Saturday, January 22, 2011

Kiln Disaster

Here are a couple of photos of the kiln disaster. It was a copper red firing and the bottom octagonal shelf just melted with all the weight on it. This first photo is before anything was unstacked, and you can see that the bottom shelf appears to be missing. It's in there somewhere.

This next one is of a piece of that bottom shelf. Hard to believe it was rated for cone 10, but I have fired those shelves to cone 10 many times, just not with so much weight on them.

This final photo is also of that bottom shelf, the largest piece of all the ones I chipped out. It's stuck to the kiln post, and there is major glaze running.

The shelves above the copper reds were fairly OK. The pots all need to be refired, but they did not collapse as they might have. There is lots of pinholing on the glazes, but I have seen worse come out beautiful in a second firing.

I fired the kiln yesterday to red heat just to make sure the patching was dry -- it has been a month -- and the new target brick, a 12 x 12 x 1 inch slab of alumina, would be able to withstand a burner about 10 inches away and not crack.
The alumina slab came from a friend and it weighs 22 pounds. When I picked up the package I was really surprised by the weight. I was expecting maybe 8 pounds. I've not unstacked it yet so don't know whether the slab is OK.


nick friedman said...

This was probably explained in an earlier post....but why the huge bricks? I'm assuming it has something to do with slowing the cooling of the kiln for glaze development. The shelves STILL should not have collapsed. Have you called the manufacturer?

John Tilton said...

The bricks were a saggar protecting the pots from the flame. They are splits, so they aren't whole bricks. But they ARE heavy. The shelves are so old that I would not know who to contact. I think someone gave them to me many years ago.

I think with all the heat and weight, I just exceeded what the shelves could do. As you can see the other one held up. It was badly warped and had to be thrown away, but it did not collapse.

nick friedman said...

Hey John,

I went for a walk today and for some reason your kiln disaster was still bouncing around in my head. Is there any chance one of the bottom bricks was acting like a target brick that was deflecting the flame into the shelves. Usually the flame coming off a target is WAY more intense than straight off the burner. Just a thought.

John Tilton said...

Hey Nick,

I had a K26 target brick 4.5 x 4.5 x 1.5 above the burner port as a target brick and it had worked fine for a few firings. I just think those thin octagonal cordierite shelves are not able to withstand the weight of the stuff on top. There was probably 100 pounds of stuff on top, what with the hard brick saggar all around, and then pots and shelves above that.

But I am looking for something that will make a good target. My friend Phil send a piece of solid alumina but it cracked in the first firing. It's a nice kiln so I do want to be able to use it.