First, greenware (dried unfired clay) is coated with a clay slip called terra sigillata (fine clay particles mixed with water) and burnished to a glossy finish. Then the pottery is bisque fired prior to the firings mentioned below. After the final firing, a sealant is applied to the artwork. The following examples show the processes and the results.
Pots are placed in a clay saggar, which is a ceramic boxlike container used to enclose and protect pots inside the kiln. Combustibles, organic materials, and minerals including salt and copper carbonate, along with metals like copper and steel wool, surround the pots. The saggar firing method fires to approximately 1700 ̊F. During the firing, the materials ignite and fume to create dramatic and irregular patterns. Colors range from white to black, and from pink to orange, with flashes of green or the more rare and special bright turquoise.
Foil Saggar Raku
After being saturated with ferric chloride, pots are wrapped in aluminum foil. Additional materials such as steel wool, copper wire, and sugar can be placed on or around the pot. They are then placed in a raku kiln and fired to 1150-1250˚F.
The coloration on these pots comes from the color of terra sigillata and the carbon produced from the smoke. This is a primitive but very effective decorative technique. Pots are either placed on a bed of sawdust and set afire, or placed in a barrel with combustibles and wood embers.