Tuesday, December 18, 2007

Wood kiln II

The taking apart and rebuilding went to plan. I now had a kiln proportioned correctly on the length and width axis. The height axis was causing me problems, as using the two different types of brick made it very difficult to ensure that I had the correct ratio of firebox to chamber. Even so, at some point in the building I decided against the side opening for loading and unloading of the kiln for a number of reasons. The main reason was the odd proportions of the firebricks I am using, meaning that I had to lay two courses for each one in the plan to make the overall ratios of length to width to height fit. To avoid brining in weaknesses to the structure, I decided against exact doubling up of the bricks keeping the half-step building style going. The photos show the mock-up from the first day's efforts - to give an idea of the problem (four "half" bricks needed in the alternating layers).

I decided to do away with the side hole and make all the packing and unpacking from the top, which I would seal over with clay before the firing starts. Seeing as I had a number of firebricks left over I also increased the height of the chamber by one or two rows. Other than this, the kiln is built on the basic plan as given at sidestoke.

In this image the proportions are visible. I have replaced the normal bricks with firebricks for the grate to give a bit more room for the stoking process. I also like the idea of the sideways bricks in course 3. They should give a nice amount of air to the firebox - so it is not all bad that I did not have firebricks for the whole kiln.

My proportions are:
ashpit and firebox two courses high: 16cm each.
chamber is 9 courses high: 36cm

The chamber to firebox to ash-pit ratio in my kiln is therefore 9:4:4
The original plans call for a ratio of: 4:2:2

I am wondering whether this will make a difference or whether I should move a course down below the kiln floor, to make for a bigger firebox and smaller chamber.

My chimney is also a few courses shorter than the plan. If people think that I should lengthen it (with a metal tube or something) I will do so. It is meant to be 8 courses (16 of the half bricks) and it is only 6 (12 half bricks).

Finally, I have this back view of the finished kiln.

Feel free to make comments.

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