PIT FIRE PROCESS
The pottery is left unglazed, as it was thousands of years ago. We decorate the surface of each pot with a variety of materials: terra sigillata, copper and salt wash or cobalt and salt wash, plant foods (liquid and crunchy), and other minerals and oxides. Terra sigillata (stamped earth) was used by Greek & Roman potters to make the surface of their urns shiny and to provide a very temporary waterproofing for cooking pots. Clay is mixed in water and the particles settle for several days. After decanting the water from the top, the section with the smallest clay particles suspended in the center is removed. We wait until the application has dried and then polish it softly. A glow appears almost immediately which remains after the pit firing.
We have 2 30”x 60”x 30” pits which are actually above the ground because there is very little topsoil in Door County. We used old firebricks with one and hard bricks with the other. We made the pits smaller because we fire them weekly.
First the pit is filled with 4-6” of sawdust. It is then lined with pine slab wood, which burns the hottest. Salts (table, sea, water softener, de-icer), oxides (cobalt, copper, iron), organic materials, which contain minerals, (dry dog/cat food, dried banana skins, coffee grounds, pine cones, cherry pits, sticks, leaves, dried bunny manure, walnut shells) are sprinkled on the bed of sawdust before the pots are loaded into the pit. All of these are transformed into gases when burned, combine and then alter the surface of the pottery, which are also treated.
Pots are tumble stacked, or leaning into each other and resting on top of each other. We can get away with this because there is no glaze on the pots, and therefore no risk of pots sticking to each other. Instead, each pot’s decoration and surface treatments affect each other. We then begin to build a bonfire on top of the pottery, starting with small pieces of scrap wood. We then twist newspaper and stick it into the spaces and then put another layer of wood, larger pieces now, and then more paper and then finally, the last layer of wood. John dribbles an orchard mix on the top layer and then lights the bonfire.
We let the fire burn hot for 30-45 minutes and then cover the pit using old kiln shelves, reducing the amount of air and causing the firing to go into reduction, which helps develop colors. The fire takes between 6-8 hours to burn completely down and it’s safe to open it up. Once the ashes are brushed off, the pots are scrubbed clean and then allowed to dry. A final application with a water based poly preserves the surface and gives it a slight glow.
Pit fired pottery is decorative, so use dried arrangements. Hairline cracks are evidence of the firing process, as are the marks of the flame left on the surface.