After taking out the primary heat exchanger and using just the secondary heat exchanger, we tested the kiln again.
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| Here's a picture of the kiln when it was firing. The red flames are coming out of little spy holes built into the top and side of the kiln for the sake of monitoring progress during the firing. This is normal during a firing, especially right after a stoking. |
We reached cone 9 (about 1260 degrees Celsius) in about 17 hours.
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High Temperature Cones used: Cone 6, 8, 9, 10
The melted black ones in the front cone pack are the low temperature cones for monitoring progress earlier in the firing The low-temperature cones started dropping at around 6 - 8 hrs into the firing. |
Around cone 9, I tried to adjust the oil drip to get a little more clear burn, and something went wrong and the kiln dropped from a yellow-white color back down to an orange color - a drop of several cones worth of temperature. At that point I decided cone 9 was good enough, and that it probably wasn't worth spending the extra wood for a few more hours to try to get the last little bit to cone 10.
The glaze tests generated some interesting results, and the some of the clay body tests yielded surprising results too. A dark brown clay that we have here turned out to be some kind of nice iron-bearing stoneware. It is really plastic and I thought that it would melt, but it seemed to handle the heat really well. The TPI white clay seems to be a little over-fired at cone 9 - it might make for a nice cone 6 clay.
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Line Blend between the white clay and dark clay. I thought the dark clay would melt, but it turns out to be a nice iron-bearing stoneware clay, and not an earthenware after all.
The tile on the far right is what I am calling TBR #3 Dark Stoneware. |
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| The little saggars I made from the white TPI clay for stacking the test tiles. The white clay warped. |
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Glaze Test Results:
The kiln was loaded with 3 sets of glaze tests. The glaze tests are all made of a combination of rice husk ash (high in silica), wood ash (high in fluxes like calcium, sodium, or potassium), and a clay (either the TPI white clay like the kind that made the warped saggar above, or a gray fireclay from TBR, or the dark stoneware from TBR clay #3).
Glaze Tests using TPI White Clay
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| Triaxial Blend of Glaze Tests using Wood Ash, Rice Husk Ash, and TPI White Clay (same as the warped saggars) |
Glaze Tests using TBR Fireclay (from near the banana garden)
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| Triaxial Blend of Glaze Tests using Wood Ash, Rice Husk Ash, and TBR Fireclay |
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Glaze Tests using TBR Dark Clay #3
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| Triaxial Blend of Glaze Tests using Wood Ash, Rice Husk Ash, and TBR Clay #3 (the dark stoneware) |
