Third Firing .... June 1st, 2000
Kiln Log Book
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The second firing had taught us more about wood types and ash, about stoking rhythm and wood management, etc. For our third firing we wanted to try to duplicate the excellent ash build-up of the second firing, improve the loading of the kiln to provide a more even flow path and heat distribution, and manage ourselves and the work area to create less chaos.
During the two months between the second and third firing we had discussed mostly the things that irritated us ... too many people created make-work and lost souls, wood ended up being piled all around and was a safety hazard, the stoking technique (or lack of) had done some damage to the kiln as long pieces (up to 4') were put into the stoke holes.
We had gotten two enormous loads of 4' long (mostly) oak 2x4's from a pallet recycling shop in Eugene and had taken the time to saw them all in half. We had created specific areas for stacking wood near the kiln and had pre-loaded these areas with considerable wood. We had decided to use cedar (old/used shingles and fencing) to start the fire and to stoke for the first few hours. This in conjunction with constant "fluffing" of the coal bed in the main firebox would provide a large amount of ash in the critical early hours.
In order to ensure we had enough ware to fill both chambers and allow for a more consistent, balanced load we had opened up the firing to other potters at Club Mud (the clay co-op we belong to in Eugene). However, we had also cut down the number of people who would actually be at the firing to the six (sort-of) original builders. We divided all the wares into one table of pieces for the second/salt chamber and another for the first. We took more time to study the pieces and plan (what a concept) how the actual load of the chamber would go.
The time spent in loading was well worth the effort. In the end we had both chambers (as can be seen from the photos) fairly well packed. Both chambers had large pieces on the top shelves which by nature created a tendency for the flame path to go across the top. Our experience from the first two firings had told us that we would have to pay special attention to managing the flame path down towards the floor in order to minimize the heat imbalance and ensure even ash layer.
The firing went pretty much as expected ... we had to struggle with some imbalance of heat as with the first two firings, but everything went quite smoothly. We moved from the main firebox to the first chamber firebox (alternating between the two in the beginning) as we worked the heat/flame up through the entire kiln.
Then as the first chamber got to temperature (Cone 9-ish) we began to alternate with the second chamber. Moving then totally to the second chamber while occasionally putting wood in the main firebox and/or first chamber to prevent re-oxidation. We salted the second chamber starting at about Cone-8(ish) and kept this up till we shut down at Cone-10(ish).
The firing went for almost eighteen hours. We mudded all the stoke holes, peeps, and air ports and left the kiln to cool for two days. On Sunday we all (plus some of the people who from Club Mud that had put in pieces - shown in "clean" dress clothes!) arrived to open up the kiln, eat lots of food and drink cold beers as the temperature was in the low 80's.
The salt chamber was still a little hot, so we started unloading the first chamber and were rewarded with some wonderful pieces. During the firing there had been three loud "pops" about 45 minutes into the firing (which confused us since the kiln temperature would have been still low at that time). We discovered that one of the potter's ware, which had been super saturated with soda ash solution, appears to have had trapped air/vapor inside and exploded ... wiping out many other pieces.
All-in-all we were happy with the results. We did have a bit too much ash in some places (mostly in the lower areas of the first chamber) and some larger pieces which were placed on their sides had slumped under the weight (and the Cone-11 at the top). But no one was complaining ...