Raku firing involves taking a red-hot piece of pottery out of a kiln at just under 1000°C and finishing the pot in a variety of ways while it is hot.  The three main techniques I use include reduction raku, naked raku, and horsehair raku. 

Reduction raku involves placing the red-hot pottery in a chamber of combustibles such as paper or wood chips.  A lid placed on the chamber reduces the oxygen to create a reduction atmosphere resulting in the blackening of raw clay, metallic looking glazes, or glaze crackling on the glazed surface. 

Naked raku is a variation in which a clay slip mixture is applied to the pot before it is placed in the raku kiln.  The slip cracks and breaks apart during the firing and is chipped off after to reveal a blackened crackle pattern. 

Horsehair raku, or sometimes called painting with smoke, involves combustibles like feathers or horsehair burned onto the surface of the red-hot pottery leaving tracings in carbon.