Here are the results of the July 26th cone 6 range firing of brush decorated work with feldspar/ash glazing. There is a definite oxidation/reduction line from left to right the higher up in the kiln you go.
Top level pretty much everything is oxidized on the left and reduced on the right. This slowly moves toward oxidation in a left to right, front to back direction as one moves towards the bottom of the stack.
I'm not sure why this atmosphere irregularity is occurring. There seems to be enough space around and under the stack, and between the shelves. Possible reasons I can think of now:
1 Blockage in the flues of the car
2 Air getting in around the door seal on the left side
3 Burners on the left or right need their primary air adjusted
4 Burners on the on left or right may have some blockage
Aside from the above possible reasons for the irregularity, I don't see how any reduction was possible at all since I did the entire firing above 900C very solidly in the oxidation range. The stack was stacked very evenly from left to right and it seems unlikely that
the pots themselves contributed to bad air flow.
Before the next firing I need to get in the kiln, have someone close and tighten the door, then see if any light is getting in through the seal. Also, adjust the right side burners for a little more primary air.
Biwairo still a little weak because of the clay. Even with Karatsu Aka, some more iron needs to be added to get more color in the gas kiln. (Not necessary to add for the wood kiln)
The Utah iron pigment is very nice color with 5% bengara and 4% kurohama added, and the glaze does not crawl badly over it.
Might need to add another 3-5% ash to the kairagi glaze, as it seems a bit too opaque white when thick. (maybe try again on more red clay body before adjusting this?)
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