Metallic red, blue, grey, black, green. We can feel that these pots were in fire: the same color shades are present on our heavily-used wood stove.
These two pots were again prepared with groged stoneware and glazed by Raku. The glazes used here contain a lot of metallic particles, iron, titanium or copper… As for the development of black cracks, the reducing atmosphere is used to make these metallic color shades (have a look at “the beauty of crack” in the previous posts).
Copper oxide is green. Pure copper is red. Iron oxide is brown. Pure iron is grey. Titanium oxide is yellow. Pure titanium is grey.
In presence of oxygen, metallic compounds form oxides: copper oxide CuO, iron oxide Fe3O4, Fe2O3 or FeO depending on the amount of oxygen, titanium oxide TiO2 … The oxides are the most common forms of those compounds in natural environment, full of oxygen.
However, by treatment with high temperature and reducing atmosphere, the oxygen is transformed leaving the pure metal element. This is what happened during the Raku glazing, and the development of these beautiful metallic colors.