Letting the glaze dry for several days before firing enhances the crystal growth. By using an oxygen probe, I can control the amount of reduction during all stages of firing. To determine when to begin reduction, I place a Cone 010 at the end of my cone pack, adding a small depression to catch the melting cone. About 40 minutes of reduction is necessary to achieve good carbon trapping. I close the damper slightly, close down my primary air, and add small pieces of wood to the chamber.
Back pressure sends a light cloud of carbon into the room.
Typically, my oxygen probe reads about .08, and that is heavy reduction. The wood addition may be more mystical than scientific, but I do it anyway. I keep the probe reading at about .06, until Cone 10 starts over. At this point, I clear the kiln of carbon and continue to fire to Cone 11 bending. This last phase must be watched closely, as it happens quickly.