Over the last couple months, things have changed. A smaller kiln is in the works. Smaller everything...amounts of wood, firing time, firing crew, prep time in general. Quick turnaround....versatility will be a bonus! Fortunately, my friend and fellow potter, Stephen Rodriguez, has accrued a hefty stock of both soft and hard bricks over his thirty years or so of gas kiln building experience. Between his bricks and fellow potter, Louise Harter's 1000+ Empires, a small kiln may be ready to fire in the next 4-6 weeks. We've nearly completed the base layer of the kiln.
To begin with, the pad was excavated to level, layered with 3/4" gravel and a cinder block base was laid dry....two high/18'. Then we layered the top of the cinder block base with 1/2" cement board. Building a 2x4" frame, we cast the slab using a mixture of cement, 1/2" gravel, plenty of perlite and sand. A pure concrete slab 3:2:1 Gravel/Sand/Cement was cast for the chimney base slab. The firebox floor was cast in a heavier perlite ratio than the chamber slab.
We then cut and fit high alumina 5/4" shelves for the floor of the firebox and layered the chamber floor with 12x18" soft brick lintels. For the firebox arch, Stephen free-styled a sprung arch curve, I traced and created a form using plywood and a jigsaw. We cast the firebox grates with Mizzou castale and are now in the process of, having placed hard brick lintels around the permanent shelf posts, cutting and fitting hard bricks around the newly places hard brick 12x18" lintels.
The form for the kiln chamber is a graduated 1:1 catenary arch. The interior opens up to the center section and tapers to the tail...a 1:1 ratio is maintained throughout the chamber. It was made from plywood cut to a gravity-formed archs and bound by 1/4"x10' strips of Ash.
The chimney will be 36x36" on the exterior to 6' height and corbel to a 14" square opening to 13'.
The firebox is roughly 1/3 or the chamber floor area. Stacking depth is 6.5' with an average height/width of 42". Stackig space will be approximately 60c.f..
There's a lot of work left yet but we've taken care to make a solid base for the kiln. The firebox has 3-3x36' grate slits and they are divided by the 9" depth of the castable grate.
Hoping to fire in the next couple months..this summer for sure ;)
A 1:1 catenary arch has the equivalent of exactly 2/3 the area of a 1:1 square of the same dimension.
42" average height and width equals 1764square inches/inch.
1 cubic foot =1728
21,168/1728=12.25 cubic feet of stacking per foot.
6.5' chamber length x 12.25 cubic feet stacking per foot of chamber=79.625
At least 60 cubic feet of stacking will be available.
7 chordsThe winter firing was a step into a new realm. The elusive chocolate flashing emerged as a predominant kiln effect this time around. Copper fuming was a complete surprise and a new direction of exploration for sure. A large Oribe green glaze...stacked up high in the front of the chamber provided volatilized copper to a number of pieces to the rear...gold and copper sheens developed on the raw surfaces of porcelaneous stonewares and porcelains. the changes made this time around include:
Stacking the front two rows with extra room above the pots...shelves in line re: stack height...allows better combustion and ash migration to the center/rear.
We fired with green wood included in each stoke all the way up to the last couple hours of the firing.
We used large split chord wood 5-7" split diameter. 2-3 heaping wheel barrows per stoke...every 20-30 minutes.
Louise ran the overnight before the final day and stoked lightly with dry thinner wood to get cone 10 to start going over...this was a good prelude to a intense finish.
We loosened up the back a bit...still a little tight...but the back pressure throughout the firing created a beautiful color palette.
The long and extreme stoke cycles were key here...so much depth in the surfaces...the green wood really brightened the colors throughout the kiln.
Although there a number of dry pots around the tail...the kiln effects by far outweighed the losses...metallic asteroid blues with crystals and fumed glosses...oranges to chocolates...I'm so thankful and humbled by the beauty that can be attained through this process. Cannot wait to fire again in June.
This firing was kinda slipped in as we had the majority of the wood split and there was half a kiln worth of pottery bisqued and ready...we had an over abundance of pieces that I held on to, from June, for the following firing.
Aside from the aforementioned changes, the firebox was modified...no pieces on the floor except to the very back wall.
Shut down procedure...approaching the finale'...I shut down the air in front and fed small sticks in to raise the temp( at center) to 2250...shut down included 3-4 full wheel barrows.. enough to fill the firebox to the top...the stoke door was blocked with wood. Exit flue dampers were then closed and all air inlets were stuffed with kaowool. Green was mixed in to the final stoke.
7 chords total, mixed hard wood and 1.5 of green oak.
This process never stops teaching and rewarding ;)
This June's firing was a mixed bag to the extreme!
Large pieces along the top of the kiln were covered in ash and responded beautifully....Mackenzie Shino with Redart, Raw Hawthorn Fireclay body and Blue Oribe thrived in the kiln's environment.
The tail was stacked a bit too tightly this time around...I have a clear idea of the results as they relate to temperature and surface effects....cannot wait for the next one which will be sooner than later.
We've been on a once a year firing schedule the last three firings and feeling the need to ramp up timing with next one...there's plenty of unfired student, fellow potter and personal work...enough the fill the kiln again and more....plus, we have the wood split and cured.
Thinking of simplifying the firing process this time around...I've invited various artists to participate and take ownership in different aspects of the process and I'm sensing that it's time to re-engage with the oversight and direction of namely the tail stack and final shift. I've been inviting folks from the surrounding community and region to participate in the firing activities with the intention of connecting with both the established surrounding clay community and local residents that are completely new to the process.
The community building aspect is important to me....the most important aspect...I believe that the quality of the work reflects the approach to the process and by incorporating others...new information and insight is gained...furthering the end quality of the work.
Next firing: skeleton crew and very small social gathering for the finnale'. Back to basics ;)
This summer's firing was what I view to be our best firing ever. I say this because the overall quality of the pieces was so varied and beautiful. The success rate was in the high 90's and I couldn't be happier with the level of quality. The results reflect the effort we've put in as a team of wood-fire potters. The crew is evolving to comprise more professional potters than former students...a progression I hadn't anticipated but welcome. Former students are absolutely still a factor...just nice to be working with potters that are fully committed to the craft.
The difference this time around had a lot to do with the stack. More pieces than ever before were packed into the kiln. We've added a second firebox to one side at the center of the chamber...it's 2' deep and 18x18" high and wide. Because we packed the kiln super tight...the secondary firebox aka the Nos....didn't have the jet fuel effect this time around regarding temp gain but the flashing to the back side was amazing. Blown away by the effects of wood and atmosphere. We're in a new chapter and could not be more thankful for the people that contribute! Next time around, more porcelain and bigger pieces.. Looking forward to the next big fire summer 2019.
I'm thinking this is our best firing yet. Had a lot to do with the preparedness and crew for sure. A good group of folks stoking and ample wood split, seasoned and stacked for efficient working. A big change in the stack involved a secondary firebox in the bottom center on one side. This was huge in that the flames were given a chance to completely combust...nice glaze melt and ash deposits toward the tail. This firing yeilded great results that are featured on the summer 2016 unload page.
The December firing was a good one. 3 days total.
We fired through five chords of mixed wood; pine, mulberry, black locust, maple and honey locust. We saved a stock pile of honey locust for the finish. Turns out that we fire with a different mix of woods each firing; and each wood has particular burn characteristics. It does make things a bit tricky...especially when a new wood is introduced. We had never fired with honey locust before; but I had noticed that its heat index is very high and we were thrilled to have a good bit of it (1.5 chords) to bring the kiln chamber to it's max temp. What happened baffled us for a bit. There was low pressure over the kiln for the last day and the honey locust embers built up both in the firebox and below the firebox something fierce. We tried to increase the draft by plugging passive dampers in the flue, opened up the ember box to max air, altered stoke patterns...nothing would get temp to the back of the kiln. Would have been nice to have a chord of thin-split pine for that! Next time for sure and from now on. The front and middle hit cone 10 plus and the few pieces we've pulled already show spectacular results. At the end, the near white heat indicated plenty of temp. There may be a few re-fires this time but from what we can see so far, the atmosphere of super heavy reduction was good for shino crystalization and flashing...we've seen some beautiful chocolate flashing on several different clay bodies. Can't wait to get at the rest!
Stephen Rodriguez shared a couple new glaze recipes with me for this firing and I'll post them once we've seen the overall results.
Will continue this post after the unload.
This firing was special in many ways. First of all, a great friend of mine, Michael Strand, came out to participate in the event. His presence was awesome as he has fired anagama kilns all over the world and is a world-class teacher, potter and activist.
Several other potters visited the firing as well...Stephen Rodriques of New Haven, CT. Mark Potter and Louise Harder and Kristen Muller also partook in the festivities.
For me, the best part of visiting potters was the exchange of ideas and forging of friendships. I learned more this past firing than ever before...or so it seems. Mostly, the feeling of being a part of an inclusive group of clay enthusiasts was thrilling to me.
Former students took a larger role in the firing of the kiln. Michael suggested I give even more responsibility to these folks as they have proven their commitment to the process. That'd be great, especially since my two little ones are requiring ever more parental focus as time wears on.
Regarding the firing itself, we packed it fuller than ever. The results were stunning in most of the kiln. Although the tail was packed a bit tight and we had trouble reaching max temp in that section. Always lessons to be learned...but some spectacular results.
Next time, will fire a bit faster...3.5 days for this one...next fire, Dec. 2015, will be 2.5 days with a high temp hold for 24 hours.
Will stack looser throughout and create some open channels for flame and some tightly stacked sections to create micro-climates. There'll be a larger percentage of 25 lb. plus pieces in the kiln too..looking forward to seeing broader surfaces and their variations.
The firing is slated to finish up New Year's Eve...so should be a fun finale'. Best, Trev
For me, friendships, enthusiasm and team-work are at the core of the wood-firing experience. A deep level of trust and understanding has developed over the past few years as the core firing crew has congealed. We, the firing crew, find satisfaction in taking on responsibility and welcoming opportunities to creatively problem solve. Gradually, a new aspect of the firing process has emerged, one where sharing the responsibility of overseeing and executing crucial aspects of the firing has become the tone of the firing. A big part of the value in pottery involves the friendship and bonding that is woven into the fabric of the wood-firing experience.
The June firing was huge for me personally....the success rate and overall quality was beyond my wildest expectations...yet there is a sense that a continued commitment to the process will yield information, discoveries and goals beyond any of our preconceptions. Exhillirating stuff! Planning to fire again December 2014 ;)
The firing was a success! We fired for the better part of four days and were blessed with temperate weather. This time we burned through seven chords plus...due to the use of roughly half pine plus assorted hard woods. The kiln was packed fairly tightly...and we fired to a soft cone eleven. Knowing that wood ash generally melts at 2150F...explored a slightly lower temperature range. Towards the end of the firing, we stoked the better part of a half chord of black walnut. The results were interesting on one of the clay bodies, Lehman 12D. The colorations were nice in that the flame/ash side of the pieces formed a green ash and lignt clay background...the lee side of these pieces revealed the more interesting surfaces. A chocolate flashing color accompanied matte oranges and yellows that broke to white. A totally new color range and one the we found worthy of further exploration.
Trying a new porcelain mix from Amherst Potter's Supply, there were some nice flashings of oranges and some yellows...still think I prefer the Sheffield mix. Next firing, will try another 1000# batch of the 12D and another of a body that will be decided upon in the next couple weeks. Would like to mix up a couple new small batches, 150#, of test bodies.
This firing, the eighth with the Pyranhagam, was significant for me in that it marks a point at which I feel as though we, the firing crew and myself, have gotten to know the characteristics of the kiln...stoking and stacking techniques, zones, glazes that perform well etc. For me, it is a chance to step into a new realm of firing in that the more technical question and answer dialogue is becoming subtler. My hope is to scale back to firing on a six month schedule....or better yet, whenever the kiln is filled with pieces that we've crafted with care and not rushed in any way... and focus a bit more on studio work. There are pieces that take a bit more time to create...plus ideas that would be fun to expore that I have been holding off on due to the primary concern of firing the kiln in a way that yeilds consistent quality...a daunting task consdering all of the variables involved in anagama firing.
Another discovery this time around was the use of what seemed to be excessive sawdust in the wadding mix. The recipe is sawdust with as little fireclay as possible, just enough to bind the sawdust and then a couple scoops of alunima hydrate. (a discovery many other potters have found themselves) I know that is not an exact recipe...but the result was literally a crumbling of the wadding as it was removed from the pieces. If pressed, I would say the recipe would be three parts saw dust, one part fireclay and an eighth part alumina hydrate. Rather than making balls with the wadding, which was impossible, clumps of wadding were added to spots of glue. A noticably soft line of demarcation between clay and wadded areas was a nice improvement to wadding marks of the past.
Photos to follow.
So today is the start of the firing. The last few weeks have been busy with last minute series of pots, splitting, glazing and loading.
The kiln is packed relatively tight...we found that a tight stack and a 12 hour hold around 600F dispersed ash evenly throughout the kiln the last firing especially. Thinking the tighter front stack especially acts like a screen the draws and disperses ash throughout the chamber...a discovery based on previous firings in which we stacked looser in the front.
There are five rows deep of shelves in the kiln and the first two counting from the firebox are exclsively stoneware...have found the porcelain likes the center section best...flashing and fine ash build up.
Our plan is to fire the kiln at 180F for 12 hours then move to a 30F/hour rise to 600F...so around midnight we'll start the 30F/hour heat rise again. Our goal is to be at around 1500 by the 48th hour. At this point we will pay extra careful attention to the atmosphere so as to allow for full oxidation before re-stoking.
By hour 72, we hope to be around 2300F and work the kiln to peak temp. and hold till hour 84.
During the initial phase..up to 1500ish...the passive dampers will be pulled to the point the we get the minimum draft necessary to maintain heat climb. After this, we will increase draft only as required.
Adjustments in the firebox occur mainly when we achieve orange-heat...at this point we close off the lower/primary air arch...this serves to increase draft a bit, keeps embers from accumulating and shields the stokers from excessive heat radiation.
Once we have held at temperature for several hours...we will introduce a half chord of Black Locust to provide the heat and ash that should get us to a soft ^12.
Shut down will be as usual...a couple wheel barrows of wood in the firebox followed soon after by a complete shut down of all air ports, peep holes and active damper...this technique has proven inself to be good way to achieve reduction cooling and flashing at high heat.
Each firing is so fun and exciting...the information gathered each time never fails to inspire the next firing. By far, the most satisfying aspect of the firing is the shared experiences with the firing crew. Mostly former students comprise the crew...a good friend Jim is a major contributor to the process....making pots, loading firing and unloading/clean-up. Without these guys there's no way this event could take place...so thankful that we've all taken ownership in the process of firing the Pyranhagama...without this process...may not see these guys regularly...good in all ways!