Tag Archives: ceramics

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

A few things…

Well, last weekend’s firing is now unloaded and most everything turned out well. It was all for a wedding, so always good not to have to do it all over again…

Before and after pictures:

Loaded and ready to go...
Loaded and ready to go…
Finished katakuchi, about 25cm wide.
Finished katakuchi, about 25cm wide.
interior detail
interior detail

Next are some teabowls for the next wood firing. Made from some really gnarly clay, I had high hopes for trimming these…..until I forgot about them and they dried out too much to trim! Dag’nabit!

teabowls
teabowls
Guinomi
Guinomi

Have a great week!

Testing new WP functionality

*Testing new blog to FB forwarding app* *New gallery image display format*

 

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…

Slabfest

Sorry to everyone for the lack of posting lately, particularly pictures of results from the last firing. I’ve been taking photos, but keep having to scrap them because the color is all over the place. When I did the remodel of the workshop it totally screwed up the ambient light on the 2nd floor. That, combined with me moving my photo setup downstairs, and my white balance is completely out of whack. So, I will post finished work when I get that all sorted out. It’s looking like I’ll have to move the photo setup back upstairs and go back to dedicated lighting of one type only (at this point all you photographers are thinking “no shit, Sherlock”, no doubt.)

Anyway… back to the slabfest thing. After finishing a lot of pots for a wedding order, I started thinking about slabs, and the fact that I finally figured out how to make them without having them all crack during either drying and/or firing. So this next firing will include thicker and larger slab plates,  and also one experimental interlocking slab wall hanging that will be about 5 ft. tall.

Lately, all my slabs are made by slapping a piece of clay out on the floor until it is the desired thickness. After that, I get them onto a board and paddle the bejeezus out of them. Lastly, the edges get compressed with a damp chamois. On one of my dog walks a couple of years ago, I found an old rusty sickle which I hammered into a curve and now use to facet and flute different pieces. It also works great on these slabs.

smaller slabs all finished and now drying
smaller slabs all finished and now drying

 

edge detail. gouged with a piece of rough pine and smoothed over with a chamois and hands.
edge detail. gouged with a piece of rough pine and smoothed over with a chamois and hands.

IMG00452

surface carved to look like tortoiseshell bamboo.
surface carved to look like tortoiseshell bamboo.
simple fluting
simple fluting

These three do not have raised edges, since they are meant to be a wall hanging.

one of three interlocking slabs.
one of three interlocking slabs.
they will be held together with wooden butterfly keys
they will be held together with wooden butterfly keys
all three will have iron underglaze brush decoration with traditional motifs.
all three will have iron underglaze brush decoration with traditional motifs.
36cm square slab, same size as the others above. This one will be for food, so the edges are raised, and smoothed.
36cm square slab, same size as the others above. This one will be for food, so the edges are raised, and smoothed.
detail of rim and fluted surface
detail of rim and fluted surface
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.

 

A pot only a potter can love…

This last wood kiln firing was a real disaster. All of my large pieces cracked or collapsed completely, and all of the smaller work ended up under-fired badly. The upside to this is that they can all be refired, and I just finished the 2nd of 3 refire loads in the gas kiln this morning.

From the first refire load, my favorite pot is a porcelain teabowl glazed with rice straw ash glaze. I don’t normally work in porcelain, but in my search for bodies that vitrify a little better than the local clays, I’ve started using partly or mostly porcelain in some of my work. This particular bowl is porcelain with as much feldspar sandstone mixed in as I could manage, and still have it wedge-able.

In the wood firing it was in a spot that got a lot of fly ash, and in fact a lot of flaky ash collected inside the bowl. Making sure not to dump this, I saved it for the gas kiln and fired it to cone 11 flat. All of that ash melted really nicely, mixing with the rice straw ash glaze for some nice color.

There are several bloats on the interior, but none really fragile or severe. These bloats and the blues and greens on the interior really remind me of some the old Karatsu bowls with their warty bloated surfaces and subtle coloring of fly ash on rice straw ash glaze. Another nice thing about this pot: the fire color from the wood kiln was not lost in the gas firing. There is a nice gold luster on the  melted surface of the bare porcelain body.