The Copper Red effect shows the importance of correct firing to achieve a specific effect with certain glaze recipes. The inside of this vase was more heavily and consistently reduced, simply because it was isolated somewhat from the outside kiln atmosphere. The outside of the vase, by contrast, is grey (a product of periods of oxidation during the firing).
|Oxides||CuO - Cupric Oxide|
The color red is very difficult to achieve in ceramics. The most vibrant red within the reach of the average potter is the color produced by copper in reduction firing.