Pit firing is an ancient process. Years ago, a fire pit was dug and dried pots were tumble stacked in a mound in the pit. Pottery shards were placed on or near the pots to protect them from the direct flames and cold drafts which cause the pots to break. Combustibles such as wood, pine cones, dried dung and leaves were placed in the pit and on and around the pots. Then the fire is lit. These pots were not bisque fired, like the modern pots of today, so there was much breakage. (Bisque firing strengthens pots, then they can withstand the extremes in temperature that pit firing causes.) Colors ranging from beautiful soft pinks to creamy yellows to smoky blacks can be found on the pots which survived the years and now reside in museums.
Potters have been experimenting with pit firing ever since. Over many years we developed the following process:
We bisque fire our pottery, to minimize our losses. Pottery is left unglazed, as in ancient times, but we occasionally cover some of our pieces with a very thin clay slip coating (terra sigillata) and then burnish (polish with a soft cloth) when dry. Terra sigillata was discovered by the ancient Greeks, who used this process. You can also see the results of their artistry in museums. We make ours by mixing clay in water and allowing the heavier particles to settle. Then we decant the water on top, and use the middle, the terra sigillata. Sometimes we color the terra sigillata with oxides and brush this mixture on. We also use liquid plant food, the organic kind, because it is loaded with wonderful minerals which will help the flames leave colors on our pottery.