We hope to fire the wood kiln longer this time, getting more heat to the rear of the kiln and more "heat work" in general. When we visited SU last week they remarked how Jack had fired their anagama long and with little air. Makes sense- if you want to get heat to the rear, lengthen the flame. We have been making slight adjustments to that end as well.
SU's kiln has a very deep and tall firebox relative to the ware chamber. Never quite noticed that before. Although it is a hill climber (stepped chamber), the crown is level. Troy brought hardware for setting up a grate in the fire box. There are a number of pros and cons for this. In the case of the SU kiln, it seems that you would get more flame to the crown which would help draw heat up and over to the back of the chamber. You can get fewer ashes and coals as well. But patience is the key. A longer flame helps keep things even. Pots and bag wall placement/height matter as well. I am not sure about the stoking ports to the rear of the (SU) kiln. It seems they are so far back that you are feeding the stack, not the ware chamber. They are talking about creating an air port for the rear stoking port, but it still seems that you might be doing things a bit late in the chamber (ps- Henry Gernhardt, SU Prof., had suggested an air port in the rear when the kiln was first built- I defer to him!). Noborigamas don't have after burners. And the effects of a "check draft" need to be considered.
Feeding the stack has always been a question for me. A long flame does just that. But an even kiln is usually the goal. The trick is to strike a balance. The stack is a tool, not a chamber. But it is fun and dramatic to "candle" the top of the stack. There is so much to discuss here. We have a "secret chamber" between the main chamber and the stack which we have yet to experiment with. Part of the excitement is the variations in approach. Maybe someone has some ideas to bounce around.
We originally planned a grate on our kiln but opted out. We were tired and wanted to get on with it. We also knew of wood kilns without them that fired fine. I think it is something we will eventually try (our kiln chamber does not step up like SU's- our fire box is lower than the chamber; the crown is level). I do think the coal/ash amounts can be managed either way. One of the first things I learned years ago was not to be so efficient in pulling coals from the fire box. It is tempting- but you are losing valuable btu's.
Air is another issue. A wood kiln is the same as any fossil fuel kiln, but the reads are a bit different. For example, a lot of flame at the ports and damper means reduction in a gas or oil kiln, but not necessarily so with a wood kiln...
At SU they use the same phrase we do- "we are just learning about this kiln." Great fun.
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