A great time was had! Set some fires in the alley! No one was seriously harmed! Totally going to do it again!
Raku is a fast-fire technique where you rapidly bring a piece up to about 1800°F and then drop it into a sealable container of flammables. After the initial load we were both loading and unloading into the hot kiln – after about 15-20 minutes for these small pieces you can tell it’s ready to be pulled from the kiln when its glowing red and the glazed surface is shiny and liquid.
Once the hot piece has started a healthy fire, its smothered with the lid and left to reduce for about half and hour. This sealed fire is where the magic happens – once the fire has used up the oxygen in the remaining air it starts to chemically pull it from other sources; The oxides in the glazes give up their oxygen and convert to a more metallic form.
More reading:
Raku FAQs on Ceramics Today
Reduction Firing by Digital Fire