I got Sumi von Dassow's book on pit firing (Low Fire and Burnishing) and I'm near ready to do my first. Most of my pieces will be white earthenware. I'd like to try to get some of the effects shown in the pot below. The ingrediants are listed as wood shavings, steel wool, copper and salt. From the blue tones, I suspect some cobalt compound was also used, but my question here is, What produced the red/orange tones on the top? Copper? Steel wool? Both? Thanks.