Pieces are heated up, in this case approximately 1950 degrees Fahrenheit. The artist has to visually confirm the glaze is melting before taking the pieces out of the kiln. Once taken out, the piece is placed in organic material like sawdust, horse hair, or alcohol to create a reduction reaction (a reaction that lacks oxygen). The longer the piece stays in the organic material the more the reaction can occur. In this case, the pieces were taken into a warm water bath to speed cooling but if there is a safe space they can be air cooled.