I found torch firing large diameters of copper exciting and exhilarating and exhausting. The heat needed to keep the copper at a temperature that would allow the enamel to flow was extreme and not very efficient in terms of the gas used, but it did work.
The 1.2 gauge copper was clean, the enamel base of black was the first layer fired. The colours were added with out a great deal of planning, I wanted to know if the size of the piece would fire successfully. Trying to heat the copper evenly, just did not work, I had to wait till the enamel flowed on part of the disc, and then move further along, working my way around. After heating up and the enamel flowed, it was left on the forge to cool within the heated bricks. As I’d worked on smaller practice pieces, I had learnt when the disc needed to be moved quickly to the top of a heated kiln, to allow a long cooling process. Trial and error with a hand wafted over the hearth and the top of the kiln to check the temperatures, taught me when it was time to move. Keeping the disc heated and with a slow cooling time was essential.
I then tried a 35 cm diameter copper disc at 1.6 gauge. This experiment was testing in every way. The heat needed to flow the enamel was extreme and I developed a heat rash on my arms…. after trying to combat the experiment. It became a battle of wills to create the heat needed, keep the copper at the temperature needed and move slowly around the disc. I managed to successfully gain a base layer, which then sprang and chipped and zipped its way off the disc in a pop corn explosion…. the copper just cooled down far too quickly on the hearth and on the kiln top.
I tested torch firing on various gauges of copper and sizes, some warped, predictably. Some enamel colours varied with torch fire, and directing the flame on to the enamel for a short period gave some interesting effects.
These experiments taught me the limits and the freedoms that can be gained from large scale enamel work by torch firing. As I said above, exhausting and exhilarating… but definitely worth revisiting.