For those of you that are not familiar with raku, a little bit of information. Raku is an ancient form of firing in which pieces are fired once (bisqued) then glazed and put into a kiln and heated to 1800 degrees. At that point the kiln door is opened and with a pair of tongs the piece is taken red hot from the kiln and put into a container filled with some type of combustible material (straw, paper, leaves, etc.) On contact the material is rapidly heated and ignites.  The piece is then covered with more straw etc., and then a tight fitting lid. Once covered the fire burns the oxygen in the container very quickly and in order to keep burning must take the oxygen it needs from the glaze. This process is what produces the distinctive colors and patterns that are unique to raku.