A couple years ago I hosted a Pit fire for friends and other local Potters. A pit fire is where you burn organic materials on top of your pots in a big bonfire built to get very hot. You Then bury the pots to allow for slow cooling. The effect is a one of a kind earthy hue on the pots. You can control the colors based on what you put in the fire/on the pots. All the attendees brought there pots as well as some material to add to the fire.
in this Firing we used Primarily Banana peels, Walnut shells, Steel wool, Pistachio shells but there was quite the varity from what everyone brought with them