the moat around the kiln), although the firing was delayed a couple of weeks due to a storm that did soak the wood. We panicked a bit with how many pots we could muster – but in the end we had a handful left over and about 300 inside the kiln. A good keen group of stokers soon filled the firing roster and at 8am on Friday morning (17th February 2006) the kiln was lit. The advantage of the new wood storage sheds was pretty obvious from the get go as the kiln was hungry for all the dry wood. Stoking at night was again the highlight as the stoking rhythm is increased and the flames start shooting out of the chimney and firebox door.

During daylight on Saturday we toned it down a bit but the kiln was still climbing in temperature and by midnight on Saturday we had melted cone 11 at the front and flattened cone 8 everywhere – if we continued for the next 20 hours like this the whole kiln would be reduced to slag. So we found the heaviest logs and stoked the kiln like crazy – and pushed in the dampers, everything possible to choke the kiln and drop the temperature a bit. The visiting German potter Wiebke was on duty during this phase and was most impressed when, after three hours of heavy stoking finished and we finally looked into the kiln, found a thick mat of carbon cobwebs obliterating all the pots in the front – so thick hanging off the arch they looked like incandescent Pohutukawa roots dripping down into the kiln.

Sunday dawned and again we toned the firing down and aimed to bring it back up to temperature to melt down all the embers we had built up. By 9pm Sunday night we had burnt all the wood that was for the Anagama firing and so closed the kiln down confident that at least we had managed to flatten ever cone 11 in the kiln.

This firing was the last one that we had stocks of lovely seasoned and dried mill slab – for now on we have to rely on cut up pallet timber and the problem of nails again. We ended up burning about 976 cubic feet of wood, or in metric 28 cubic metres, or about 7.5 cords a lot of wood whichever way you look at it.

The kiln was drawn on Saturday midday and as the pots emerged we realised that we had fired the best load yet. The clay choice and type of work was starting to all click with the kiln. Some pots had the most intense reds and oranges – more common coming from the soda kin than the Anagama. Lovely drippy ash glazed pots were well treated by the side stoking efforts. Nothing had moved to dangerously and everyone can be proud of his or her efforts.

The 7th firing of the ASP Anagama kiln, February 2007

This firing of the ASP Anagama kiln was a real learning curve for Jo-Anne Raill. Faced with my imminent departure someone else needed to learn the ropes of how these firings are organised. Although they appear casually run, behind the scenes a lot of planning and preparation has gone in. The wood chopping alone takes weeks of co-ordinated effort and then there is the issue of pots, stackers, stokers, food, rosters and collecting money. All jobs which Jo-Anne became very familiar with, including stepping up when holes appeared in the stoking shifts and managing to nearly stay awake during the whole 60 hours of firing.

After all the drama of the firing the unveiling all went according to plan on Saturday and revealed a kiln load of brown pots, luckily that’s exactly what we wanted. These events are a huge amount of fun to take part in and the more you lend a hand the more you get out of them.