Copper reds are achieved in a reduction atmosphere.  The glaze must have the correct proportions of Tin Oxide and Copper Carbonate. These copper reds were achieved by reducing the kiln at cone 05, approximately 1880 degrees F.  The kiln is held in reduction until 2100 degrees F or so and then a mild reduction until the kiln reaches a final firing temperature of 2380 degrees F.  At peak temperature, the kiln is pushed into a heavy reduction, essentially stalling the kiln and providing a time to even the firing and smooth the glaze from imperfections, fish eyes, etc.