While the throat arch was coming into being, the kiln was growing all around. For the most part the walls are pretty straight forward, except for the mysterious air holes in the front (firebox) wall. Most blueprints seem to have some sort of ‘secondary air’ opening but I couldn’t find much information about placement and quantity of these holes as it relates to their purpose, and hence there was much debate. Especially since the fire in a bourry box kiln is up-side-down, which is where it gets a bit confusing. Because, contrary to what logic would dictate for other situations, primary air needs to come from above the wood. In other words, as far as I can tell from firing the kiln, these holes don’t do much. We only use them in the initial stages of the firing (when the fire is on the floor) and clam them up once we move to the hobs.
Now that I understand the workings of the kiln better (blessed hind-sight again!), I would think of splitting these holes so that the bottom row is about 3 courses lower than it is now (say half way between the firebox floor and the hobs?) and the top row of holes is ABOVE the hobs. Overall, more holes are always better, and we certainly have lots. But placement isn’t insignificant. We have since added more (primary) air holes in the top of the fire-box, but that’s yet to come…
