MudColony

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Mixed Results

I've fired and unloaded my glaze kiln, and entrusted some of the good stuff to Australia Post to take to Shepparton Gallery for me. I got it close to right firing without the pyrometer, but I probably needed to leave the kiln about one hour/20-30 degrees longer as the lower therefore cooler shelves in the kiln were  bit underfired. They'll need to go in again with my next batch. But the top shelves were good. Photos below.

 Impressed with wild geranium leaves, Ash Celadon glaze.

Violet Leaf bowl, ash glaze, a more open form than my previous ones.

Dark clay with an ash glaze. Plate impressed with strawberry leaves, bowl impressed with grape leaf.

Sometimes it's hard saying goodbye to pieces. Especially when you have to post them off A.S.A.P. after unloading the kiln. I hope whoever buys them loves them at least as much as I do. I'm happy with the delicacy of the wild geranium imprints, and the dark clay ash glazes pieces have a very different "ancient" kind of colouring. The contrast between these and the pale ash glaze is striking. The two glazes have very similar recipes but the pale one uses a white clay and a pale processed feldspar while the dark one uses a high iron (dark) clay and a feldspathic rock dust, also with a high iron content.  

Matured Clay

There's an Asian tradition of potters digging clay "for their grandchildren". Clay is not a static material. Once it's sieved and wet down, if you store it for a time bacteria (and fungi too I think) get to work in it and change it's structure. Even commercial clays will improve in their plasticity if stored sealed for a year or two. I've been using clay dug out from under my vegetable patch- quite nice in fired colour but very low plasticity so hard to form and inclined to crumble under my hands. I had a bucket of sieved clay that has been soaking now for 1 1/2- 2 years. Scooped out a handful, dried it to workable consistency and surprise, while it's still a bit temperamental it's much more workable than it used to be. I don't think it would survive being thrown on a wheel but for handforming techniques it's not doing too badly.

The Next Challenge

I want to post off some pottery by Tuesday to Shepparton Art Gallery as they're having a big reopening after renovations and it would be good to have some "fresh" work in their shop for the occasion. This means a no-pyrometer glaze firing for Monday. I have finished a glaze firing previously on observations plus draw trials (rings of glazed clay pulled out via the spyhole to check the glaze "maturity" i.e. has it fused properly) when the batteries in my old pyrometer ran flat unexpectedly. So I know it can be done. It's nice having the reassurance of an electronic device, but for most of history no such thing has existed.

Below are some pics of the pieces I'll be glazing.

Grape leaf plate

 Rockpool plates, impressed with a water eroded rock found on a beach.

Violet leaf small bowls, with the ash from the leaves still sitting inside them.

Weed bowl. I'm planning on only glazing the inside of this with a rock dust Tenmoku (black/brown) glaze.

Mostly Waterproof

Kiln sheds have to be fireproof. Anything that will withstand fire will also withstand water fairly well. Except electronics. 

My pyrometer (temperature sensor) was sitting on a besser block 25 cms above floor level- therefore 15-25 cms below floodline. Dead as a doornail, and with other things on my mind I didn't manage to chase one up from a Melbourne supplier before a looming deadline. But I've been keeping a kiln log, and hooray, I'd put it safely up high! As well as records of time elapsed, gas pressure, air intake, flue adjustments, I'd also made observations of kiln behaviour such as colour changes observed through the spyhole. So I fired without the pyrometer.

I made up four test rings of an earthenware clay and lined them up behind the spyhole. Checked my firing log for a good bisque firing, matched adjustments to the previous records and also compared observations (and took plenty of new ones). According to my notes as the kiln reached the right heat the interior colour moved from cherry red to scarlet, reaching fluoro orange at 1050 deg.C. So at fluoro orange I pulled out a test ring. Lovely colour and a nice vitrified ring when I tapped it. Kiln off, success! 

I won't pretend I wasn't nervous. But a bisque firing has a wide tolerance range for finishing temperature, anything between 900-1100 degrees would do. Even still I was edgy until I'd pulled out the lovely little test ring. :)

"For those who came in late…"

January last year we had one of those events that put routine life on hold for a while. We got flooded.

Water up to 40 cms through most of the house, but my husband's and my workrooms were up a step, about 13 cms higher than the waterline. So they were OK, but the kiln shed had about 40-50 cms of floodwater in it, and my workroom rapidly had a large quantity of books and clothes being rescued from rising water piled into it.

Since then things have been a bit busy, the stuff stayed on my workbench and floor and display cases, the kilnshed stayed silty while I dealt with more immediate day to day needs.

Then I got a phonecall from a newspaper wanting to do a story about my pottery- and I hadn't done any for a year! Took a bit of time for careful thought and prayer, and rang back the reporter to say I'd go with it. That's it, committed to going back to work. So the workbench is clear again, most of the display space is displaying pottery (some still has an impromptu display of rescued books) the kiln shed is partially cleaned (silt scrubbed off vital places, rat's nest removed from kiln)… enough so that I was able to fire a bisque load yesterday.