Tuesday, June 25, 2013

Mistakes Firing other People's Work

Last Saturday I taught a workshop for Larson Gallery. It was my last class of 2013, since I will be on sabbatical in the fall and I don't teach during the summer. The class was called "Clay Bells Ring." I had five adults and six kids, plus my own daughter. In an hour and a half everyone made a bell and a few people made other stuff besides.

painting a tiny bell

My daughter was well-behaved and even helpful, though she was one of the youngest. She organized and set out some of the materials, helped me roll some slabs before class and then answered a few questions while I was introducing the project to the class.

rolled texture and sprigs 

The students made the bells by wrapping slabs around paper tubes. Some of the students rolled their own slabs, others used the slabs I had rolled ahead of time. All the students, adults and kids, seemed to really enjoy impressing the wet clay with stamps and rollers. They did this before shaping the bell and after.
stamped texture (on blue) and pinecone rolled texture (on white)

Students used stamps and rollers as well as sprigs (clay molds) and found objects. One of my favorite rolled textures (above right) came from some skinny pinecones we picked up that morning at my friend's house when we went to borrow her toilet paper tubes for the class.

decorating with underglazes
After they formed the bells, students decorated their bells with colored underglazes. At home, after the bells dried, I applied a layer of clear glaze to most of them before firing. 

sharing underglazes

The students seemed to have fun. Everyone made a bell, everyone followed the directions, and a few people even made mugs, containers. or other items after they finished their bells. Unfortunately, I made a mistake in firing the work, so not all of it survived.

finished work at home waiting to dry

At home I let the work dry for most of a week, glazed it and loaded it into the kiln. I set the kiln sitter (the automatic shut-off for the kiln once it reaches temperature) and closed the lid. I planned to fire it the next morning. In the morning, I woke up early and came straight down to the kiln and turned it on. 

fired work after glazing

Unfortunately I must not have been all the way awake when I turned on the kiln because I skipped a step. My home kiln has two dials to control the temperature of the elements that heat the kiln. The dials can be set to "off," "low," "med," or "high." The dials control the temperature, the kiln sitter controls the shut off. When the kiln reaches a certain temperature, a cone in the kiln sitter melts, dropping a metal piece which automatically shuts off the kiln. There is also a timer that will shut off the kiln if time runs out.

kiln sitter (off)

We have this same setup at school. I tell the students to turn the dials to "off" when they turn off the kiln or as they load the kiln even if the kiln sitter is not set yet and the kiln is off. However, I didn't take my own advice at the end of last summer or when I loaded the kiln this time around. I had left the dials on "high" from the last firing (in September). When I woke up early and turned the kiln on, I somehow forgot to check or adjust the dials. Instead of turning the kiln on low to preheat the work for an hour, then gradually turning up the temperature over several hours, I turned the kiln on high right away.


Apparently I woke up completely about 45 minutes later and realized that I hadn't touched the dials in the morning. I rushed in to the kiln to check and discovered that some work had already exploded. I turned off the kiln, removed the bits of clay that were too small to save and replaced the work that was still intact.


As far as I can tell only one piece was completely destroyed and one was broken into more than 4 pieces. Two pieces lost their handles and another piece lost its base. Interestingly, the only pieces damaged were either rather thick (coil handles, etc) or were knocked into something else.

Most of the work survived and fired just fine. Two pieces with handles lost part or all of the handle, but I fired them anyway because I couldn't find the handle pieces. I did some repairs to the piece that lost its bottom and the other piece that was broken into several sections. 

this guy lost his nose and handle

I was surprised that the pieces were so hard to identify after I removed them from the hot kiln. The underglaze, raw clay and glaze all looked the same when hot, though when I loaded the kiln, the underglaze color was visible and the glazed areas looked pink. It was hard to tell where the top or colored section of a piece was. Part of the reason I had to remove the work from the kiln after it exploded (rather than just continuing to fire) was that I didn't know which end was up. If the glaze were at the bottom of the explosion, it would melt and fuse to the shelf during firing. 

underglaze fired without glaze

repaired bell

I will take the work into Larson Gallery today but I am also including a note telling people they can stop by my studio and remake their work if they choose. The pieces I repaired look okay, but the repairs are relatively obvious and there were ones I couldn't repair. I wouldn't want people to feel cheated because I made a sleepy mistake. (On the other hand, I have always thought that a certain percentage of any given clay class population enjoys the explosions. When I used to teach kids classes, a few boys would always ask to blow stuff up.)


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