Firing in the Rain

Well, normally it is just fine firing my kiln in the rain because here in Oregon it rains a lot but it never rains very hard. So normally when the rain drops hit my hot kiln they evaporate right away. Not today. Today it is POURING! But that's okay because I rigged up an umbrella for my kiln. I also decided to write a song about it. Wanna hear?

A Murder Mystery

Who done it?

Well, I did.


What was the motive?

Really, there wasn't much of a motive. You may have noticed that I didn't make as many blog posts for the month of December. That is because I spent most of the month working on a big fountain. I have always loved making big things out of clay. I have been limited since I stopped taking pottery classes and I no longer have access to the big kilns. This fountain that I made was just barley big enough (once it dried up and shrunk) to fit inside my kiln. Firing it in my kiln was a risk because I have always heard that in a gas kiln your pottery should not be hanging over the kiln shelf, especially during the bisque firing. I had filmed myself making this fountain with hopes of turning the footage into the next "CodyO Show". However, I really wanted to show the working fountain at the end of the show so I am instead going to wait and try again.

How did the murder unfold?

This fountain did not die in vain because there is a valuable lesson learned here that might also help other potters out there who are working with their own electric-to-gas converted kilns. Other potters might have different opinions about what happened here but I think the problem had to do with air flow.

Some might say that I had air bubbles in fountain and that is why it blew up. While that would definitely cause my work to blew up I don't think that was the case here because I have many pieces similar to this fountain that were bisque fired in electric kilns and they did not blow up. Also, I was very careful when making this piece to avoid air bubbles, so I do not think that was the problem here.

Some might also say that I heated up my kiln too fast. However, I have used this same firing schedule for half a dozen successful bisque firings that go way back to even before I started my blog. This piece was the biggest piece I have tried to fire so maybe I should have gone even slower, but still I'm leaning towards air flow as being the problem.

It seems that most times I have blown stuff up in my kiln, it has been due to not having enough space for air flow. Times in the past I have tried to cheat this by putting taller pieces in the kiln that got too close to the top and inhibited the air from circulating evenly around the top. In those cases, the piece closest to the top blew up and all the others fired fine (proving my theory).

In this most recent case I believe the problem was that the base of the fountain was too wide which inhibited the air from flowing around the sides of the kiln evenly. If you look at the picture above you will notice that the side of my piece that got it the worst was the side near the bottom of the picture. This was the side closest to the burner. It would have been fine if the air was able to spiral around my piece like it normally does but the corner of the square base to my fountain was so wide that it blocked the air from flowing around upwards in a clockwise motion. Instead, the one corner got blasted with all the heat until it went boom at about 281 degrees on the pyrometer. After the base blew up I figured that I could keep firing the kiln because at least I would have the top part of the fountain bisqued and I could just make a new base. But, the air was still not circulating around my kiln evenly in a clockwise motion. It was being blocked off by my mostly crumbled fountain base on all sides but one (see the above picture). the heat was being directed just on one side of the top part of my fountain, which soon blew up at 332 degrees.

The evidence (from my kiln data sheet):

How can we prevent unnecessary deaths like this in the future?

Space out pottery evenly in the kiln with 9 inches of space at the bottom, 4 inches of space at the top, and make sure no pottery hangs past the shelves. Let that hot air flow evenly and No cheating!