‘Anagamania’ -1- 穴窯築き : Anagama Project 2011

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I will return and resume my latest Anagama building in the wood near Tring (Hertfordshire U.K.) as soon as I feel spring in the air. And now I have a good Trans-Atlantic companion. Trevor Youngberg who works in Woodbridge (Connecticut U.S.A.) will be building his Anagama this spring and hoping to finish by early June. He may have many questions about Anagama building and already started asking me some. I also receive e-mails with questions from potters and wood-fire enthusiasts, and I am getting too many similar questions to reply individually. Therefore, Trevor and I have decided to exchange our thoughts on my blog. I hope that we can encourage each other with our Anagama project and help individual wood-fire potters who are thinking about building their own.

From now on, information for most Anagama building (hopefully with a lot of images) and Q&As will be uploaded under the category ‘Anagamania’.

窯築きに関する問い合わせが頻繁になり、各人に返事を差し上げる事が難しくなってきたので、今後この手の話題はブログで扱うことにしました。何卒、宜しくお願いします

About Gas

Hi, I am a wood-fire potter, living and working in the Japanese tradition in Tring, Hertfordshire (UK). Following mediaeval potter's wisdom, I design and build simple wood-fired kilns called 'anagama' for long period of firing and 'raku-gama' for quick (glazed tea bowl) firing. My anagama firing usually takes 9 - 10 days.
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5 Responses to ‘Anagamania’ -1- 穴窯築き : Anagama Project 2011

  1. James Hazlewood says:

    Hi Gas,

    I hope you are well and that 2011 has been good to you so far. Samantha and I are well.
    Sorry I’ve not been in touch yet reguarding coming to see you again. I will be in touch soon. Would you still be interested in going to see the Aylesbury collection – not that I will be organised enough to sort that out.
    I haven’t checked back here for a while and only just saw your post with your teabowls – all of them are very nice indeed.

    I will be in touch soon.

    Kind Regards

    James

  2. Hello Gas,
    As you know, I look forward to beginning the process of constructing my second anagama this Spring. The goal is to finish for a summer firing. I’m generally horrible at estimating the time a project will actually take, but am looking forward to the process. My first anagama was around 30 cubic feet of stacking space and was fired 8 times over the course of two years. From those firings, I learned a ton and hope to continue on the path of discovery in a larger kiln…somewhere around 90 cubic feet. For the past year and a half or so, I have been working on the construction of a passive solar, post and beam workshop. A structure I designed and built to include a lean-to on the back side that will house the new kiln. Which brings me to a couple questions I have regarding kiln building techniques.
    From viewing your website I noticed that you use bamboo as framing for your kiln body. In the past, I’ve always used cut plywood and lath for forms. Because I am curious about the affect of uneven interior kiln walls on the firing atmosphere, I am wondering if the use of green tree branches may be a reasonable alternative to bamboo. My theory is that by creating a somewhat uneven basic form with the branches, I could then position bricks over the form in such a way that the corners of the bricks protrude toward the interior an inch or two…creating a jagged kiln wall. Do you think this idea may create increased turbulence and microclimates of varying reduction?

    Another aspect of the process has more to do with actual firing technique. In firing my first anagama, I discovered that the kiln can be “stalled” at peak temperature and held there for long periods of time, using small amounts of wood, by way of controlling the primary air and passive damper. When stalling the kiln, the primary and secondary air are shut down nearly entirely. Then to slow the kiln’s draw, the passive damper’s are opened entirely. After a time of stalled firing, the kiln is plugged, active damper is shut and the chamber is allowed to reduction cool. I’ve noticed that crystal formations in the ash glazes are, in my opinion, spectacular. I’m completely addicted to this style of firing and want to continue to discover and understand the results of my actions. My question is, because I’m considering constructing the kiln walls with hard brick rather than insulating ‘Castable’ (like in my previous kiln), is it possible that I will lose a degree of control over the temperature and atmosphere?

    I’m sure I will have more questions as the construction phase draws near and I appreciate your consideration as I mentally prepare for the next adventure! Best, Trevor

    • Gas says:

      Hello Trevor,
      I was very fortunate to learn anagama building skills directly from Master kiln builder, Furutani Michio.
      I used split bamboo and lath for my very first Anagama ‘Moby Dick’. I could not find good green bamboo in the U.K. and I had to ask my uncle (who had a big bamboo forest at the back of his house) to send it from Japan. Shipping cost me a lot, despite bamboo was free. I didn’t burn the bamboo frames after the kiln was completed. I knew bamboo would produce massive oily soot which could stick on the wall. Instead I went into the kiln and took all the frames down then built an inner wall with flues. I don’t burn flame-work because most of frames were green branches or bamboo. I mainly use bamboo, willow and hazel for forming kiln arches. It all depends on what is available locally and cheaply each time. Bamboo remains still my favourite material.
      I can not give you a clear answer for jagged walls because I have never built jagged walls for my kilns and I don’t think I will ever try jagged walls in future. It seems everyone likes the idea of jagged walls. I believe that jagged walls may create tiny turbulence in many places inside the kiln but will not have a major effect. This is my personal opinion and no-one has to agree with me. You should try your theory by yourself. I prefer rather old-fashioned mediaeval Anagama on a slope with ‘bun-en-chyu’ (literary means flame dividing pillar). I always had a big turbulence with these old ideas. I will upload some images of kilns with my next post for Anagamania.

      Every wood-firing has a stalling period at some point. You can not avoid it. I know it is difficult to control a small kiln like your ‘Hawkagama’. with controlling (adjusting) devices. My best friend, Svend Bayer is a very good potter and his firing usually takes 4 days while mine takes 8-10 days. It all depends on the kiln design and the length of firing. Trying to get temperature up by adjusting passive dampers may work well. Mind you, almost all my kilns didn’t have side-stoking holes, ash-pit, dampers and pyrometers. I don’t control my Anagama by force and devices. I have my own firing method but it is not suited for everyone. We talk about wood-firing techniques after we complete our kilns. Let’s build our Anagama first!
      Gas

  3. Hi Gas,
    Thanks much for your advice. I decided against the jagged walls and tree branches for the construction of the kiln. I felt it could possibly weaken the structure, complicate the building process and your words of wisdom, of course, were taken into serious consideration. In thinking about the turbulence caused by jagged walls, it occurred to me that the pots themselves most likely provide the bulk of the turbulence. Now, with kiln built, I am beginning to consider stacking techniques, wood selection and the coordination of a firing team. Luckily, two of my former students are on for the maiden voyage. We plan to give the new kiln, the “Piranhagama”, a first fire in mid-August. We spent last week making a group of pots that will hopefully fill the kiln. The design turned out to yield a 120 cubic foot stacking chamber. There is a step-down firebox and a side entry…that’ll be much appreciated. I’ll for sure share the results with you.

    I do, however, have some concerns about the design. For one, the chamber diminishes about a foot above the exit flue. I chose to run the cieling higher up in order to allow for more stacking space towards the tail. I justified this decision by comparing the back wall to a sutema….so am hoping the draw will be strong. Also, the firebox is about four feet square…about a quarter of the kiln floor’s length and floor area. I’ve noticed that some potters design in a firebox that is 30 percent of the floor area…not sure if this may have been a mistake…just wanted to allow for more stacking. Another concern is the insulative castable on the exterior. The kiln is built using Clipper firebricks…the castable backing is between 4 and 6 inches skinning the kiln. Over that, I installed a layer of stone….to counteract thermal expansion. I guess if the stones really heat up…I’ll have my answer. Anyhow, I’m enjoying the sense of experimentation and discovery that has been a part of the construction process and will emerge from the first firing. Preparing for the worst and hoping for the best. There’s always a solution to problems…nothing a little elbow grease and a positive attitude can’t conquer. Thank you for providing this forum for questioning, sharing and learning Gas. My Best, Trev

  4. Hello again Gas,
    We’ve successfully fired the “Piranhagama” for the first time. By successfully, I mean the kiln hit temp in a reasonable amount of time using less than the wood we prepared for the firing. (46 hours of stoking and about 4 chords of wood) In reflecting upon some of your nuggets of insight, I decided to fire the kiln by making adjustments to the draw almost exclusively by controlling the draft from the front of the kiln. By almost exclusively, I mean that for the first 8 hours of the firing the active damper/ flue shut off shelves were partially closed…this was done with the intention of containing the heat in the chamber as a smallish fire was tended while contained in the ember pit. In all previous wood firings, I’ve fired bisque ware exclusively…and fired fairly rapidly from the get go. Once we were up to around 425C…the fire was transitioned up to the firebox proper. At that point, the active dampers were opened entirely. No more adjustments on the back end from that point on.
    In firing a larger kiln than ever (for me), I noticed a few things that were unexpected…for one, the heat core of the firebox radiated a ton more heat! Thicker and heavier stoke doors will be the first improvement in preparation for the next firing. Additionally, the shrinkage of the castable insulation will be infilled with a high temp castable.
    Regarding the kilns ability to attain temperature, the draw was good, the heat migrated to the tail…cone 13 dropped completely in both front and back. My concerns about the finished quality of the work have more to do with the atmosphere achieved during the firing and at the point of closure. In past firings, I’ve used a large amount of green hardwood…here in Connecticut, black locust, red oak and hickory have worked well. Color wood is a common technique employed by potters…but I have only my own direct experience to draw upon. In the past, good flashing effects have been attained through what I figured was mostly due to the use of large amounts of green firewood. In this most recent firing, most of the material was aged and quite dry. My hope is that there will be active flashing that was encouraged by the close down procedure…another common technique that involves allowing the last stoke to burn down to the point of a plateau in in temp gain…around 1270C…followed by an abrupt close down of all air ports, spy holes, blow hole and active dampers. The ensuing flame show was a spectacular ending to a firing that proceeded with a vigorous tempo that was delightful (and mentally/physically taxing) for all of the participants. I’ve developed an understanding of firings that seems to support the idea that the fired quality of the pots reflect the spirit of the firing. I’ll for sure share a few pics of results…we plan to unload on Wednesday of this week. Thank you for your thoughtful advice and consturctive criticism regarding kiln building and firing techniques. Take care Gas, Trevor

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