Secondly, my chimney was also a bit short, so I gritted my teeth and bought another taller ladder, and enough bricks to add ten rows to the chimney. The expensive part was the ladder — $90. I also dropped my grate one brick level so that the firewood rests closer to the coals.

The upshot is that the kiln fires to cone 10 without having to resort to careful stoking of kindling at the end and it doesn’t smoke while being used in boury box mode. In order to melt cone 11 flat, I still have to stoke small sticks by watching the chimney till the flame disappears, then stoke a stick, watch the chimney flame till it disappears, stoke a stick, etc. etc. I don’t need to go that high, but I like to know I can. I think the extra high temperatures sometimes cause interesting cracking patterns on the surfaces of the pieces.

I still like want this kiln to perform somewhat like an anagama — just smaller with a shorter firing period. So periodically I open up the front inlets, brave the smoke, and beat and stir the coals vigorously. It seems to be working. For example, the piece below was glazed only on the inside. Despite the fact that the outer surface was completely raw, the fire exposed side developed almost the same glaze color as the white liner glaze except with the added bonus of areas of ash based olive green (bottom right photo shows the front side). I think with a little practice, I may be able to avoid glazing completely and just rely on the fire. Click thumbnails for the big picture.

Steve Harrison’s (link 2, link 3) Suggestions:

I think that the problem with the smoke coming out the lid is mostly to do with the short chimney, as you identified, but I also think that it is to do with the big air inlet/stoke holes at the bottom. Once I have enough ember to get the wood on the hobs to ignite, I close up the bottom hole completely and only have a smidgin of air going in under the embers through the mouse hole. This concentrates the draught in through the top holes and draws the smoke and flame down into the throat arch and chamber.

Claudia MacPhee’s Suggestions:

Thinking about how my little kiln fires makes me really wish I could go out and run a load through it now! Alas, too cold….Just let me know what parts you want to see and I will try and get some photos up on my blog.

I made the bourry box exactly like the one in the diagram in the book. Counted the brick and didn’t use any ‘innovation’. I put in the brick hobs and cut my wood exactly 26″ long. A bit of a pain, but works well.

Usually I start a small campfire in the bottom of the box about 9 pm. Two big pieces with a bunch of paper and small stuff between them. I feed it from the bottom until it is going good with a few coals, then pile on more whole logs through the top. Don’t get too excited about a huge fire at this point. Mostly just keep it going until there are lots of coals then heap if full of wood, close the damper and put the three bricks in the front.Primary and secondary air vent are closed all this time. It is usually around midnight and I go into the house for a nap. Set my alarm for 4 am., get up and make a pot of tea. Fill up my thermos and get a cup full and go to check the kiln. There will be some coals left and I unbrick, pull out the damper and stoke it up, again on the bottom. Just keep filling the box with all the junk wood I have collected from around the yard and odds and ends from bucking the slabs exact. About every ten minutes I throw more stuff in. At this point I use aspen (tons of ash), pine/white spruce and hunks of willow. Willow is the hardest wood I can get. It grows very slowly up here with lots of cold and little rainfall so is tight and heavy. The willow I use has been dead for many years and is bone dry. It makes a really good, long lasting coal bed.

After about fours hours there are enough coals to go to the hobs. This is one of the coolest parts of the firing. I will take an armload of slabs, three to four inches thick, open the top lid and quickly place them on the hobs-it is like magic! They burst into flames and are pulled down into the kiln! After this point I keep the hobs full. The point here is to never let a bunch of cold air flow between the pieces of wood. So as it burns up put more pieces on the opening holes. Hard to describe. I try to lay the slabs in with the cut side up. There are always at least two layers. Also start using the primary air. The bottom three bricks are put in and clammed up.

I take a clock and a book out for the firing. Put new wood on every 10 to 15 minutes. Fill her up, go off and feed the chickens, fill her up, go inside to get some food.

My first firing I grossly under estimated how much wood I’d need. By 6 pm I was using my time between loads to buck up more slabs. Had enough time to do an entire wheel barrow full between stokes. That never happened again! Also I have never used the pyrometer to fire. Every body gets so neurotic with those things. I try to take the “Laid back” part seriously. I live in a beautiful and quiet place. I sit there and listen to the birds, read my book, hear a boat out on the lake or a plane going by.

After I go to the hobs I’ll begin the side stoking. Now this is the pyro dream, a technique from the Aussies known as ‘flamethrower’. You pull the brick, place a handful of small, long wood in and just hang on to it for a bit. It blows up and the flame goes in huge circles.

So the rhythm is-fill hobs, pick up sticks, pull brick, put in wood, hang in there for a couple minutes, drop them in, replace brick, sit down, drink tea, read book or stare into space for ten minutes. I have mouse holes but have never used them. Also have never needed secondary air. Usually keep the primaries about half open, just enough air to keep it from ‘chugging’. My first firing I had cone 11 (highest one I had) melted. Got some awesome hare’s fur on some bowls near the front. Didn’t side stoke that one so the pots near the back when in for round two next time.

I am dedicating my life to melting as much of the Coast Range as possible…lots of goodies to melt in this part of the world, plus a nifty bunch of volcanic ash, local copper and glacial silt that makes wonderful glazes. Chinese stoneware glazes, especially the iron ones really do it for me, I love them lots. I put in lots of glazed pots, but want flashing on them rather than a ton of ash. By this time I know where to put pots for what I want the kiln to do to them. Believe me, you can get all the ash you want at the front end. This is getting much too long. If there are any more questions, just ask. I have found this a really fun kiln to fire, and can do it by myself. I have children your age, so if an old lady can do it, how hard can it be??

Good luck!

Claudia

Aside from the work, firing the anagama is expensive.  Just the wood itself is a significant expense.  For example, I’ll usually burn 2.5 – 3 cords of firewood (@ $200/cord) and two cords of millends (@ $125/cord), plus use about $75 worth of propane.  Then there are lost minerals — every firing uses a decent amount of fireclay and grog in wadding (I’m guessing about $20 for wadding).  Other consumables include welding gloves (I go through three pair per firing: another $40), I easily lose five firebricks per firing at $2.50 each (and I have to Canada to get them): another $12.50.  It seems I buy a kiln shelf every other firing at about $35 each, so $17.50 per firing in shelves.  Without much effort, we’re talking about a cost per firing of approximately $1000, not including clay to make the pieces or food to eat during the firing if, as with me, you don’t live where the kiln sits.

So while I love firing the anagama, I’ve been wanting a kiln that would allow me to wake up on a Saturday, decide on a whim to fire, and be doing it that evening.  My interest in a throat kiln which would allow me to do such firings began with my interview with Steve Harrison some years ago, and even more so after I received a copy of his book “Laid Back Woodfiring“. 

Building (only a sketch, more details in later posts)

I plan to post a more detailed description of the construction in the coming weeks.  For now, I will say this: I basically built the kiln from interview with Steve Harrison’s plans in Laid Back Woodfiring, although in a nod to Furutani, I built a tiny sort of sutema between the kiln body and the chimney.  I didn’t build in any mouseholes, and instead of connecting  lower legs of the angle-iron braces on the firebox corners near the kiln body by running the brace under the kiln, I simply connected them at the top and buttressed them at the bottom.  I also set up the front air vents in a manner that I’m more familiar with.  I did none of these things for technical reasons, and I am not in the least suggesting that my kiln is better than Harrison’s — I just did them because it was either easier and I’m sort of lazy, or because I wanted to continue working with systems I’m already somewhat familiar with because of the anagama.

OK, by now, you’re probably wondering what the kiln looks like. Here are a few pics:

preheating with propane (larger image)

firebox and kiln body (larger image)

glowing kiln (larger image)

firemouth (larger image)

chimney (larger image)

I had the lid seen in some of the pictures above fabricated from steel and I attached refractory fiber to the inside of the lid (nicore wire strung through porcelain buttons I once-fired in my raku kiln). I cut out spaces in the fiber for the primary air inlets, and riveted a piece of angle iron to the top of the lid to act as a ledge for soft insulating firebrick splits which I intended to use to control the primary air inlets.  During heat testing, I realized that fire seeps up through air inlets, travels along the metal under the insulating firebricks, and then escapes.  Because some parts of the lid are hot and others are not, the surface takes on the shape of the ocean in a hurricane.  To remedy this, I riveted another piece of angle iron to the lid an tested again — same result although more constrained in the affected area.

Worse than the seeping fire though, was the smoke.  Prodigious amounts of smoke exited through the primary air inlets and made it practically impossible to stand next to the kiln.  Seriously, to fire the kiln with those air “inlets”, or smoke outlets as I think of them, I’d need a fireman’s respirator.  It would have been worth trying to see if carving the bricks so that they filled in the air inlets but also had a ledge so that they could not fall into the firebox, would have worked better, but there was a major problem with this idea — I would need six bricks and I had only one, so a trip to Seattle (three to four hours round trip) would have been necessary.  Besides — if I did open them to allow air “in”, what exactly prevents tons of smoke from seeping out the top of the boury box?  Either I don’t have a good understanding of how the boury box design works — I never hear about them belching smoke like a coal fired steam engine — or people don’t talk about that.  The only thing I can think of that would make it work would be a chimney twice as tall or taller, but I don’t want to build a 20 ft chimney let alone buy any more bricks.  Besides, smoke rises and a hole right over the fire is going to let smoke out unless the chimney has enough draft to power a rocket, and I don’t want the flame to move through the kiln that fast.  Anyway, I didn’t want to suffer so I took some scrap fiber and sealed up the holes, figuring I’d just use the front air inlets as I do with the anagama.  Then I weighted the lid to give it a good seal and moved on.

Firing

Firing the kiln went very well.  I candled the kiln overnight through the front air inlets (secondary inlets in a proper boury box, now primary in mine with the lid vents sealed) with the same raku burner I use to warm up the anagama.  Over the course of three hours, I brought the burner to full power and added in a weed burner also gradually brought to full power.  At 11:30 am, I started throwing in charcoal while the gas burners ran, and in about an hour, emptied a 20 pound bag of charcoal into the firebox.  This gave me a nice coal bed, at which point I began stoking small sticks and adjusting the gas to keep my temperature rise steady with same method I use for the anagama as demonstrated here:

Once I hit about 20 mV in the front and 17 mV in the back (I could see the edges of bricks inside the kiln glow in the mid-teens), I attacked, stoking aggressively with wood chopped thinly enough to stoke through the front air inlets.  I would periodically hold my breath, and drop larger logs on the hobs through the top lid, letting those burn till they were coals and would crumble on the next stoke.  Two to three logs seemed like a good amount to stoke.  Prior to stoking the top, I’d crush down the coals on the floor into small pieces and push them into the kiln, hoping to get some koge effects on the front pieces.  After stoking the top, the temperature would rise, and when it began falling, I’d go back to stoking the front inlets.

This process worked very well, and with a little side stoking, the front and back temperatures were pretty even.  Eventually, cone 9 laid down and when cone 10 was bending, I called the firing.  This occurred around 50 – 52 mV (new thermocouples — they will get less sensitive as they get used more).

NOTE: pyrometers are voltmeters and pyrometers that will output to a computer via a serial port are expensive while voltmeters that will do the same are cheap. I am mostly interested in whether the temperature is rising or falling rather than a temperature readout, so I use voltmeters to monitor temperature. This is why all my references to temperature are in millivolts rather than degrees.

I capped the chimney (I made a slot in the chimney for a damper but have not cut a shelf to fit that yet, so I fired damperless like Furutani suggests for anagama kilns) sealed up the kiln with a good amount of coals on the floor and wood still in the burning phase on the hobs.  My thought was that the kiln would cool quickly and closing the kiln with remaining wood would slow that down.  My worry was that ashes would blow through and make dry gray sandpapery pottery.

The firing took about 11 hours.  I burned about a third of a cord of wood (mostly firewood, but a good armload of thin millend sticks I have) and used approximately five or six gallons of propane (I use two 40 pound tanks on the raku burner and one 30 on the weed burner — they were still very heavy after I was done).  I used a couple pounds each of grog and fireclay, and 1/4 package of coconut husk as combustible material in the wadding.  I could stoke the kiln with regular leather/canvas work gloves that cost $2/pair and ruined only one pair.  I doubt I spent more than $85 firing the kiln.

Results

I was fairly happy by the results.  The pieces I put in the kiln were a random assortment of rejects that have been sitting about the studio for a while made of various stonewares, porcelains, and recycle clays.  I received a bit of haikaburi glaze on the front guard piece that received the brunt of the coals I’d push into the kiln. I’m quite pleased with the warm blush on the stonewares but the porcelain is a bit too pasty-dumpling-white.  I didn’t quite get high enough in the back, or wasn’t high enough long enough there.  Feldspar granules in the recycle clay peaked out, but did not melt.  Also, I wouldn’t mind a bit more wood ash on the fronts of the pieces.  All that said, for a first firing in a new kiln, I feel it was a complete success.  For my next firing, I will sidestoke a bit more aggressively and add 50% to the amount of time spent firing with wood (measured from when the charcoal first hits firebox).  I think that will ensure I fire the back of the kiln to temperature, will deposit a little more ash, and might be enough time to let the feldspar melt.  I might also let the kiln get a little hotter — my silica sand didn’t melt at all and I’ve been having fun sprinkling that on pieces recently.

Here are some pieces fresh from the kiln. I’ll devote a post to pieces later.

cones 9, 10 & 11 (larger image)

fire blushed bowl (larger image)

thin liner glaze (larger image)

light ash glaze on front (larger image)

coals make haikaburi (larger image)

back underfired (larger image)

Here is an example from the sixth firing, one of the most beautiful firings and the most disastrous due to multi-level shelf collapsing.

  Full size image.

This piece was just back of the firebox — a band of black koge can be seen in the front of the image.  The rest of the images from the sixth firing are posted on this site, but the location is pretty buried — I should add them to the photogallery.

Anyway, Furutani’s kiln design has no trouble melting sand.  In fact, it is beginning to dawn on me that I will have to work harder to keep firing temperatures down a bit, as I believe I’ve been overfiring to some degree.

It was a very hot firing — cone 11 laid flat front to back (I don’t have any higher cones).  However, I think getting it so hot is detrimental in that the glaze tends to run completely off vertical pieces.  There are two problems with this — first, the glaze is gone, and second, foot grinding is a huge chore.  Perhaps in future firings I will work on controlling the maximum temperature to no more than cone 11.

What was most excellent however, is that I avoided the gray-gunk I mentioned previously by not overstoking.  I figure that when overstoking, I probably have a lot of gritty unburned wood particles flying through the kiln.  With optimal stoking, I still got blackening on the front sides, but the carbon creates an inky black glaze rather than 30 grit sandpaper.  I’m completely OK with inky black glaze — it looks neat.

  View full size.

I also finally managed to mimic the surface of the floor bricks on a piece, specifically, the blue marbled glaze that forms where the floor sand melts onto the bricks.  The sand itself is inexpensive white sand that I buy at Home Depot — last time it was around $5 for 100 pounds.  The result is beautiful and the piece below is one piece I feel completely happy about.  It makes me want to get a bright light and a magnifying glass and mentally tramp through the mountainous landscape.

First, inspirational bricks:

  View full size.

A snow capped mountain range:

   Photogallery on this piece.

I also experimented with some local clay I was given a while back by a friend doing some construction work around his house.  The clay he gave me is everywhere around here, except it’s usually 4-6 feet down so getting it is difficult.  It is a blue-gray color in its natural state.  When I made some test pieces with it (full report here), the 100% “dug-up” clay melted into a beautiful glaze.  For this firing, I decided to try lining some of my pots with this clay.  The results were interesting.

First, the failed cup:

  View full size.

Same clay used as a liner glaze:

   View more images here (pics 6-12) and here (pics 6-12).

Finally, I’m also very happy with my new kiln monitor setup.  I had been using the software that came with my Radio Shack Digital Mulitmeters.  It was lousy software.  Recently, QtDMM has been released for Linux and OS X.  I put together a system with an old Mini-ITX board powered by an aging VIA Nehemia 1ghz processor (think 5-6 years old).  I used Ubuntu 8.0.4 for the OS.

  View full size.

The added processing power over my old system (it died between the this firing and last year’s) allowed me to set up a chimney cam — basically just an old DV camcorder connected to a firewire port.  I used Kino to display the feed.  This helped save my knees.  What I used to do is go up the steps to the mid-level, and peek at the chimney tip through a gap in the roofs covering the kiln — when I saw the flames die out, I’d run down and stoke.  Well, my knees are getting beat up by running up and down the stairs during these firings.  Now I can just stand by the kiln and watch the chimney cam.

This is what I used to see:

  View full size.

This is what I see now:

View full size.

When all is said and done, I’m totally satisfied with this firing.

PS:  if you’ve made it all the way down to the end, enjoy a sunrise:

  View full size.

If you haven’t already, listen to Malcolm’s interview, look at the photogallery of his art and studio, and of course, check out the pieces for sale in the Oten Gallery. In the meantime, a treat for the eye:

photogallery

photogallery

photogallery

photogallery

photogallery

photogallery

Here is a time lapse video showing roughly 90 minutes of stoking in two:
Nice quality, 65 mb, quicktime format.
Dreadful quality, 9.5 mb, quicktime format.

And of course, a photogallery of some of the work from the ninth anagama firing.

Now for the work:

My goodness, it’s been a long time since I posted. I finished up a firing at the end of March and then completely lost my motivation. I must have stoked the last of my energy into the kiln and honestly, I’m still waiting for it to come back — I’m burnt out. Even sitting down to write this entry is painful and I’ve been procrastinating for a month (!) despite the successful character of the last firing. I lament my lost motivation.

{… OK, let’s just do this …}

Overall, the ninth firing truly was good. I’m not 100% happy with the coloring or surface texture, but I’m satisfied for the most part. I received some nice pieces, had no shelf collapses, and internalized an important lesson. The firing can be summed up in three basic topics:

• I finally know exactly how to make the temperature climb like a rocket.
• However, I need to modify air inlet size, wood mixture, or both for brighter colors and
• I need to work on my closing procedures.

Stoking One Stick:

Furutani wrote that sometimes during a firing, the temperature of the kiln can be perfectly adjusted with a single piece of firewood. Even though I’ve read that line a dozen or more times, it was only in the last firing that I actually put it into practice. The effect was astounding and the technique eminently simple: stoke one piece of firewood, watch the chimney till the glow at its tip died, repeat.

The stoking cycle was about one smallish piece every two minutes. I don’t know what temperature I hit, but the light from the kiln was blinding. It was blinding even with sunglasses behind welding goggles. It was like staring at the sun; a sort of fear inducing “holy cow — my bricks are gonna melt” kind of hot. Hot enough that I could imagine the devil requesting my consulting services when things get cool down south.

In retrospect, it makes perfect sense — firing the kiln is an exercise in finding the perfect fuel/air mixture. Anyone who has read anything about combustive firings (no matter what the fuel is) has heard that it is hard to raise the temperature in a reduction environment. I know I’ve read that all over the place — Furtani, Olsen, and from probably a half dozen other writers. Sometimes though, reading is not the same as knowing. After directly observing the effect of hitting the fuel/air sweetspot, I finally “know” this fact viscerally. I won’t forget.

Brightening colors:

As for the color of the glaze, it is less bright than the seventh firing’s results — there was less orange and more brown in this last firing. Early in the firing, I held the kiln in a reduction environment to build up a carbon layer on the pots. While it gave me some interesting glaze lines, and effects, I think I prefer a cleaner brighter look.

The carbon effect shows up In this example:

View Photogallery

This piece appears to have collected carbon soot. When the glaze layer formed and liquified, it caused the soot to streak. Once the glaze built to a certain level, it seems to have flowed separately from the carbon layer, particularly on the neck. This effect works well with my notions of fire as water. It’s as if a winter rain partially cleaned a soot coated object before freezing into a glaze of ice.

While I think I might like this effect, it doesn’t change the fact that many of the pieces were mud-toned. By the same token, it usually takes me about 6 months or so to really evaluate whether I like something … except for those truly awful pieces which are almost immediately subjected to hammer justice.

Aside from carbon, another possible factor in the muddy colors was my fuel composition. In firings seven and eight, I used mostly softwood for fuel. In the last firing, I used a 50/50 mix of hard and soft woods. I think I’ll try bumping up the ratio to 25/75, hard/soft because it may be that the type of fuel has a stong effect on the reds.

As for why this difference may exist, I have no answer — only some guesses. It may simply be that hardwood is denser and thus one armload of alder and birch is the same as throwing in 1.3 armloads of fir. In that case, it would be a simple matter of too much carbon causing the darkening. Or it could be that the there is a different chemical reaction from soft wood flame than that from hard wood. I suppose a better test would be to continue with a 50/50 blend but stoke less when stoking hard woods. My gut is telling me to change the wood though … yet my gut is often wrong.

Closing Procedures:

One easily corrected mistake I made was in cooling the kiln. This mistake caused me much anguish for the week I waited for the kiln to cool. The answer is to use an alarm clock. Here’s the issue:
I like to have a glaze that is semi-matte with glossy areas. I am not so attracted to extremely dry glaze. A surefire way to build gloss is to quick cool the kiln. In the seventh firing, I quickly cooled for about 90 minutes. In the eighth, about one hour.

In the ninth firing, I decided to go for a full two hour quick cooling period. Around 1:00 am, I capped the chimney, closed off the lower air inlets, but left the stoking door wide open. I then struggled to stay awake for two hours at which time I closed the stoke door but did not immediately seal the kiln with clay slip. What I wanted to do was cool for another hour at a moderate pace to let the coal bed reduce itself, yet not drop the temperature so much that it was impossible for a certain amount of matte glaze would to form (matte glaze forms when crystals grow in the glass — a process requiring time).

To repeat, my plan was to wait one more hour, and then completely seal the kiln.

Six hours later I woke up in a panic!

As a result of the excessively quick cooling, the pottery is excessively glossy and there is very little matte glaze at all. This drastic cooling may also have played a role in the lack of any of the brighter orange tones. There is absolutely no orange on any piece I pull out during the firing, rather, those pieces that cool from kiln to ambient temperature in a 30 minute period are very glossy, but completely lack red or brown tones.

Anyway, for not using an alarm clock, I swore at myself for days.

Download the episode directly or through iTunes (mp3, 60:00, 55mb).

Note: The iTunes link requires iTunes to be installed on your computer. If you do not have iTunes, use the “direct” link — it is probably most convenient to right click the link, choose “save as” from the context menu, and then listen to the file in your preferred player after it has downloaded.

Update: Simon now has work available for sale in the Oten Gallery Shop.

Simon was consumed by wood fire pottery to such an extent, it overwhelmed his original aspirations for a legal career. Choosing instead to become an artist devoted to capturing the imprint of flame in his work, Simon has had remarkable success.

Photo gallery of Simon’s work.

Simon’s pottery is beautiful, and springs from his deep understanding of wood fired kilns and his thoughtful technique with clay. The years he has spent learning to build and fire wood kilns has clearly paid off in his work as can be seen in the photo gallery related to this podcast, and at his online shop. There is more to Simon however, then the pottery he produces. There is an intellect and understanding behind the work which takes his skill to strange and wonderful places.

Simon built a wood fired kiln in East Timor in order to enable local production of water filtration equipment. In essence, he turned his knowledge of wood fired ceramic art, and pointed it toward the production of potable water for an entire village. There is a social beauty in the fact that Simon’s understanding of wood firing has directly and fundamentally improved living conditions for many people.

In addition to the East Timor kiln, Simon has built anagamas at Mill Creek, Southern Illinois University (Edwardsville), Corning Community College (see the entry on Fred Herbst), and Syracuse University.

Simon has published a number of articles, many of which deal with developing a philosophy toward ceramic art. During the podcast, he discusses how philosophy and metaphor can be helpful in guiding one’s work, and suggests methods for sparking new ideas or refining old ones.

In truth, there was barely enough time in the allotted hour and some topics were necessarily left out. For example:

• Simon has an online store showcasing his ceramic art.
• Simon is hosting a wood fire workshop with Linda Christianson (additional info) in Kentucky from March 8-13, 2007.
• And of course, there is Adobe who provides kiln dog balance to the kiln’s cats here.

I opened the anagama on Friday night (Dec. 29, 2006) after a cooling period a few hours shy of seven days. I had planned to wait until Saturday morning, but with visions of shizenyu dancing in my head, anticipation got the best of me and I unbricked the door about 15 hours early.

It was a difficult night however, and much unlike the seventh firing in which I pulled out many lovely pieces. Once I peeked into the kiln, my initial anticipation and excitement immediately gave way to despair and dismay, although several small finds allowed my spirits to rebound to some degree.

That which was right:

One idea that worked out wonderfully was “shielding”. By “shielding”, I mean setting up a wall of clay very near to a piece. In this way, the shield would absorb the ash and flame that would otherwise strike the front and melt into glaze. By making the shield incompletely cover the front, I hoped to have shizenyu mixed with hi iro (”fire color”). As this example shows, the result is wonderful:

enlarge

Sadly, I’m not that skilled with slabs so this vase separated at the seams. Still, with a little practice slab building, this technique could result in stunning pieces.

Here is a picture with the shield up — two notes: 1) I broke the shield trying to knock off a piece of stuck wadding, and 2) it was placed much closer to the piece during the actual firing than is shown in this picture:

enlarge

Another winner was this coil built bottle. I made an ad hoc shield out of wadding while loading. The shield wasn’t as close as the one on the brick shaped vase, and it only shielded the foot area, but it helped to some degree:

enlarge

One last pottery picture for the blog (see the photo album for more pictures) — the tube of this bottle was slab built and the base and cap thrown. It was plainly caught in a complicated eddy in the fire path:

enlarge

That which was wrong:

I’m very happy I recorded my firing. My general sleepiness makes memory of any firing rather fuzzy. This time however, I can hear myself making lousy decisions. The most embarrassing is probably my “olivine segment”.

Beware the midnight inspiration.

In a misplaced attempt to enhance green colors in the glaze, I induced a reduction environment toward the end of the firing. Lost in a haze of sleepy logic, I suddenly had the idea that olivine and reduction are related. I did no research, no real thinking — I just ran with the conclusion. Indeed, the wikipedia entry for olivine suggests that the green in olivine is not from reduced iron at all: “Olivine is usually named for its typically olive-green color (thought to be a result of traces of nickel), though it may alter to a reddish color from the oxidation of iron.”

Certainly a “red olivine” from oxidized iron, while not green of course, would be quite nice to have on the hi iro pieces. Besides, the glaze never has difficulty turning olive green wherever it is thick or puddles. Take my mistake as a warning, midnight inspirations should be examined in the light of day — do not simply “decide and do”.

Reduction is overrated … (probably).

It seems everyone talks about reduction but I’m seriously beginning to think that reduction is overrated. What did I get after making certain I wastefully pumped a metric ton of carbon through the kiln and out the chimney? A generous amount of muddy glaze with black halos in the transition areas (by “transition areas”, I mean the areas between the exposed-side and the protected-side).

I’ve tried firings that are more on the reduction side and firings that are more on the oxidation side of things. Not all the oxidation firings have been a success, but all the reduction firings have been either mostly or purely atrocious. Look at this picture from the third firing:

enlarge

After the pottery from the third firing was hammered down into small chunks, it made a decent aggregate when mixed with cement, but there are cheaper and easier ways to get gravel. There was absolutely nothing good about the third firing. In fact, my firings only began to improve once I began letting the kiln breathe.

Although not as disgusting as the third firing, the initial view from this firing brought flashbacks of horrid memories. My initial despair should be quite understandable:

enlarge

So in the end, while every talks about reduction environments, I think reduction does not fit with my preferences. I’m not saying it’s the wrong thing to do — just that I never like the results.

Lose the cones again.

Another thing I must do, is misplace the cones again. I think they lulled me into a false sense of completion. The cone packs I could see said the kiln was finished — cone 11 was laid flat. In the very back however, cone 10 never budged. The sight of a puddling cone 11 toward the middle-front of the kiln affected my judgment, even if subconsciously.

Plan for the ninth firing:

Quick cooling.

It sounds so counterintuitive — after spending days stoking the kiln to ever higher temperatures, does it really make sense to open up all the ports (air inlets and stoke hole), and allow cold outside air to flow freely through the kiln? The proof is in the finished product however. No firing was better (glaze-wise) than the sixth. At the end of the sixth firing, I left the kiln wide open for almost two hours. Had the shelves stood — it would have been amazing.

Although it is psychologically difficult to walk away and let the kiln breathe massive quantities of cold air, I will build up my resilience to this backwards-seeming idea. The ninth firing will feature a quick cooling period of at least one hour — longer if I can stand it.

Firewood.

Finally, I think I need to start using more alder again. In the last two firings, I have used fir almost exclusively. Fir is light and fast burning but its heat seems to have difficulty reaching the back of the kiln. Alder burns quickly like a softwood, but it is slightly denser and tends to hold temperature a little better. Secondly, because alder is denser, it has more “stuff” in it on a log-for-log basis compared to fir. In other words, one cord of alder should deposit more glaze making ash than one cord of fir. Between these two advantages, I’ll try to make my next firing based on alder, though trimmed with fir perhaps.

For now though, it’s time to begin preparing pieces for the next firing. After my initial shock, I’m now ready to move forward and eager to avoid the mistakes of the eighth firing. I especially want to experiment with slabs and methods of directing the flow of ash and flame.

Fred Herbst is a ceramics professor at Corning Community College in upstate New York. Interestingly, google satellite data for Corning is quite good although the kiln had not yet been built in this shot: aerial view of Fred’s anagama site. Check out Fred’s online gallery for a closer view.

Fred Herbst and daughter Emma.

During our discussion, we spoke about Fred’s anagama and one of the more unusual ways in which an anagama may be used: as a furnace for glass blowing. We then move into his experiences with reduction cooling experiments and how this technique benefits iron rich stonewares, but how a more oxidizing atmosphere tends to favor porcelain and white stoneware.

In the photo gallery accompanying this podcast, you will find pictures of Fred’s kiln, its construction, firing, and examples of the finished work. Fred has also graciously provided a set of clay and glaze recipes. Pay particular note to Fred’s Porcelaineous which fires beautifully — much like a Shigaraki clay.

If you wish to fire with Fred, you’re in luck. He is hosting a summer workshop, July 10-16, 2007, with Jody Johnstone. The cost is $200 and if you are interested, contact Fred (email below). If you can’t make the firing but find you are interested in having a piece fired in Fred’s anagama, contact him directly: herbstNO@JUNKcorning-cc.edu (remove “NO” and “JUNK” for correct email).

Last, some links related to topics brought up in our discussion:

• Dick Lehman’s article: A New Approach to Long-fire Results.
• Fred’s kiln was designed by Simon Levin.
• Some history about Roman Glass, the type of glass that was recreated in the anagama glass blowing experiment.

Image courtesy of Arthur Rosser.

Steve Harrison is a potter from Australia with decades of woodfire experience under his belt, plus an obvious love and ability for the geological sciences as applied to ceramics. To understand the breadth of his experience, take a peek at his CV, or consider that he is currently firing work in a kiln he built himself out of bricks that he made from local materials; the pottery fired in the kiln is made of clay he collects locally, glazed with materials he collects locally, and fired with wood grown locally.

photo gallery of Steve Harrison’s work, bricks, and kilns. Photo courtesy Michael Bradfield.

His work is shown (and available for sale) at the Legge Gallery in Sydney Australia. During the course of the podcast, Steve discusses his current show “Dirty Little Secrets” and how he developed the clay body used to create these examples of black-bodied ware (as well the white porcelain work represented in a prior show “From the Ground Up“). His recent work is influenced by the way “perfection” has been devalued by modern manufacturing techniques. You can read more in an article he wrote entitled: Perfect Is the New Junk (pdf, © Steve Harrison, used here with permission).

Steve’s kiln building/rock glaze books are available directly from him. Additional photos of his studio, kilns, and work can be seen on his Sidestoke page. Lastly after talking with Steve, I had much to google. Here are some of the more interesting things I picked up:

• Steve has an article in Ceramic Review, Issue #222, entitled: From the Ground Up.
• Porcelain Spy: Père d’Entrecolles. Read translations of his actual letters or a summary written by the NBH (Hungarian Spies) entitled: Pioneers of Industrial Espionage. (as an aside, the entire NBH site is rather interesting, even if a bit chilling).
• Porcelain requires Baitunze (also spelled petuntse, petunse, baidunzi, and likely more).
• Picture of “treacherous” bauxite pebbles (scroll down for a picture of a hand full of them).

I think you will find that Steve’s interview, aside from being interesting and entertaining (Steve has a great sense of humor), will foment a storm of ideas. Enjoy.