Raku, aka Post-Fire Reduction, what is it?
While modern Raku firing techniques are similar in some respects to Pit Firing, Smoke Firing and the like, there are fundamental and aesthetically obvious characteristics that place Raku in a category of its own. Due to lack of space as well as a limited attention span on my part, I will concentrate more on explaining (some of) what modern Raku is, as opposed to what it is not.
Rather than a typical long-term firing sequence where pottery remains in a kiln from beginning through final cooling, sometimes 24 hours or longer, modern Raku techniques almost always involve firing times of less than one hour, after which the kiln is opened and red-hot pottery is removed (with tongs or high-heat gloves) and plunged into a reduction chamber containing flammable materials of your choosing. Sawdust, cattle manure or your favorite old Levi’s will work. Combustibles such as gasoline will likely end your life. If gasoline was your first choice, I recommend other forms of artistic expression for you.
At the instant red-hot pottery enters the reduction chamber, fire erupts. The chamber is closed and flames are smothered as all oxygen is consumed. Without oxygen, these super-heated mixtures of un-spent volatile fuels remain suspended at temperatures far above their respective flash points. If the container is opened at this point a flash-fire will result. Unless you are wearing protective gear, you may bid farewell to your eyebrows, but the risk of permanent physical damage is more likely. Above all else, protect your eyes, period.
At this point, your pottery is subjected to tremendous levels of destructive thermal shock. As semi-molten glaze surfaces are freed from the oxidizing effects of oxygen and are bathed in scorching gases, an astonishing transformation begins. The metal oxides, carbonates, etc., (essentially rusts) used as pigments in (my) Raku-specific pottery glazes are morphed back to a metallic state and behave much like oil floating on water. These micro-thin layers of copper, iron, cobalt, etc., are capable of refracting light in an array of color effects that can range from antiquarian to iridescent rainbow, from bright metallic mirror-effects to understated matte finishes. Heat-work & timing variations, as well as alternative techniques including water quenching, can produce such diverse results that exploring the possibilities of even a single glaze recipe can take years.
The transformations that occur during this process still spark debate among physicists, metallurgists and the like, but for those clay artists who risk seeing their work rendered into shards for a chance at glory, it is the unpredictability and the mystery, the failures and successes, the startling beauty of it all that keeps us coming back for more.
A quick note: While obtaining clays designed to withstand the thermal shock associated with Raku firing can be a challenge in some areas, it is becoming more commonplace. Ask your local art supply dealer. In fact, a patient potter will find that almost any clay type can be Raku fired, but I highly recommend Raku-specific clays in the early stages of experimentation.
Now for the disclaimer: I will soon post videos that go into much more detail, especially with regard to throwing techniques and controlling the destructive forces of Post-Fire-Reduction. However, regardless of how much information is obtained from print or online, bear in mind that Raku can be an extremely dangerous endeavor, mistakes very costly. Your first forays should be undertaken with supervision from an experienced practitioner.
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