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.

Enamelling

In a similar way to how glaze powder is fused into glass on ceramic, enamel powders are fused onto copper. The temperature however is a lot lower, any higher than 800C and the enamel starts to discolour, as I soon found out.
Before and after shaping the copper needs annealing and then plunging in cold water to cool. Gum arabic is painted onto the back of the shape after cleaning, then backing enamel is dusted on top and the copper placed in a small kiln. When opened the kiln temperature plunges and you have to keep an eye on it as it gradually climbs back up to 799C. On the opposite surface different coloured enamels are fused on in separate firings, although the process is a bit more difficult than I expected. The colours don’t behave as planned, burning out before the kiln reaches optimum temperature or leaving speckled textures (which can look nice – a bit like a dusting of snow).
I’d like to know if these copper enamels can be used on top of bisqued or glazed clay. Alternatively, perhaps panels of enamelled copper (maybe a maker’s mark) could be inlaid into the clay after firing by being stuck on, although I’d have to contest with shrinkage.