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Firing Log

ancient kiln | 21st century logbook

May 29, 2007

Podcast: Malcolm Greenwood, From Industrial Manufacturing to Studio Pottery

Filed under: anagama,General,Kiln,Potters,sound & video — odin @ 10:38 pm

In this episode of the Firing Log, I spoke with Malcolm Greenwood, an Australian potter who made the transition from respectable work to full time potter almost two decades ago. Download the episode directly or through iTunes (mp3, 54:40, 50.1 mb).

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 (Aug 23, 2007): Malcolm’s woodfired ceramic art is now available for sale in the Oten Gallery, detailed photogallery here.

Malcolm Greenwood entered adult life with a responsible education and the type of work any mother would wish for he son. After serving an apprenticeship as a fitter and machinist, completing a certificate course in Mechanical Engineering, and earning a degree in Business Administration from the University of Massachusetts in 1976, he was involved with and managed factories engaged in the manufacture of sanitary napkins, surgical instruments, robots, and fasteners. While this work took him to interesting places, including Nigeria, Africa, he never lost the interest in pottery he developed while studying with Mokoto Yabe after completing college (also see this Ceramics Monthly article about Mokoto Yabe, pdf).

In a life changing experience, Malcolm lost his real job and decided to turn his pottery hobby into a livelihood. The year was 1989 and he has been working hard at what he loves ever since. Gas fired glaze ware pays his bills and it is easy to see why it has found favor with chefs and food magazines throughout Australia. When you look at a teapot such the following, thrown off the hump, you are first struck with its lovely shape, and then impressed with the skill it took to throw something so wide without it collapsing:

Example of Malcolm Greenwood's gas fired production ware -- a teapot View Malcolm’s photogallery album.

While his gas fired ware encompasses the majority of his business, Malcolm has been firing with wood for ages. He built a wood fired raku kiln in his college days, and a side-draft kiln while in Nigeria. When he returned to Australia, he participated in the construction and firing of both an anagama and a noborigama which sadly, do not survive to this day (their demise was due to a rent issue, not a technical failure). Malcolm presently woodfires at Sturt, and has achieved some great results:

Wood fired corrugated vase fired at the Sturt anagama View Malcolm’s photogallery album.

wood fired stretched vase fired in the Sturt anagama View Malcolm’s photogallery album.

What interested me most about talking with Malcolm, was the way in which he was able to switch gears and pursue the work he loves. It’s stories like his that encourage me to think that someday, I too could abandon my “day job” and survive as a potter. If you have similar dreams, sit back and listen to Malcolm’s wisdom — he is proof that it is possible.

Some tangents relating to African pottery:

  • Article by Ron du Bois, of Oklahoma State University, discussing his experiences when creating a documentary about potters in Nigeria. Includes a number of pictures of the process and the results. Note that the pictures in the article are thumbnails for larger size shots and the article is two pages long — link to second page at the bottom.
  • Professor Christopher Roy (University of Iowa) has an interesting site purporting to have video clips of various African pottery techniques. Based on other content from the site, these clips may be from Burkina Faso, a country a little to the NW of Nigeria. I haven’t been able to actually get the clips to download, but hopefully that is just a temporary issue.

May 2, 2007

A Single Piece of Firewood / I Stoked the Last of My Energy

Filed under: anagama, 9th,Firing,Pieces,sound & video — odin @ 9:25 pm

Fun first:

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:

Wood fired stoneware vase with sooty glaze effect 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.

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