Linda and Charlie Riggs have spread the word on this process. First the pieces are burnished with Terra Sigillatta and bisque fired to ^09 or 1650 F. Pieces are fired in a saggar, or a sealed container holding salts , copper carbonate, steel wool, bronze wool, seaweed, and other combustibles along with the pot. They are fired in a Raku kiln to 1650 degrees F. The temperature is held for 10-20 minutes to assure everything in the saggar has burned. The pieces are removed when cool to touch. Here is a simple method for making Terra Sigillatta.
Saggars are made to accommodate the pots and a 1" clrearance from the surface. Pieces are burnished with terra sigillatta. Sawdust, copper carbonate with salt, and other combustibles are added to the saggar.
Copper wire and wire wool are arranged on the pot and put into the saggar. The saggars are loaded into the raku kiln and fired. When they are cooled, they are unloaded.