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Firing Log

ancient kiln | 21st century logbook

November 3, 2006

Seventh Firing Results

Filed under: anagama, 7th,Firing,Pieces — odin @ 3:38 pm

The seventh firing is now complete and I feel safe in saying that it was the most successful firing to date. It was not without issues however, and not without some disappointment in my personal performance. By the same token, I am quite satisfied with the pieces I received from this firing. Here is a slide show.

Let’s first discuss my errors because they impacted the firing significantly. There are three:

  • I packed the kiln too tightly in the back.
  • I did not burn enough wood to develop thick glaze.
  • I was too timid with respect to allowing the temperature to rise.

First — there is no excuse for packing the back too tightly. It was sheer greed on my part and had a dramatic impact on the kiln’s draft. The draft was weakened to the extent that I finally experienced a firing in which flames came out of the firemouth during stoking and I must say, it was rather unpleasant — smokey and hot. By the same token, much interesting hi iro came out of the kiln and I can’t help but wonder if a lazy flame is in part responsible.

Secondly — I was aiming for thick glaze. I utterly failed to achieve that goal and the reason is quite simple: I did not give myself adequate time to complete the firing. I closed up the kiln the day before I had to go back to work when in reality, I needed another day or two to fire. Because of time constraints, I only burned three cords of wood and that is simply not sufficient to generate a decent quantity of glaze. To add insult to injury, the wood I used in this firing (mostly all fir), is lighter than hardwoods. Thus the same volume of firewood actually contains less mass and as a consequence, less ash. Plainly, the lack of sufficient glaze allowed the hi iro to shine through so this firing can in no way be considered disastrous, but it was contrary to my intent and thus I failed to achieve my goal.

Finally, I was too timid about the temperature. Earlier in the firing I noted what looked to be a brick that fell from the ceiling — it can be very hard to discern shapes when everything is glowing with its own light — it turned out that I was wrong (a bit of tile wedge from between some bricks had fallen and fooled me). During the firing however, I seriously considered ending when I saw what I thought to be a fallen brick. I decided to risk it instead of quitting. For safety’s sake, I placed kiln shelves over the top of the kiln and rolled fiber out over those. I figured an entire collapse would be unlikely and that this material would likely cover the breach should a partial cave-in occur.

Afterward — I soldiered on but with a newfound timidity. I would push the kiln to white heat, hold it there for half an hour, back off, and then repeat. This seemed reasonable but thinking back, I don’t think I left it at white heat for a sufficient duration. I should have let it go till the glaze on the ceiling started to drip but I let my worry control my actions. While certainly prudent, a part of me feels that I should have taken a more “damn the torpedos” attitude. As a result, there are some pieces with a melon skin surface because they didn’t get sufficiently hot (I personally dislike the melon skin effect), and my sand based clays did not achieve a high enough temperature for the sand to melt on the back sides. On the front — there is some interesting opalescent glaze but the back feels like 80 grit sandpaper. I despise the feeling of sand.

What came out right: the pottery. It’s beautiful — beautiful in spite of my efforts. Perhaps, everything I did “wrong” was exactly what is needed for hi iro. It is worth experimentation — a lazy fire, small amount of firewood, and holding the temperature back might be just the ticket. Still, for the next firing I vow to ensure a strong draft, burn at least four cords of wood (with at least 25% hardwood composition), and let the kiln sit at a white hot temperature for a significantly longer duration. I want my bi-doro and shizenyu!

2 Comments »

  1. Hi, really enjoy your site and I’m glad to be able to read about and see the results of your work. Thanks for sharing it. I have wondered from time to time about the practicality of refiring vessels and I’m curious if woodfire potters ever try to refire their work for a chance at a better glaze effect. Would this be too risky / expensive? Does it obliterate or intensify the prior glaze effect? I ,also, think this firings hi iro results are great. Thanks again.

    Comment by questionman — November 4, 2006 @ 9:47 am

  2. I actually refired two pieces in this last firing with very interesting results and I’m tempted to go for a third firing just to see what happens. I’ll take some pictures soon and post the results.

    Comment by odin — November 5, 2006 @ 11:39 am

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