Tag Archives: Pottery

Postfire thoughts

Well, time to sit down with the last firing and figure out what went wrong, and what went right.

Firing and packing: Great. With this firing I figured out, FINALLY, the proper exit flue volume to use. And with it, the proper packing procedure. The kiln climbed steadily, without effort, for 45 hours and the flame in the front chamber reached front to back really nicely. It turned out to be a fairly even gradient from front to back, from cone 13 in front, to a good melted 8 in back. No sidestoking necessary.
I am going to go back to using a pyrometer for the next firing, because this firing got very reduced. I think the stoke intervals were too close, and a pyrometer may help me get a better idea of temp climb timing, and when each cycle goes into oxidation.
At one point, when we switched to stoking the 2nd chamber, the temp just started dropping. You could tell from the sound and color of the kiln. I jabbed a pyro into a peep hole and it told me right away that I was stoking to frequently. After the flame had receded into the chimney and peepholes, and the roar had died away was when the temp really started climbing in the chamber. I had been stoking when the flames receded and the kiln quieted down, but once I started waiting rather for the temp to start dropping after the rise, the kiln got back on track. This rise took longer than I imagined, sometimes up to 10 minutes. Had been stoking waaayyyyyy too much.
This firing was a watershed moment for me, regarding packing, air, and stoking. I think next time will finally be the load that makes us all smile.

Glazes: Glazed ware in the second chamber turned out really nice. Reduction was still too heavy, but we got nice surfaces. Still, I won’t aim for that in the future. Madara glazes were too yellow for my taste. The first chamber glazes were so reduced that whatever their intended color, everything turned out a semi matte green, from the excessive iron pulled from the body saturating the glaze and crystallizing. I think the stoking interval will fix this problem.

Clay body: Oops. Here is where the shit hit the fan. Too much iron, especially considering the temp and amount of reduction that happened. The clay I used for the large pieces has too much iron for that type of firing environment, which is why they almost all collapsed. Having worked with a gas kiln for so long, it is hard to get out of the mindset of adding iron rich clay to other whiter bodies in order to get a desired color. The white clays in this area have enough iron for good color in a wood kiln. I keep forgetting that, but perhaps the shock of this latest meltdown, and the subsequent pain of shelf grinding will serve to jog my memory whenever I’m mixing clay for the wood kiln.

We got this off the shelf in one piece! The attached cup sits level when you set the piece on a table, so great for sashimi and  sauce or condiments.
We got this off the shelf in one piece! The attached cup sits level when you set the piece on a table, so great for sashimi and sauce or condiments.
The Fall of Icarus
The Fall of Icarus
Arm detail
Arm detail

Spring Firing Results

Ok, lots of things to say about this last firing, but with the studio show starting tomorrow I just don’t have time for a long post. Here are pictures instead, commentary and contemplation about these results will follow in a few days…

At long last…

… some pictures of new fired/finished work. Finally got my brightness and white balance issues resolved and took a few pictures to share with everyone.

I hope you enjoy them…

Going with the flow

The last slab of the bunch is the biggest at about 10kg/25lbs. I wanted an ocean motif and started out with ideas for iron brush decoration of waves and ocean birds, with a clear feldspar glaze. Somewhere along the way it changed into two opposing wave patterns, one stamped and the other carved.

The pattern is identical, but the exterior wave pattern was made with my paddle, carved with a wave pattern and used like a bench chisel, placing it on the clay and tapping it with a mallet to create a repeating pattern. The center wave pattern is the same as what is carved into the paddle, but varies more because it follows the changing width of the center swath.

If I can get this one to dry without cracking, it should take the firing ok. It will be glazed in either a white ash glaze or a green ash glaze. A nice runny ash glaze should fill in the texture and accentuate the pattern nicely.

tabula rasa. I haven't decided what to do with this yet. It is double the size of the others, 10kg of clay.
tabula rasa. I haven’t decided what to do with this yet. It is double the size of the others, 10kg of clay.
stamped pattern finished, pattern for carving drawn in.
stamped pattern finished, pattern for carving drawn in.
Carving finished
Carving finished
detail
detail
Edge treatment finished
Edge treatment finished
Detail
Detail
detail
detail

 

The heavy table

I made this table about 5-6 years ago with the intent of using it with guests downstairs in the studio, but as things filled the space I never had a place for it, and it ended up under the staircase for the duration. It had literally never been used  for its originally intended purpose and gathered dust. Until a few days ago when I started rearranging the studio. Now with the stairs out of the way, it is out, clean, and ready for action. I scrubbed off 6 years of dust and crud this morning and started thinking about how best to use it.

If you haven’t noticed already, this is a huge grindstone (one of a pair I acquired), and it must weigh at least 200kg. Somehow I was able to get it up on that railroad tie frame with the heavy duty casters underneath so it can be moved. The current top is actually the bottom, and the actual top is slanted, so one side is propped up on two short kiln stilts so the table top is level. The grooves are close enough together that cups can sit without wobbling or falling over.

It occurred to me that the depression in the center would make a good improvised receptacle for tea goodies, and a garbage can could go under the hole for waste disposal. One other suggestion was to place a bamboo section in the whole as a small waste basket. One of the railroad ties partially overlaps the bottom of the hole, so the bamboo doesn’t fall through.

The freshly scrubbed table, about 80cm/32in in diameter.
The freshly scrubbed table, about 80cm/32in in diameter.
table surface detail
table surface detail
Fresh section of bamboo cut for the waste basket.
Fresh section of bamboo cut for the waste basket.
goodies, with wrapper disposal in place.
goodies, with wrapper disposal in place.
Mmmmm. Nice steamy tea on a cold morning...
Mmmmm. Nice steamy tea on a cold morning…

Snagged a new wheel!

I managed to get my hands on a used wheel, cheap. It is a gigantic banding wheel: wheel head is 50cm across and the whole thing assembled weighs 60kg. It looks like it might have been someone’s homemade wheel, made from acquired parts and put together.

It is an oddly constructed wheel, no bearings at all. The top of the shaft accommodates  a pin in the wheel head like my kickwheel, but there is no bearing in the bottom, just tapered sleeve on the shaft that engages the bottom of the wheelhead shaft, heavily greased. It requires a very fine setting of the tapered sleeve. Engage it too much and the wheel doesn’t turn well, not enough and there is a waggle in the wheel.

It arrived pretty rusty and dirty, looks like it saw a lot of use at some point, then got left in a corner somewhere for a few years. I got a wire brush disc for my angle grinder and spent quite a while getting the accumulation of clay, gunk, paint, and rust off.

Removable wheel head shaft
Removable wheel head shaft
Base shaft
Base shaft
wheel head
wheel head
tapered sleeve
tapered sleeve
The whole shebang, still dirty.
The whole shebang, still dirty.
wheel head assembly oiled and ready.
wheel head assembly oiled and ready.

Finally got the wheel head assembly cleaned up and oiled, and with some experimentation found the ‘sweet spot’ for the tapered sleeve when engaging the wheel head shaft, and the wheel spins quite nicely. Click on the link below to see it spin:
Wheel spin test

My plan for this wheel is to weld arms to the base of the wheel head shaft and mount a wooden fly wheel, and add a wooden wheel head onto the current steel wheel head. The resulting kickwheel should be great for onggi style coil and paddle work.