Blue flames and broken fingers

Inspired by the pit firing on the Pottery throw down, Nina, Nam and I tried our own smoke firing over Easter with the help of the fabulous Ian Hinchliffe, potter at Quarry Pottery in Corris Craft Centre. We took a similar approach to the oil lamp bin firing Mick Morgan helped us with before the holidays – lining a bin with newspaper then dried wood chopped down as kindling.

The pots were wrapped in copper and steel wire then generously sprinkled with copper carbonate, cobalt oxide, black nickel oxide and a mixture of blue, yellow and pink commercial stains. Dried ferns, pine needles, leaves and banana skin were also added before they were wrapped up in tin foil. Once surrounded by the kindling we set the bin alight though the holes in the bottom and kept adding wood for a good few hours, the metal gradually turning red hot.

More stains, salt and oxides were sprinkled on during the evening, which, if they didn’t make much impact on the surface colours, definitely made for some spectacular electric blue coloured flames for us to watch. The experience of sitting around a fire with a group of people as darkness gently fell over the welsh hills, our shared hopes invested in our kiln babies and mesmerised by the flickering light and warmth of the flames, was an unforgettable experience. The raw power of the flames made me feel connected to something primal. I suppose our early ancestors would have felt the same awe sat around their bonfires at night. Although perhaps it’s just that every potter is a bit of a pyromaniac.

Opening the kiln in the morning, we were surprised to find all the foil burnt away but the pots hadn’t turned as dark as we expected. The colours came out best on the slipcast porcelain vessels with striking flushes of pink and constellations of smokey greys and browns on their smooth surfaces. Burnishing the pots beforehand would have improved the surface quality and leaving them in a reduction atmosphere for longer may have turned the surface darker.

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Reduction Firing

Last week I had the chance to fire some work in a gas kiln for the first time and the results came out today. I don’t know much about how the firing works except that the kiln chamber is starved of oxygen so oxygen is taken away from the metal oxides, but I’d like to learn more. I’m attracted to the unpredictability of the glazes in this kind of firing.

I’d prepared two reduction glazes -the first was a Crystalline pale yellow/green semi-gloss with slight speckle (1280-1300C):

Feldspar                                 37
China clay                              18
Whiting                                   15
Quartz                                      10
Lithium carbonate               9
Titanium oxide                      9
Copper carbonate                 1
Zinc oxide                               1

The feldspar I used was potash and I added Titanium dioxide as a substitute for Titanium oxide. I’ve decided to use small thrown (off the hump) vessels or sections of discarded pots for glaze tests from now on because flat tiles can’t show how much the glaze runs.

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Crystalline yellow/green on Reduction st Thomas

The second reduction glaze I made was a Chun type pale green glaze with crazing:

Potash feldspar                                  45
Quarts                                                    25
Whiting                                                  17
China clay                                              9
Bone ash                                                 2
Dolomite                                                 2
+ Red iron oxide                                    1

The colour was subtler than expected but I like it’s fresh, quiet quality. I find the random speckles of dolomite glazes like this one attractive.

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Chun type green on Reduction st Thomas

Below: Buff stoneware. Two layers of Crystalline yellow/green glaze on outside with Duck egg blue raku glaze circles and Chun glaze inside. I like the roundness of this mug’s base in contrast to the sharper cylinder forms and the pulled handle balances it well.The ribbed texture from drawing up walls inside the form is highlighted by the way the glaze has pooled and draws attention to the way the mug was made on the wheel.

Reduction st Thomas. Duck egg blue raku inside and outside painted with crystalline yellow/green with chun type on top. Painted lines in red iron oxide. The duck egg raku glaze turned out a stunning, vibrant matt blue, I only wish I’d applied it to the outside.

Reduction st Thomas with blue slip splattered on top before bisque. Chun type green painted on outside with red iron oxide lines and turquoise spots. Inside crystalline yellow/green. I enjoy using the surface of vessels as canvases to explore abstract application of slips and glazes. This layering means I get exciting and unexpected results each time although I have to document carefully what I apply.

Buff stoneware cylinder. Inside turquoise stoneware glaze. Outside crystalline yellow/green with duck egg raku over bottom half which has created a cloudy, lichen-esque pattern. Red iron oxide details. The turquoise stoneware glaze turned an almost emerald green and had a bubbled texture.

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4 layers Transparent green stoneware glaze on RsT

 

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Chun type green over crystalline yellow/green

Update: The kiln should have fired for another hour because the cone fell over instead of bending so didn’t reach optimum temperature. The glazes have been underfired which may explain why they didn’t flow much and why the raku blue was so vibrant.