Our Copper Green imitates the patina forming naturally on copper surfaces over time. In the past the roof of a church would turn green shortly after construction, whereas today the change of its color takes much longer. This is due to a better air quality. In acid rain, deriving from the use of coal fired ovens, for example, the copper oxidized faster. In 1929 the mayor of the German city of Cologne, Konrad Adenauer, had a pigment resembling the patina of copper produced. Until today the city is well known for its bridges painted in Cologne Green.