Woodfiring, February 2023
- Date: 2023-02-24
- Tags: #pottery #blog #woodfiring #guppie
This is my third wood firing at Trevor Youngberg's Kiln yard. This kiln, Guppie Gama, is about 60 cubic square feet with two doors: front and side. In this firing, we did not use the side door This picture was taken during closing time when the back pressure pushes out heat from the side door.
Photo Credit: Hiromi Saitoh
He implemented some feedbacks from our previous firing at Beluga Gama. A zigzag shape backwall before the chimney, and the idea from Norwaygian Sutema Design (1). This backwall is efficiently keeps the heat in the chamber while we lose little space in the back.
Mike WetClayWorks brought two thermometers, and configured wireless transmitter so that we can record data on a laptop. Those realtime measurement really helped stoking crew during firing.
I also did some 3-D visualization afterwards Click here for interactive chart / Another Variation
Those visualization in 3-D is mainly my test drive for the data; however, I try to implement accurate flame color scale based on the temperature. 3-D kind help you to rotate around, and you can visually see when back temperature is higher than side one, or vice versa.
Although I missed preheating and closing door time, I participated almost entire phases of woodfiring activity: chopping, loading, firing, and unloading.
We used mostly mixed black locust and pine. At the end, we used red pine. Total duration was three-four days, and it took three days to cool down. The highest temperature was around 2330 F.
Results
After going through a lot of unloaded works, I have to digest different outcomes. First I love the frontline results although excess heat split a jar vertically. It tells a story of aggressive stoking period and how each section in this kiln renders variety in terms of texture of each work.
Another vase, a copper rich glaze (Oribe and Panama Red) work run as I expected. It presented smooth matt natual ash blend on the other side. 3-D printed objects, which are actually functional small dishes Mukouzuke , survived this firing as well.
The yellow salt had beutiful satin texture with inron spot emerged from the red clay body. As I learn more, I was able to start desigining by selecting different claybody and a specific type of glaze.
On the other hand, iron rich clay body (a.k.a Brooklyn Red) didn't like traditional shino. This make sense. More iron on body is equivalent to black iron oxidize underglaze underneath, which eventually cause surface tention and avoid absorbtion when it melts. I would look for crawling effect next time. As for my porcelain slip and shino glaze, I will revisit after cleaning process.
3-D Capture of Guppie Gama
I had an opportunity to capture the Guppie Gama structure. It is not only cool visual effect but it is useful to explain the structure to someone who never seen Anagama. For example, I got interviewed for a podcast series, and I show my screen with this 3-D model to explain how the backwall looks like.
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References
- Jan Christian Hvistendahl's sutema design via Lillann Ulverud