D Bouchette on mon 23 jul 01
OK, I'm no expert; I've only experienced one Olsen kiln and one firing.
BUT the kiln was built at an Olsen workshop and the firing was under
Fred's direction.
1. The kiln above the fireboxes was mostly built with IFB, not hard
brick. Only the first (bottom) few courses were hard brick. After the
firing, Fred confessed that he was a little bit worried about getting to
cone 10 because of "all" the hard brick in the kiln body. So, a kiln
with walls totally of hard brick might be much harder to fire to temp.
2. Fred was adamant about the design of the fire grates. We built ours
out of 1" steel bars welded not much more than a thumb's width apart.
The idea was to not let the coals fall through to the floor. During our
firing, if I remember right, we did not once have to rake coals out of
the fireboxes. Fred said that this was important to keep enough air
coming into the kiln.
3. Our stack was built of hard brick, 9"x9" inside with a 7.5"x9" input
flue, to a height of the arch or a little higher. Above that we put a
9" steel pipe up another 8 feet at least. Our elevation is only a
couple hundred feet above sea level here.
4. And lastly, the rhythm of stoking in the last few hours was
critical. I admit that the process was getting pretty intense, but we
watched the stack like crazy and if it wasn't flaming high enough, we
stoked. I came away convinced that firing a kiln like that by myself
wasn't something I'd relish...I'd not want to run back and forth between
fireboxes so quickly.
We did make it to cone 10+ on the bottom and cone 11+ on the top on that
first firing.
hope this helps,
Deb Bouchette in Oregon
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