Sheet of 6mm thick float glass slumped over a positive mould using a 2 stage process - getting the glass to fold around the mould at 670 degrees and then giving it 5 minutes at 780 degrees to pick up more of the detail.
While it was still very hot – about 700 degrees – I took it out of the kiln and sprayed it with water to crack it. I then returned it to the kiln and raised the temperature to fuse the cracks and then cooled it gradually to anneal it. After it had cooled, I rubbed a mixture of copper oxide and water into the cracks and roughness on the inside of the mask and fired it again – to make the cracks and surface texture stand out.
I like the result although it’s not what I originally planned. I had wanted to craze the face but fusing healed the smaller cracks. Also, I had expected the copper oxide to create a turquoise colour of a copper salt, not a pink colour of pure copper. It might turn turquoise in time. More experiments beckon!