Pit firing or sawdust firing is not a true firing because pots do not reach sintering temperature and need to have been bisque fired before being placed in the pit.
Pit firing will give a range of blacks, browns and tan colors. These colors can be enhanced with the use of oxides, copper wire, banana peels, coffee grounds, seaweed and other organic materials. The effects of the pit firing are also determined by the color and porosity of the clay body.
In a loosely stacked brick enclosure approximately six inches of sawdust is placed, then the pots and organic material is put around the pots. All pots and organic materials are covered with more sawdust. On top of the sawdust is placed a layer of crumpled newspaper. The newspaper is lit in several places and when the flames have died out and the sawdust has started to smolder the pit is covered with sheet metal and left for at least twelve hours.
Twenty-four hours later the pit is opened and the pots are carefully removed. The pots are washed, scrubbed if necessary. When the pots are dry they are waxed. Pit fire wares are for decorative use only and are not to be used to hold food or water.
the pottery division of Northeast Ceramic Supply in Troy, NY