Pit or Saggar Firing Pottery.
Smooth and burnished pieces are traditional for pit firing but you can also have textured pieces. They just won’t have a burnished look. There are several ways to burnish your pieces. One is to use a smooth stone and “rub” the surface of the pot when it is leather hard until a shiny surface is achieved. Very time consuming. The second way is to use terra sigillata, coating the surface of the pot when it is dry (greenware). Then buff the surface with a lint free cloth until it becomes shiny. Be careful not to let the terra sig drip on the surface and avoid scratching the surface.
There are numerous recipes for Terra Sig out there. This is one formulation: 12 cups water, 8 ½ cups OM4 (ball clay), 3 teaspoons sodium silicate. Mix and let sit for 24 hours. The heavy particles settle on the bottom. You want the middle layer. Pour off the water on top, siphon (or pour) off the middle layer. Discard the bottom layer. You will get about a quart of terra sig.
Bisque fire your pieces. Traditionally a low fire, cone 018, is used so the clay is porous and will pick up more color. Firing to 06 is ok. I’ve always bisque fired my pieces to this temp and gotten good color.
Now for the fun part -- prepping and firing. There are numerous was to prepare the pieces for firing. 0ne is to make a saggar by wrapping the pottery in aluminum foil with all the chemicals inside. The other is to place the piece directly into the fire with the chemicals sprinkled around to fume onto the clay. Below is a list of ingredients that can be used. It’s all about experimenting. I suggest doing both techniques.
Two you tube videos to view for specific information are:
1). Saggar Firing Pottery, The Pottery Wheel
2). Pit Firing Pottery with Chris Dunn
The guild will provide some materials for prepping our pieces. These will be available at the pre-preparation session the day before the pitfire: Ferric chloride, copper carbonate, miracle grow, salt, copper spray paint and aluminum foil.
Other items you can provide: seaweed, chore boy copper scrubbing pads, banana skins, corn husks, saw dust, string soaked in salt water, horse hair, copper sulfate, iron sulfate, sugar, copper wire, soda ash, feathers, manganese.
Firing materials are needed; please add what you will bring on the registration form. Wood, from small kindling to medium sized wood scraps or tree branches. Straw. Newspaper to help start the fire.
Other item that will be provided on the day of the firing: Lighter fluid. Raku gloves and tongs. Wax and buffing brush.
Optional firing techniques -- You can fire the saggars in a regular kiln to cone 015, 1382 degrees Fahrenheit, although if using an electric kiln be aware that the salt vapors can corrode your elements over time.