These pot get their surface decoration by smoke and other materials rather than glaze. The pieces are placed in a metal trash barrel filled with sawdust and often random materials to leave surface markings (copper wire, salt, ferns and leaves). The pots are dispersed throughout, and the top of the sawdust is lit on fire. It burns for 15-30 minutes, then the flame goes out and the barrel continues to smolder. The way the smoke moves through the barrel and around the pots leaves the markings you see.
This piece was fired on a bed of wild ferns that grow near my studio, leaving an image on the ceramic surface. There are also some beautiful brown and tan areas, places where the smoke left nice variations. There are also the random marks left by the smoke swirling around the pot. Every side is very unique and interesting to observe.
Be sure to check out one of my sawdust pots on page 125 of Mastering Raku, Lark Publications next time you're at the library or book shop!