Thursday, March 26, 2009

side stoking covers revisited

Well as the firing gets closer we need to take a second look at our stoke hole covers. For those of you just joining us here is the first round of stoke hole covers. The first version worked alright. They were very easy to handle, and sealed up the hole fairly well. Here they are now:

Unfortunately two things happened. Firstly the large handle slightly warped the circular cover, making them a little oblong. Because of this the covers did not seal up quite as well as we would have liked.
However here is the major problem:

All of the covers cracked from thermal shock. We were still able to use them to finish the first firing, however it's certainly something that needs to be addressed. The first round was made from an equal mix of EPK and kyanite. This time we are going to make them out of a mixture of something around 50 EPK, 30 kyanite, 20 large grog, all this measured by weight. We are then hoping to add some kind of burn out material (sawdust, cornmeal, chicken food, ect...) which we haven't decided on yet. Hopefully this mixture with the more open body from the larger grog and burnout material will be more resistant to thermal shock.

We are still trying to figure out what shape to make the stoke hole covers. The shape from the first round seemed perfect. Certainly they were pleasant to use. I'm not sure how to keep them from warping though. As always suggestions are welcome on this one. One idea is to throw them in one piece with a door knob like piece in the middle. Like an apple baker with a knob in the center. This would certainly be easy to make, though I'm not convinced that they would be as pleasant to use as the originals. I have other ideas bouncing around in my head, but they all seem overly complex. As always I like to wait until the last minute. We should start loading the kiln in a couple of weeks. I guess now would be a good time to mix up the new stoke hole cover clay!


Alex Solla said...

Consider making these from a combination of grog and only enough clay to hold it all together. Throw it with little or no water. That'll help with warping and the grog will aid with thermal shock.

Good luck!

blaine and laura said...

Use somme fire clay in the mixture or all fire clay and grog. that should help. good luck