Luster glazes utilize metal compounds—such as silver nitrate, bismuth oxide, and copper carbonate—to create beautiful, iridescent finishes. To achieve the signature luster effect, pottery must undergo a specialized third firing. During this stage, the kiln undergoes a "post-reduction" reaction: as fuel like methanol burns, it consumes the oxygen in the kiln's atmosphere. Deprived of oxygen, the fire is forced to "steal" oxygen atoms from the metal oxides in the glaze. This reduction process transforms the surface colors—turning pale greens into vibrant copper reds, and cobalt-silver blends from deep blue to bright silver. The result is a magical, shiny, and metallic surface.