Front came out beautifully, mid stack as well, rear a little cool. Very top of front, mid, and rear were cold. Shelf config caused this, I think, because of the large shelves being close together, creating strata in the heat gradient. The very front shelf with guinomi and chawan was the main culprit, blocking the flame from rising, and directing it under the large shelves placed midway up the front stack.
In the future I need to stagger the shelf levels during stacking, to allow the flame to travel upward. Also, block some of the floor level flue channels at the rear of the chamber. Make sure upper flues are fully open.
This is one way I make slab plates. I posted the pictures to FB but am reposting here with descriptions of each step. You can adjust the steps if your clay is more or less forgiving than mine.
First cut slabs and let them rest overnight to stiffen up some. These slabs are 10mm thick.
Trim the slab with an undercut bevel, and save the trimmed edges.
Sprinkle something on your form to prevent the clay from sticking. I use corn starch.
Place the trimmed slab bevel side down on your form and paddle it THOROUGHLY, from center to edge, then once more evenly all over. You can use whatever you want as a paddle, here I used a sandbag, but I usually use a wooden paddle.
Place the trimmed edges you saved back on the paddled slab, followed by a paper towel or other cloth, and your board. Turn over the form to release the slab onto the board.
Press the center of the slab down gently and let the edge pieces support the edge of the plate. While supporting the edge with one hand, use the other to define a concavity in the bevel with a convex tool. Anything convex and with a curve you like will work. I used a little ball here. Sometimes I use a rib, sometimes a roller, sometimes a clamshell. I like rollers and balls because they compress the edge well.
Finish and further compress the edge with a damp (not wet) chamois or sponge. Done!
This firing of the kiln went too long, resulting in Orton cone 11 flat. Ideally, it would be cone 11 touching, then sagging a bit.
Upon unloading the kiln this morning, one thing was immediately apparent: the right side was far more reduced than the left. Yellower glazes and more slumping. Even on the left side there was some slumping, because of the excessive temp., and because of the clay which contained some low temp high iron clay to help seal the ware against leakage.
Chosen Karatsu came out pretty good, but the white was on too heavy, running down the pots too much. It still came out looking ok because of the clay.
Most of the teabowls warped or sagged, so I only get to keep 2 or 3 of the 15. This is why teabowls are expensive, kids…
All in all, not a bad firing, but need to adjust clay bodies, and pay closer attention to cones. Also, figure out the over reduction on the right side. It might be that one burner that sounds a bit off.
was a real nail biter. At 4am, 10 hours into the firing, I realized that I had not gauged my propane reserves properly, when I looked at the tanks and realized that they were only about 1/5 full and covered with a thick layer of ice. I immediately put the water hose on them to melt the ice and keep them from freezing again, then I chewed my nails until 8:30 am when I could finally call the gas company for fresh tanks. They arrived just after 9am, and good thing to because I only had about 2 inches of fuel left in the tanks at that point.
The firing ran a total of about 18 hours, which is fairly normal for this type of firing, and most things came out ok, with a few exceptions:
I had to make a batch of slab plates after the fall wood kiln firing, because every one of my slabs cracked in that firing. Turns out the clay I used was high in silica, and didn’t agree with the long wood kiln firing. The silica turned into cristabolite, and all pots made with that clay experienced shivering, or cracking, no matter what glaze they were paired with, and across a range of temperatures.
Forward a few weeks, and I’m frantically trying to get some replacement plates fired because this weekend is the fall open studio event, followed by an exhibition in Nagasaki during the first week of Dec.
For the most part this firing went well, aside from the fact that I exploded my large platter. Drat.