Raku, Saggar and Pit fires are three alternatives firings that involve smoke as main part of the decoration.
For the Raku fire a glazed pot stays in a kiln until the glaze is starting to melt, immediately the pot is loaded in a closed container with combustive materials like paper, or leaves. These materials catch fire and inlay the smoke producing a special effect on the glazed pot.
Saggar fire is done with pots with no glaze; the pot is stored in a closed container with combustible materials like sawdust and paper. Chemicals like copper might be included in the container to produce orange or red flashes. The container is put inside a kiln and fire for a few hours. The pot absorbs the smoke produced inside the container along with any chemical making interesting markings.
Pit Fire is when a bisque pot is placed in a pit or trash can full of paper and saw dust. The combustive materials are lit and the pieces stay inside the pit for a day or two until they are cool enough to remove. The smoke inside the pit produces the dark areas on the surface while the oxygen keeps the white areas on the pieces.